Aluminium Based Metal Matrix Composites

1) The main factor that influences elastic modulus is the matrix , for example : Composites with a aluminium 6061 matrix have a good strength and higher ductility. The reinforcement content is the main factor in the enhancement of elastic modulus in the aluminium silicon metal matrix composite.
The graph below show that aluminium silicon composites with higher strength, because of the increased silicon content, such as 2024/2124 or 7075 Al, had higher strengths but lower ductility. It also shows that the elastic modulus increased with the increase in the silicon content. The matrix type also effects the elastic modulus which typically consists of particulate, nodule or whisker type matrix. (Reference 3)

The yield strength is usually effected by the matrix alloy ,type and the arrangement of the reinforcement effect the strengths of composites, in particular for those which have whisker reinforcement and Ductility tends to decrease with the reinforcement content is increased.
In fracture toughness tests, an increase in particle quantity reduced the toughness of the composites .The main properties which influence the fracture toughness of MMCs is the type of reinforcement, size, shape, quantity and the distribution within the matrix and the toughness of matrix. The poor fracture toughness and fatigue crack growth rate of MMCs is due to low initiation energy for fracture due to high elastic modulus.

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The thermal expansion coefficient of aluminium silicon carbide fibres reinforced material is significantly influenced by the thermal stresses between the matrix and fibres and thermal expansion behaviour relies on the thermal expansion of the fibres. For applications subjected to severe loads or extreme thermal fluctuations such as in automotive components, discontinuously-reinforced metal matrix composites have been shown to offer near isotropic properties
Automotive brake disc and callipers are typically made of cast iron, the use of aluminium silicon MMC, would result in a significant weight reduction of around 50- 60% can be made which helps reduce vehicle fuel consumption and improve overall braking and handling as well as the high thermal conductivity and wear resistance, dimensional stability and excellent cyclic wear properties. Examples of vehicle which have SiC-reinforced aluminium brake disks are vehicles such as the Lotus Elise Volkswagen Lupo. For aluminium composite brake discs to become more common would requires costs to come down and for improved machine ability.
Aluminium MMC shows much higher resistance to wear than the matrix material by its self. The wear of MMC is much more linear than the matrix material by self, and therefore makes it possible to predict wear patterns and the amount of use than can be obtain from a component. The reinforced particles resist the abrasion and restrict the deformation of MMCs which provides a useful guide for better control of their wear. (reference 5)MMC shows much higher wear resistance than the corresponding matrix material; unlike that of matrix material, the wear of MMC is very much linear and possible to predict easily; the wear mechanism is similar for both materials other than the three-body abrasion in the case of MMC; the reinforced particles resist the abrasion and restrict the deformation of MMCs which causes high resistance to wear. These results reveal the roles of the reinforcement particles on the wear resistance of MMCs and provide a useful guide for a better control of their wearMMC shows much higher wear resistance than the corresponding matrix material; unlike that of matrix material, the wear of MMC is very much linear and possible to predict easily; the wear mechanism is similar for both materials other than the three-body abrasion in the case of MMC; the reinforced particles resist the abrasion and restrict the deformation of MMCs which causes high resistance to wear. These results reveal the roles of the reinforcement particles on the wear resistance of MMCs and provide a useful guide for a better control of their wearMMC shows much higher wear resistance than the corresponding matrix material; unlike that of matrix material, the wear of MMC is very much linear and possible to predict easily; the wear mechanism is similar for both materials other than the three-body abrasion in the case of MMC; the reinforced particles resist the abrasion and restrict the deformation of MMCs which causes high resistance to wear. These results reveal the roles of the reinforcement particles on the wear resistance of MMCs and provide a useful guide for a better control of their wear.MMC shows much higher wear resistance than the corresponding matrix material; unlike that of matrix material, the wear of MMC is very much linear and possible to predict easily; the wear mechanism is similar for both materials other than the three-body abrasion in the case of MMC; the reinforced particles resist the abrasion and restrict the deformation of MMCs which causes high resistance to wear. These results reveal the roles of the reinforcement particles on the wear resistance of MMCs and provide a useful guide for a better control of their wear.MMC shows much higher wear resistance than the corresponding matrix material; unlike that of matrix material, the wear of MMC is very much linear and possible to predict easily; the wear mechanism is similar for both materials other than the three-body abrasion in the case of MMC; the reinforced particles resist the abrasion and restrict the deformation of MMCs which causes high resistance to wear. These results reveal the roles of the reinforcement particles on the wear resistance of MMCs and provide a useful guide for a better control of their wearMMC shows much higher wear resistance than the corresponding matrix material; unlike that of matrix material, the wear of MMC is very much linear and possible to predict easily; the wear mechanism is similar for both materials other than the three-body abrasion in the case of MMC; the reinforced particles resist the abrasion and restrict the deformation of MMCs which causes high resistance to wear. These results reveal the roles of the reinforcement particles on the wear resistance of MMCs and provide a useful guide for a better control of their wearMMC shows much higher wear resistance than the corresponding matrix material; unlike that of matrix material, the wear of MMC is very much linear and possible to predict easily; the wear mechanism is similar for both materials other than the three-body abrasion in the case of MMC; the reinforced particles resist the abrasion and restrict the deformation of MMCs which causes high resistance to wear. These results reveal the roles of the reinforcement particles on the wear resistance of MMCs and provide a useful guide for a better control of their wear

From data gathered with the use of the CES software it gave for of the most suitable manufacturing method for a metal matrix component with slots in the design. The above graph so that these four production methods were Laser powder forming, squeeze casting, powder injection molding and die press sintering. Several criteria were considering during the material selection such has relative cost index , production rates , tool life and economic batch size.
looking at the CES data , it showed that the most suitable production method be die cast and sintering. With die casting and sintering a relatively high rate of production can be achieved whilst keeping the relative cost index low. This is important because it helps lower the cost of aluminium MMC brake disc which are still expensive and not used by many manufactures because of this.

Pressing and sintering is a powder processing process that falls in the manufacturing process category of forming .The typical cold pressing and sintering process starts with aluminum silicone MMC in powder being poured into a closed mould. Pressure is then applied to the closed mould at a high enough pressure for the powder to bind together. After the disc is taken out of the mould it is then put through the sintering process. The sintering process begins with the brake disc being heated up in order to burn of any lubricant and is then heated up to a even higher sintering temperature in a protective gas surrounding to prevent oxidization. (reference 2)

4) There has been an increased interest in the use of Aluminium based metal matrix composites in brake discs and drums in recent years. The wear characteristics of AMMCs were high speeds and loads the behaviour could be greatly improved beyond that of cast iron discs, with the correct match of disc and pad material. Casting process is very difficult if reinforcement Material is wet and this can results in non-uniform distribution and poor mechanical characteristics for the finished brake disc. To resolve this problem, reinforcements are pre-heated at 500°C for 40 minutes. Porosity is the major problem in casting which is why moulds are preheated, to 500°C, which helps in removing the gases which are trapped in the slurry to go into the mould. It also enhances the mechanical properties of the cast AMC.  Sorter fibres in a random orientation are typically not as strong as long fibres in a specific orientation. However the use of sort fibres in random orientation means that less human interaction is required in the production and therefore helps brings the cost of production and well as minimising the possibly of something going wrong in the production process my eliminating human error. SiC/Al composites have increased strength with the increase in the silicone content and had higher strengths but lower ductility.

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The use of longer fibres also means that they generally have to be arranged in a specific order which is time consuming and also requires human interaction and this all reduces the number of units that can be produced a day. An example of this carbon ceramic brake disc where the discs which have longer fibres cost significantly more and will only be used in very exotic cars such as Koenigsegg where as more budget sports cars such as Porsche tend to use discs with sort random fibers which are far more cost effective.
1) A. Mazahery, M. O. Shabani . (2012). Mechanical properties of A356 matrix composites reinforced with nano-SiC particles. Available: Last accessed 16/12/2016
2) unknown. (2004). Aluminum Matrix Composites with Discontinuous Silicon Carbide Reinforcement. Available: Last accessed 16 December 2016
3) Ajit Bhandakkar1*, R. C. Prasad1, Shankar M. L. Sastry2. (2014). Elastic plastic fracture toughness of aluminium. Available: Last accessed 16 December 2016.
4) S. Taufik a, ⁎, S. Sulaiman b . (2014). Thermal Expansion Model for Cast Aluminium Silicon Carbide . Available: Last accessed 16 December 2016.
5) Parth S. Joshi, Kiran C. Hegade, Apoorv S. Kulkarni &. (2016). Manufacturing of Disc Brake Rotor Using. Available: Last accessed 16/12/2016.The machinability of an Alî-¸5 Mg alloy reinforced with 5 vol% Saffil and 15 vol% SiC was compared with that of Duralcan (A356) reinforced with 15 vol% SiC. In terms of tool wear and metal removal rate with both cemented carbide and polycrystalline diamond (PCD) cutting tools, it was found that the Duralcan/ SiC was significantly easier to machine than the composite with the Al-5 Mg matrix. This is attributed to the effect of the matrix on the mechanisms of abrasion wear. The machinability of an Alî-¸5 Mg alloy reinforced with 5 vol% Saffil and 15 vol% SiC was compared with that of Duralcan (A356) reinforced with 15 vol% SiC. In terms of tool wear and metal removal rate with both cemented carbide and polycrystalline diamond (PCD) cutting tools, it was found that the Duralcan/ SiC was significantly easier to machine than the composite with the Al-5 Mg matrix. This is attributed to the effect of the matrix on the mechanisms of abrasion wear.

Aluminium Heat Capacities

The aim of the experiment was to determine the specific heat capacities, with uncertainties, of two different materials; for the purposes of this experiment, it was chosen to be aluminium
Specific heat capacity is defined as the quantity of heat energy, which will raise the temperature of unit mass (1kg) of a substance by 1K. It is usually denoted by c and expressed in J/(kg.K). (Joule per kilogram Kelvin).
So, what is the relationship between heat and temperature?
It is usually expressed ΔQ = m c ΔT Heat energy = mass x specific heat capacity x temperature change, (c) being the specific heat capacity. The relationship will not happen if there is a phase change due to heat either being added or removed, does not change the temperature
ΔQ to the change of temperature ΔT is given by: ΔQ = m c ΔT Where ΔQ = the change in heat energy. is the enthalpy, m = the mass c = specific heat capacity ΔT = the change of temperature. Unit: Jkg-1K-1.
High specific capacities occur in substance that take a lot of heat energy and therefore have a long time to heat or cool down. The specific heat capacity of the sea is much greater than the land, so therefore more heat energy will be needed to heat it up by the same amount as the land. From the relationship: mass x specific thermal capacity x temperature / time = current (amps) x p.d. (volts) .The ratio temperature rise or time can be gotten from the graph slope of temperature which was plotted against time and this is how thermal capacity can be met.
Can the chosen method of investigation produce a reliable value for the specific heat capacity of a metal block?
Apparatus: Calibrated thermometer
power pack, Stop clock, Voltmeter
Leads, Balance (up to 1kg),
Ammeter, Immersion heater Test metals
Heat proof matt and lagging
The immersion heater was connected to the power pack, which was set to 10V. The voltmeter and ammeter were set up so that they measured the potential difference and current going through the heater. Next the mass of the sample was recorded using the balance and the immersion heater was placed in the test sample, followed by the thermometer and an initial temperature reading. Simultaneously the power pack was turned on and the stop clock started, and the heater was left to run for two minutes prior to the first recording. Recordings were taken from the voltmeter and ammeter every minute for a total of 15 intervals. The collected data was gathered into a table with the following headings: Following this the data was used to produce a graph of energy against temperature difference, from which the specific heat capacity can be determined.

Original mass: 987.8g


Original temperature, T1: 20oC


Temperature, T2

Temperature change, T2-T1

Voltmeter, V

Ammeter, A

Time, s

Energy, J

































































































Results Table 1:
See graph 3 for a plot of Energy, Q against the temperature difference, T. From this graph the gradient will be determined and the specific heat capacity for the metal found.
Gradient of graph 3:
Specific heat capacity of the metal:
The hypothesis of “Can the chosen method of investigation produce a reliable value for the specific heat capacity of a metal block?” has been met ,more will be said and evaluated below.
Accuracy can be improved by the method of conducting several iterations of the experiment to gather enough information to produce a mean value for the specific heat capacity. Furthermore, the temperature was recorded using a liquid in glass thermometer with an accuracy of +/- 0.5 this lead to percentage errors in the temperature readings ranging from 2.5%- from In order to reduce these errors future experiments will be carried out using more accurate thermometer.  

Dissolving Aluminium Chloride in Water

A controlled variable is a variable that stays the same throughout an experiment such as: adding a specific amount of water to test tubes filled with different amounts of ammonium chloride. An independent variable is the variable that is changed during an experiment, e.g. different amounts of ammonium chloride added to separate test tubes in an experiment. A dependant variable is a variable that changes because of the independent variable, e.g. the difference of temperatures when the first crystals begin forming in the separate test tubes filled with different amounts of ammonium chloride.

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In this experiment the controlled variable will be 10mL of water that is added to each test tube filled with ammonium chloride. The independent variable will be the different amounts of ammonium chloride put into each test tube. The dependant variable will be the temperature of the first crystals appearing in the test tubes filled with different amounts of ammonium chloride that are dissolved in water.
Ammonium Chloride
Ammonium chloride is a substance which has the molecular formula NH‚„Cl and is highly soluble in water. It was first manufactured during the 13th century in Egypt and Europe and was originally known as sal ammoniac. It is used for a variety of purposes. In medicine it is used as an expectorant, which clears the phlegm from the bronchi, lungs and trachea area. It is also used as a component in dry cell batteries, an ingredient in cough medicine and as a dietary supplement to maintain pH levels. (See . Last Updated March 13th 2013.)
Solubility is when a substance is dissolved in a solvent such as water. This is then measured in g/100mL to calculate the solubility of that substance in the solvent, e.g. The solubility of 50g of Ammonium chloride would be shown as 50g/100mL of water. Solubility is a method used to calculate how much of a substance can be dissolved in a solvent. This method can be explained in three different ways: a saturated solution, an unsaturated solution and a supersaturated solution. (See also: Study on Chemistry 1, page 295-96.)
A saturated solution is where no more solute can dissolve in the solvent at a specific temperature.  An unsaturated solution is where more solute can be added to dissolve in the solvent at a specific temperature.  However, a supersaturated solution is where an unexpected amount of solute can still be dissolved in a solvent at a specific temperature. A supersaturated solution can only be achieved (with difficulty) by changing the conditions of the saturated solution.  
In this experiment, the substance is Ammonium chloride and the solvent is water and when mixed together, the Ammonium chloride dissolves. Repeating this with different amounts of ammonium chloride gives us the solubility of Ammonium chloride in g/100mL of water. When adding more ammonium chloride, the max amount of the substance that can dissolve in the solvent is discovered, this is called a saturated solution. If a specific amount of ammonium chloride that always dissolves in g/100mL of water is used, it is called an unsaturated solution because more of the substance can be added to the solvent, to dissolve. If the saturated solution of the substance is reached but more of the substance is added and surprisingly dissolves in the solvent, it is called a supersaturated solution. This experiment can consist of a saturated or an unsaturated solution because the solubility of Ammonium chloride in water is unknown. (See also: URL’s displayed in bibliography with a * next to it)
Solubility Curve
Solubility curve is a graph of solubility vs temperature. Solubility curves are used to predict the maximum amount of a substance that can be dissolved in a solvent at a specific temperature.
A solvent is a substance that is either a liquid, solid or gas that dissolves a solute to create a solution. The maximum amount of a substance that any solvent can dissolve depends on the temperature of the solvent, e.g. If water can dissolve a maximum of 30g of ammonium chloride at 50°C, but the temperature was increased to 60°C it could dissolve more of the ammonium chloride. There are two categories of solvents: polar and non-polar solvents. A polar molecule has two sides; one is positive and the other negative, also known as a dipolar molecule. Polar molecules have polar bonds, though some can have polar bonds but are non-polar molecules. This is because the polar bonds are arranged in a way that they cancel each other out. The overall polarity of a molecule depends on the direction of the bond dipoles in a molecule which is determined by the shape of the molecule.
Polar solvents can have a small electrical charge because of the shape of the compound. A compound such as water has the hydrogen atoms at opposite angles of the oxygen atom. The hydrogen atoms can create a small electrical charge because of the direction of the bond dipoles, which is determined by the shape of the hydrogen atom. A molecule may mix in a polar solvent if it has a polarity of its own. Salt and sugar both dissolve in water easily because their molecules are attracted to the small electrical charges of water. Non-polar solvents don’t have an electrical charge and cannot mix with a polar solvent.
Polar and non-polar solvents use a dielectric constant to provide a rough measure of the solvents polarity. Dielectric constants are the electrical properties of a solvent using a capacitor, in which electrical currents pass through. Non-polar solvents are considered to have a dielectric constant of less than 15. The polarity index measures the ability of a solvent to dissolve different polar materials. The results of both these tests are used in a table of common solvents and in future can be used for identifying solvents in chemical processes. (See also: : Last Updated: 14th March 2013.)
(See also: : Last Updated 14th March 2013.)
Polar and non – polar solvents are related to this experiment because water is a polar solvent and ammonium chloride is a polar solute. This means that the two can mix together. If either one was a non-polar solvent or solute, they wouldn’t mix because they don’t have a positive or negative pole that binds them together.
Endothermic Reactions
An endothermic reaction is where a product absorbs energy from its surroundings, causing its surroundings to drop in temperature. In an exothermic chemical reaction the reactants have more energy than the products. However, in an endothermic chemical reaction the products have more energy than the reactants because it absorbs the energy from the reactants and the environment.
If ammonium chloride is added in a beaker filled with water and dissolved, the beaker would become cold. This is because it is an endothermic reaction, where the ammonium chloride absorbs the energy from the solvent (water) and its surroundings. This is why we heat ammonium chloride, so that more of it can be dissolved in a solvent (water) and the temperature will not drop rapidly. (See also : Last Updated 14th March 2013.)
What is being investigated?
The idea of this investigation is to observe what happens when ammonium chloride is added in a test tube filled with a specific amount of water and heated. The next part of the investigation is to observe what happens when the product is allowed to cool.
How is it being investigated?
This experiment is being investigated by using a range of equipment. An electronic balance is being used to weigh the ammonium chloride and get an accurate result, and a burette to measure an accurate, 10mL of water which is added into a test tube with the ammonium chloride. An electric hot plate is then used to heat up this mixture, and dissolve it while in the process of heating. Next, a retort stand is used to cool down the mixture, so that you don’t have to hold the test tube with your hand since it would be really, really hot! Finally, a digital thermometer is used to get a result of the temperature of when something happens in the test tube, when it is cooling down. These results of the experiment are written down and put into tables and graphs so that others may understand how the results were gathered using these equipment.
How will the results be analysed?
The results will be analysed by finding trends in the statistics that have been written down. These results will then be put into a table and graph. The table will be analysed to investigate if there are any results that don’t fit in and if there is a reason why this result occurred during the experiment. The graph will be analysed by finding if there is a trend between the results on the graph (e.g. a constant) and how they match up. Next, the graph is analysed by checking if there is any inconsistencies or results that seem out of place. Finally, the graph is analysed by testing or checking the results to see if they are correct or incorrect.

solid ammonium chloride
2 retort stands
500 ml beaker
Hand lens
250 mL distilled water
burette holder
large clean test tube
electric hot plate
stirring rod
digital thermometer
2 retort stand clamps
heat mat
electronic balance
black card
safety glasses

4gms of solid ammonium chloride was measured and the actual mass was recorded.
The solid ammonium chloride was put into the large clean test tube.
The burette was filled with distilled water till the level reached 10mL.
This 10mL of water was added to the large clean test tube with the solid ammonium chloride.
300mL of hot water was added to the 500mL beaker.
The beaker was placed on the electric hot plate.
The beaker was heated up to boiling temperature and the large test tube was slowly placed inside with the water level in the beaker 3cm higher than the water level inside the test tube using the retort stand and clamp.
The mixture in the test tube was gently stirred using the glass stirring rod until dissolved.
The large test tube was removed from the beaker after the solid ammonium chloride dissolved and allowed to cool.
The large test tube was stirred and watched using the hand lens and the black card to observe the first crystals form.
The digital thermometer was used to measure the temperature of the first crystals forming.
The mixture was then heated up again and using steps 7 -11 the process was repeated two more times to get the most accurate results of the crystals forming with 4gms of solid Ammonium Chloride.
Steps 1 – 13 was repeated again using 5g, 6g and 7g of solid ammonium chloride.
The results in Table 1, 2 and Graph 1 all have one trend in common; as the temperature increases, the solubility of ammonium chloride increases. This trend shows that the results are reliable but not valid because graph 2, which is the accepted results, shows that the solubility curve of the two graphs do not match i.e. the values do not match but they follow the same pattern. Another trend in the results is the temperature, which shows that for the solubility of ammonium chloride, each gram that was tested roughly differs by 7°C. This trend is neither reliable nor valid because they do not match graph 2 and the patterns in the graph are different.
Saturated, Unsaturated or Supersaturated
These results also indicate that this could be a saturated solution, unsaturated or a supersaturated solution because 4g of ammonium chloride dissolved in water at a temperature of 73.43°C, though the 7g of ammonium chloride dissolved at a higher temperature of 94.56°C meaning that it took longer to dissolve 7g than 4g. This, in turn, shows that if more ammonium chloride was added to the 7g of ammonium chloride it would have taken longer to dissolve and once it passed boiling temperature water would have evaporated till there was no solvent left and there would still be ammonium chloride. This would mean that 4, 5, 6 and 7g of ammonium chloride was an unsaturated solution. This is an error because it is completely different when compared to the result of graph 2. This error means that something occurred during the experiment which made the ammonium chloride at a higher temperature or simply a random error where the water was heated before the ammonium chloride was put into the beaker. This error has significantly changed the result as it has increased the temperature of dissolution when it should be a lot lower.
Comparison (validity and reliability)
Table 1 shows the 4, 5, 6 and 7 grams of ammonium chloride was tested three times to get the most accurate result. These three results were then divided to give an average. The average of the 6 and 7 grams of ammonium chloride in comparison to graph 2 is reliable because the solubility of ammonium chloride increases with the temperature. The average of the 4 and 5 grams of ammonium chloride in comparison to graph 2 could be reliable but the percentage of error is too high for this to be acceptable meaning that there was an error in the consistency of the experiment.
Graph 1: ‘Solubility of Ammonium Chloride’ shows the four averages of each test of ammonium chloride, with a trend-line that predicts the solubility of ammonium chloride between 0°C and 100°C. In addition the graph shows that when you keep adding more and more ammonium chloride the temperature for it to dissolve will increase, but only by a few degrees each time. Graph 2: ‘Accepted Values – Solubility of Ammonium Chloride’ are the accepted values of the solubility of ammonium chloride. In comparison to graph 1, both graphs have a curve, though graph 1 has more curve than graph 2, where the curve is very slight. Graph 1 and 2 do not match at all, meaning that there are errors and/or inconsistences in this experiment.
Table 1, 2 and Graph ‘Solubility of Ammonium Chloride’ all fit the theory that ammonium chloride dissolves in water. When we match up all the results in this experiment, they clearly do not match the accepted values. The accepted values are vastly different as graph 1 shows that 39.99 grams of ammonium chloride dissolves at 73.43°C and graph 2 shows that 39.99 grams of ammonium chloride dissolves at roughly 28.12°C. The results fit the theory because all four tests of ammonium chloride dissolved in water. The only factors that could have changed this outcome could have been the amount of substance in a solvent which is heated to a specific temperature. In the end graph 1 explains as the temperature increases, so will the amount of ammonium chloride that dissolves.
Possible errors that could have occurred during the experiment are: the solid didn’t dissolve properly, temperature could have been wrong during the cooling down process, the recrystallization of the ammonium chloride in water was difficult to judge and malfunction of equipment could have caused errors. The reason why the solid might not have dissolved is because the temperature might not have been high enough or I didn’t stir it enough. In the case of a random error the solid might not have dissolved but the eye might not have been able to see a very small particle even with a small magnifying glass. The reason the temperature could have been wrong is because when I stirred the mixture, the heat from the bottom of the test tube would have mixed with the cool temperature at the top of the test tube, meaning that when you saw the first crystals appearing the temperature could have still been changing. During the experiment the ammonium chloride solution from the first trials was recycled to be used for further trials. This could have changed the purity of the ammonium chloride because it looked very different to the normal ammonium chloride. This could mean that while the weight did not present a problem, it may have not been completely dry which could affect the results. The malfunction of equipment could have occurred without my knowledge, such as the balance scale being inaccurate (e.g. the small empty cupcake cups on the scale did not balance at 0). Another malfunction could have occurred with the thermometer not working properly.
The loss of ammonium chloride not dissolving could have lowered the solubility of the substance. The likelihood of the scale not working is very low and could be counted as a random error, but if it wasn’t working the solubility of the substance would be lower than expected if there was less ammonium chloride and higher if there was more ammonium chloride. The recrystallization could have been the exact same as normal solid ammonium chloride or it could have weighted more or less. This would make the answer higher if the ammonium chloride weighed more than it should. Overall I believe the results and answers I recorded might have been a bit too high or even low, but I definitely know that they aren’t exact. One way to possibly improve the experiment is to use the exact amount of water and ammonium chloride to get a measurement of solubility (g/100mL). This would prove to be more accurate and would be better suited in a beaker, on top of the electric hot plate as the heat would be dispersed around the entire beaker. Further investigations that could be included into this experiment could be finding out the saturated solution of ammonium chloride at a specific temperature. This would be good because it is very likely that every group would get different results and have to explain more in their discussion about errors and if they think that their answer is valid or not.
One way to possibly improve the experiment is to use the exact amount of water to get a measurement of solubility (100mL). This would prove to be more accurate and would be better suited in a beaker placed on an electric hot plate as the heat would be dispersed around the entire beaker. Further investigations that could be included could be finding out the saturated solution of ammonium chloride at a specific temperature. This would be good because it is very likely that every group would get different results and have to explain more in their discussion about errors and if they think that their answer is accurate or not.
In conclusion I discovered that 4, 5, 6 and 7 grams of solid ammonium chloride was soluble in water at different temperatures. The hypothesis that different amounts of ammonium chloride will dissolve in water at varying temperatures was answered. The results that I recorded weren’t valid because they did not match the accepted values, though the results were reliable in some cases as they did have a pattern and this pattern matched the accepted values.

Microstructure of Aluminium Alloy 2618a for Recrystallization


The usage of metallic materials for different purposes by mankind has started from decades (Ferguson, n.d.). There are different types of metals available and their properties are different. The use of metallic materials is inevitable in any field (Hanawa, 2012). Medical, Electrical, Mechanical and in almost every field the use of metals is enormous. The usages of metals differ with respect to their properties. Improvements in the properties of the materials are achieved by chemical, mechanical and thermal processes (Suryanarayana, n.d.). In this study, we are interested in aluminium alloy. The purest form of aluminium is relatively soft and has a yield strength of only 34.5 N/mm2(5,000 lb/in2) and a tensile strength of 90 N/mm2 (13,000 lb/in2) (P.G. Sheasby, n.d.). Most pure materials have relatively low strength. However, it can be improved by certain processes such as alloying, heat treatment, Coldworking etc. Alloying is a process of adding ingredients into the molten aluminium to improve the desired mechanical or chemical properties. The main alloying materials used to improve the properties of the aluminium are copper, magnesium, silicon, manganese, nickel and zinc (P.G. Sheasby, n.d.). The application of aluminium alloy in aerospace application replaces many materials which are not economical. In this research, we are specifically interested in the 2618a alloy which is a 2000 series alloy. 

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 The alloying material use in 2000 series aluminium alloy is copper. The weight percentage of copper usually varies within 1-8 wt% depending upon various applications. They are the main alloy that finds use at elevated temperature. 2000 series aluminium alloys are extensively used in aerospace application due to their properties such as high strength, corrosion resistance, Specific modulus and reasonable ductility. When these materials are used in the aerospace application they are undergone multiple types of loads. In this study, we will be analyzing the microstructure of aluminium alloy 2618a to understand the recrystallization characteristics while undergoing compression loading and how it affects the mechanical properties of the alloy. 

1. Types of Aluminium alloy

 Aluminium alloys are divided into two based on how they are produced, wrought aluminium and cast aluminium. Both are further divided into heat treatable and non-heat treatable alloys. Figure 1 shows the classification on aluminium alloy.

Figure 1 Aluminium alloy classification

The metal which is subjected to mechanical working in the form of rolling, extrusion and forging results in the formation of wrought aluminium. The metal alloys which are prepared using casting is the cast alloys. There is a certain nomenclature procedure to identify the type of heat treatment and temper. The wrought aluminium compositions are generally represented in a four-digit number, whereas the cast composition is represented by a three-digit number followed by a decimal value (Davis, n.d.).

1.1 Properties and composition


Composition and properties


The pure form of aluminium


corrosion resistance, Formable and weldable

Low strength


Principle alloying element– Copper


Strong, Machinable, Fair corrosion resistance

Poor formability and difficult to weld


Principle alloying element- manganese


Corrosion resistant, formable and weldable

Stronger than 1050


Principle alloying element- Silicon


Formable, wear resistant and weldable

Fair corrosion resistant


Principle alloying element- Magnesium


Strong, formable, excellent corrosion resistant and weldable


Principle alloying element- Magnesium and silicon


Strong, formable, good corrosion resistant and weldable


Principle alloying element- Zinc, magnesium and copper


Very high strength and machinability

Fair corrosion resistant and poor weldability

Table 1 Wrought aluminium composition and properties. Adapted from (Davis, n.d.)

Cast Aluminium and its application

The alloy nomenclature for cast aluminium composition is represented in a 3-digit number with a decimal value in the end. The decimal value representing .0 in a cast aluminium represents the alloy limits, decimals 0.1 and 0.2 represents ingot compositions. Table 2 below shows the composition and applications of cast aluminium alloys


Composition and application




High strength

Application at elevated temperature


Silicon is principle alloying element

Copper and/or magnesium are other elements

Used in shape casting


Aluminium-Silicon alloy

Moderate strength, high ductility and impact resistance

Used in bridge railing


Aluminium-magnesium alloy

Moderate to high strength and toughness

Excellent corrosion resistant



Major alloying element is zinc

Copper and/or magnesium are other alloying elements.

Table 2 Cast aluminium composition and properties. Adapted from (Davis, n.d.)

Mechanical behavior of aluminium alloy under tensile loading

Y. Chen studied the stress-strain behaviour of aluminium alloys at a wide range of strain rates. (Y. Chen *, 2008) Automotive industries use a wide range of aluminium and its alloys due to their low weight. Understanding the stress-strain behaviour of the aluminium used in the automotive industry is inevitable since there are numerous tests carried out such as crash test. During the crashworthiness tests, there is a high deformation rate in the structural components. The overall mechanical properties of the materials used have a high significance in the load acting on the components and the energy absorption. Experimental analysis is carried out using the sample specimens of extruded AA6060, AA6082, AA7003 and AA77018 aluminium alloys in T6 temper. These samples are subjected to a wide range of strain rates. High rates of strain are induced using the split-Hopkinson tension bar and standard tensile test machine is used for low to medium strain rates. The experiment is carried out in all three directions with respect to the direction of extrusion due to the anisotropic behaviour of the extruded alloy. It is found from the results that the 6000-series alloy sample shows less sensitivity to the strain rate and the 7000 series exhibits a marked sensitivity in the strain rate. Among the recrystallized alloy AA6060-T6 the strength isotropy is found to be small and for the remaining samples of non-recrystallized alloys, the maximum strength is along the direction of extrusion with a minimum strength in the 45° direction.

3 Strengthening of Metals.

The pure form of metals usually possesses less strength. The strength of the metals are incorporated by mixing with other metals to tailor-made the mechanical properties and this process is called alloying. The ductility of the metal is sacrificed during the strengthening mechanism of the alloy. Numerous hardening techniques are used for improving the mechanical properties and the selection of the alloying metals depends on the application. The strength is incorporated by plastic deformation of the metals due to dislocation. (William D. Callister, n.d.) says “All strengthening techniques rely on the simple principle of restricting or hindering dislocation motion renders a material harder and stronger”.

3.1 Strain Hardening

Strain hardening, also known as work hardening is a strengthening mechanism which will improve the mechanical properties of the material. During strain hardening, the strength of the metals increases when it is plastically deformed. Straining of the materials occurs during cold working at the temperature below the absolute melting point (R. E. Smallman, 1999, p. 226). Metals are having a crystalline structure which has atoms arranged in a closely packed manner in three dimensions. When the metal is loaded the dislocation moves towards the grain boundary. These dislocations are stacked in the grain boundaries results in increasing the dislocation density. As the dislocation density increases, it marks the end of further dislocation and much more external forces are required. This process increases the mechanical properties of the metals such as strength and hardness, but the ductility reduces. When the external forces applied is so high to overcome this the metal will undergo cracking and due to this annealing is done for further working.

3.2 Grain size Hardening

The strengthening mechanism in which the grain size is altered to improve the strength of the metal is known as grain size hardening or hall-petch strengthening. In a polycrystalline metal, the role of grain size or the diameter of the grain is crucial to control the mechanical properties of the metals. When the size of the grain reduced the strength and toughness of the metals are improved. When a metal is plastically deformed tailed by a heat treatment the grain size can be reduced. The rate of solidification from the liquid phase also influence the reduction of grain size. (William D. Callister, n.d.)

3.3 Solid solution Strengthening

 Mixing of copper and tin will result in the formation of a strong metal has been discovered by human five thousand years ago. That was the first alloy created in the world and the process was solid solution strengthening. When a metal is in liquid form (solvent) during the casting process is mixed with a different metal in a liquid state (solute), the strength and hardness of the metal improves (gedeon, 2010). For a unalloyed metal, it is easy for the dislocation to move. When a metal is alloyed, it obstructs the movement of dislocation which required high stress or temperature for it to move. This results in increasing the strength and toughness of the alloy. There are two types of solid solution, Substitutional solution and interstitial solution.

3.3.1 Substitutional solution

In this type of solid solution, the solvent atom in the crystalline structure is replaced with the solute atom. The atoms of the different metals are of a different size which results in the irregularity in the crystal lattice. The movement of the dislocation is interrupted due to this irregularity in the crystal lattice thus improves the strength of the alloy. An example of such process is tin in bronze.

3.3.2 Interstitial solution

Consider the case of carbon in steel, the process is like that of the substitutional solution. In this case, the atoms in solute acquire the interstitial spaces between the solvent atom. When the solute atoms are fits in between the solvent atom in the crystal lattice, the movement of dislocation is restricted. This results in higher stress or temperature for the dislocation to move further.

3.4 Precipitation Hardening

Precipitation hardening is the widely used technique for the strengthening of the metal alloys. They are also called as age hardening since ageing is the main process involved in the precipitation hardening. Majority of the high strength metal alloys are produced by age hardening (skrócie, 2010). Dr Alfred Whilm, German metallurgist discovered age hardening by accident (1903-1909). Commercial alloy named duralumin was the first alloy discovered using this method of precipitation hardening. During the process of age hardening, small precipitates are formed in the second phase particles. The precipitates formed inside obstructs the dislocation to move through the crystalline structure thereby improve the strength of the metal alloys. Steps involved in the precipitation hardening is discussed below.

3.4.1 Solution treatment

The first step involved in precipitation hardening is solution treatment. The alloy is heated to a suitable temperature and socked until a homogeneous solid solution (α) is formed.

3.4.2 Quenching

The process of rapid cooling a metal from the elevated temperature into the room temperature is known as quenching.

3.4.3 Ageing

The material after quenching is subjected to ageing. In this process the material is allowed to precipitate at certain temperature for a fixed time. Aging of material at the room temperature is termed as natural ageing (Fransson, 2009). Ageing at an elevated temperature for the material to precipitate by heating is called artificial aging. The material properties depend on the ageing temperature and time. During ageing, strength and hardness increases to obtain a maximum value and further ageing results in decreasing the strength which is called as over ageing.

4.Optical Microscopy

The microstructure of the aluminium alloy is not visible with the naked eye. The study of aluminium alloy microstructure is necessary to understand the effect of heat treatments and manufacturing in the grain size, grain boundaries etc (Hatch, n.d.). The microstructure can be analyzed by optical microscopy. Optical microscope uses light to get an image of the sample of interest. The method is only limited to the surface analysis, it cannot be used for analyzing the internal microstructure.

4.1 Microstructure and mechanical properties

Kun Yu conducted a research on “mechanical properties and microstructure of aluminium alloy 2618 with Al3(Sc, Zr) phases” (Kun Yu∗, 2003). Scandium and zirconium were added to understand the mechanical properties due to the formation of Al3(Sc, Zr) phases. They compared two alloys, Alloy A with the composition (mass %) Al-2.23, Cu-1.21, Mg-0.93, Fe-1.09, Ni-0.30, Sc-0.30Zr and alloy B which has the same composition as that of 2618AA. The cast billet was hot rolled at 723k and it is cold rolled into sheets of 2mm thickness.The cold process was reduced about 50 and 75% respectively. Some of the specimens were annealed and the remaining were solution treated after the cold rolling. Finally, they were quenched in water and immediately aged at 473 and 573k respectively. The tensile properties of the alloy were measured at 293, 473, 523 and 573K to study how the temperature influences the alloy. The microstructure of the alloy was observed using the optical microscopy, Scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The grain size of Alloy A (about 20–30µm) was found to be smaller than that of Alloy B. Hardness of Alloy B decreased significantly in the temperature range from 473 to 573 K due to the recrystallization during the annealing. The recrystallization temperature of Alloy A is found to be about 200K higher than that of AA2618. The grains of the Alloy A containing scandium and zirconium were refined. The thermo-stable Al3(Sc, Zr) particles impeded the nucleation of recrystallization grains and retarded their growth. The ambient and elevated temperature strengths of Alloy A were greater than those of Alloy B. The yield strength and ultimate strength of Alloy A increased by about 80 MPa at ambient temperature and 40 MPa at 573 K with almost no ductility changes. Alloy A had many double-layer of Al3 fully coherent with the Aluminum matrix. It was found that high coherent strain energy existed in the matrix around the Al3(Sc, Zr) particles and produced a coherent strengthening. Also, the size of the precipitates of Al3(Sc, Zr) were small and dispersed, providing large force to retard the movement of dislocations and increase the alloy strength. Thus, strength of the alloy increased without a change in ductility.

4.2 Grain refinement

Rosmamuhamadani Ramli conducted a research on “Microstructure and mechanical properties of Al-Si cast alloy grain refined with Ti-B-Sr-Sc-Mg” (Arawi, n.d.). The microstructure is an important factor which defines the mechanical properties of an alloy. Grain refiners are added to improve the microstructure of the alloy. The coarser grain size results in deteriorate the mechanical properties. Silicon is used as an alloying element because of its excellent casting characteristics. Permanent mold casting method is adopted for the cast aluminum alloy preparation. The method is suitable for producing material with the good surface finish and dimensional tolerance. The molten material is cooled in the cavity of the mold with a controlled cooling rate for avoiding any inherent defects during the manufacturing process. Alloys of four sample with weight percentage varying from 0.02 to 0.08 of Sc is used and the hardness test result of the alloy samples shows that hardness increases as the weight percentage of Sc increases. Tensile stress and hardness of 399.4 Mpa and 95.8 respectively are found for the sample contains 0.08 wt% of Sc.

5. Microalloying

Purnendu Kumar Mandal conducted a study to understand the effect of addition of Ag(silver) on the hot deformation behavior of 2219 Al-alloy containing 0.1 wt % Ag prepared by casting technique. Aluminum-1100 alloy (99% pure) ingot, International Annealed Copper Standard grade copper rod, and sterling silver (92.5% pure) were used to prepare Al-42 wt % Cu and Al-5.8 wt % Ag master alloys by melting followed by solidification in metal ingots (Mandal, 2018). The required quantities of the Al ingot and master alloys were then heated in a clay graphite crucible using a resistance heated melting furnace. The molten metal was subsequently poured at 700˚C into sand molds to obtain cylindrical rods of the two alloy compositions, i.e., 2219 Al alloy (alloy-A) and 2219 Al+0.1 wt % Ag alloy (alloy-B). Cylindrical compression specimens were then machined from these rods. Composition analysis of both the alloys was determined by atomic absorption spectrophotometer. The samples were heated up to test temperature inside a resistance heated split furnace and uniaxial compression tests were carried out at different temperatures and constant true strain rates, using a dynamic 100 kN capacity universal testing machine. From the stress versus strain plots, the peak flow stresses for each test conditions were determined. The predicted and experimental values of peak flow stresses were well in agreement. Plastic deformation was accompanied by rapid dislocation multiplication resulting in work hardening leading to a rapid rise in the flow stress. As dislocation density increased with further deformation, dynamic softening occurred affecting work hardening. Due to this, the flow stress increased at a decreasing rate until it attained a peak value. With further increase in strain, the flow stress almost remained constant indicating a balance between work hardening rates and softening rates. The value of flow stress was less in alloy B. Samples after hot compression test were water quenched, sectioned parallel to the load axis using a precision saw, polished using variable speed grinder-polisher and were etched by dipping in freshly prepared Keller’s reagent for 8–15 s. The etched specimens were observed under an upright optical microscope. Investigation of the flow curves and microstructure revealed that dynamic recrystallization is responsible for the continuous flow softening behavior at high temperature and low strain rate. It can be taken from this work that, at low temperature and high strain rate, deformation is accompanied by deformation band formation. It was also observed that the flow stress for hot deformation of 2219 Al alloy decreased with the addition of 0.1 wt % silver. Silver addition resulted in flow softening of the 2219 Al alloy at elevated temperature. Addition of 0.1 wt % silver in 2219 alloy resulted in decrease in the activation energy (Q) for deformation in the range of strain rates and temperatures.

6. Recrystallization

Liangming Yan, conducted a research on the “Dynamic recrystallization of 7055 aluminium during hot deformation” (Liangming Yan1, 2010). They used an ingot of 7055 alloy of dimension Փ10mm X 15mm for hot compression loading of strain rate 1.0 X 10-2 and 1.0 X 10-1 s-1 and a maximum strain of 0.7. Hot compression was conducted at a temperature ranging from 350-450 degree Celsius. The deformed material was evaluated using the Electron backscatter diffraction (EBSD) which uses the principle of electron diffraction to understand the microstructure of the specimen. At temperature of 400 °C, the grain boundaries extensively became serrated and bulging, along which a few small dynamically recrystallized grains had already been developed. At a nominal strain of 0.7, the amount of new recrystallized grains had further increased, and the size of new recrystallized grains had also increased. At temperature of 450 °C, bulging was hardly observed under OIM micrographs at a strain of 0.3. The original grains were elongated evidently and sub grain boundaries increased with increasing strain. At a strain of 0.7, bulging was observed but dynamic recrystallization grains did not appear. At high Z value, the grain boundaries extensively became serrated and bulging, along which some small dynamically recrystallized grains had developed. At lnZ value of 23.2, the low angle boundaries decreased, and diameter of dynamically recrystallized grains increased. The amount of dynamically recrystallized grains was observed to be less than that at the high Z value. With increase in Z, the amount of dynamically recrystallized grains had increased. The initiation of DRX began with continuous dynamic recrystallization (CDRX) which involved the transformation of low angle boundaries into high angle boundaries. It is observed that the DRX nucleation of 7055 aluminum alloys can be operated by bulging of the original grain boundaries, which is assisted by sub grain rotation. Also, deformation condition (Z value) has a great influence on the nucleation mechanisms of DRX in 7055 aluminum alloy. Discontinuous dynamic recrystallization (DDRX) happened at lower deformation temperature leading to nucleation of DRX in the alloy. During deformation at lower temperature, dislocation movement became difficult. The second phase particles, including the un-dissolved particles during homogenization and the precipitate on the hot deformation prevented the movement of dislocation. It was observed that DRX happened when distortion energy formed by dislocations stress field reach the energy of developing dynamic recrystallization. The microstructure of the deformed material showed that the fraction of the new grain increased with the Z value. The stress-strain curve obtained from the compression test show curves, where it is found that the true stress increases with decreases in temperature. The curve of 1.0×10-2s-1 of strain rate shows the stress increases as with respect to increasing in strain and after a point, it shows steady region. From this analysis, they found that the deformation condition has great influence on the nucleation mechanism of the dynamic recrystallization in 7055 aluminum alloy.


Arawi, *. R. *. K. T. Z. O., n.d. Microstructure and mechanical properties of AL-Si cast alloy grain refined with Ti-B-Sr-Sc-Mg.. 2011 IEEE Colloquium on Humanities, Science and Engineering Research (CHUSER 2011), Dec 5-6 2011, Penang.

Davis, J., n.d. Aluminum and aluminium alloys. ASM International.

Ferguson, C., n.d. Historical Introduction to the Development of Material Science and Engineering as a Teaching Discipline, s.l.: UK centre for materials education.

gedeon, M., 2010. Solid solution hardening and strength, s.l.: Brush wellman alloy products.

Hanawa, T., 2012. Research and development of metals for medical devices based on clinical needs. Science and technology of advanced materials.

Kun Yu∗, W. L. S. L. J. Z., 2003. Mechanical properties and microstructure of aluminum alloy 2618 with Al3(Sc, Zr) phases. Materials Science and Engineering A368 (2004) 88–93.

Liangming Yan1, a. S. J. L. Z. L. Z. T., 2010. Dynamic Recrystallization of 7055 Aluminum Alloy During Hot Deformation. Materials Science Forum Vol. 650 (2010) pp 295-301.

P.G. Sheasby, R. P., n.d. The Surface Treatment and Finishing of Aluminum and Its Alloys. ASM International, Issue 6.

R. E. Smallman, R. J. B., 1999. Work hardening. In: Modern physical metallurgy and materials engineering. s.l.:Reed Educational and Professional Publishing Ltd 1995, 1999, p. 226.

skrócie, W., 2010. Total materia, Precipitation Hardening of aluminium alloy. [Online] Available at:

Suryanarayana, C., n.d. Mechanical alloying and milling. Progress in material science.

William D. Callister, J., n.d. Materials Science and Engineering, An Introduction. 7th ed. Utah: s.n.


Recycling Aluminium into Alum Crystals

This experiment was designed to recycle aluminium into alum crystals which have uses in industry. The aluminium was converted to alum by heating the metal samples with potassium hydroxide solution. The product was then reacted with sulphuric acid followed by crystallization. Overall, five trials were conducted with the only variable being the mass of aluminium used. The mass of crystals produced increased until the trial of 0.9g, when excess aluminium was observed. These different aluminium masses consisted of 0.3g, 0.5g, 0.7g and (2x) 0.9g.
These particular research questions will be answered throughout this EEI:

How the mass of the scrap aluminium related to the final mass of the alum crystal?
How can stoichiometry of a sequence of chemical reactions be used to calculate the percentage yield of alum synthesized from aluminium scrap?
How can scrap aluminium be chemically converted into a crystal?
How does converting aluminium to alum make a worthy recycling process (make use in society, is it financially sustainable?).

Background Information
Alum is a salt that in chemistry is a combination of an alkali metal, such as sodium, potassium, or ammonium and a trivalent metal, such as aluminium, iron, or chromium. The most common form, potassium aluminium sulfate, or potash alum, is one form that has been used in food processing.
Modern beverage containers are usually composed of aluminium, in the form of aluminium cans. Australians consumed over 3 billion aluminium cans in 2005. Additionally, approximately 300 million aluminium beverage cans are produced each day in the U.S. Recycling has the benefit of reducing litter from discarded cans and a number of states have passed laws requiring a deposit on aluminium cans to encourage recycling.

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In this experiment, instead of recycling scrap aluminium into new metal cans, a chemical process will be used that converts scrap aluminium into a useful chemical compound, potassium aluminium sulfate dodecahydrate, KAl(S04)2 ï‚· 12H20, commonly called “alum”. Alum is widely used in the dyeing of fabrics, in the manufacture of pickles, in canning some foods, as a coagulant in water purification and waste-water treatment plants, as well as in the paper industry.
In an aqueous solution of KAl(SO4)2 ,the K+, Al3+, and SO22- are surrounded by molecules of water (they are hydrated). These ions do not have an orderly arrangement in solution. When the compound is forced to crystallize, the ions must begin to join each other in their characteristic order. This process of nucleation may occur spontaneously when the ions of alum collide with appropriate orientation and with sufficiently low kinetic energy to permit them to “stick” to each other and prevent them from rebounding. Occasionally, some foreign solids (irregularity on the wall of the container, dust particles) will serve as nuclei (or starting points) for the formation of crystals. Once a tiny crystal has formed, ions in their random motion through the solution will hit the faces of the crystal, join the orderly array of ions, and make the crystal grow. There is ionic bonding, covalent bonding and intermolecular attractions, plus hydrogen bonding, which is the attraction between water molecules. The only type of bonding not present in potash alum is metallic bonding.CAS_GIF_7784-24-9.gif
Aluminium, like almost all metals exhibits “metallic bonding”. It can be oversimplified by saying that metallic bonding is like having positive metal ions in a sea of mobile electrons. The mobile electrons are the loosely held valence electrons that can easily move from atom to atom.
In fact, metals behave more like atoms which share orbitals to form delocalized covalent bonds. Orbitals from adjacent metals atoms overlap side-to-side to form pi- bonds.
For example, in this diagram, each iron atom, (and the same is true for aluminium) exhibits side to side overlap of the orbitals making pi bonds. Only one axis is shown in the diagram, but overlapping of the atoms in front of and behind this line also occurs. The beauty of this is that the electrons can move along the pi-bonds, from atom to atom, allowing the metal to conduct electricity.
Potassium alum is hydrated potassium aluminium sulfate KAl(SO4)2*12H2O. Since all chemical bonds are essentially covalent in nature, then this compound contains covalent bonds as well. The potassium-sulfate bond is the most polar, and the most ionic-like of the bonds. The substance crystallizes in a face-centred cubic arrangement of hydrated K and Al atoms alternating with SO4 radicals. Despite being a vast oversimplification of a complex structure, there are ionic bonds between K and SO4 and Al and SO4, and there are covalent bonds within SO4. This allows an electrostatic attraction between the polar water molecules and the ions.
Although aluminium is a “reactive” metal, it reacts only slowly with dilute acids because its surface is normally protected by a very thin, impenetrable coating of aluminium oxide; such metals are referred to as self-protecting or passivating metals. Alkaline solutions, or bases, (containing OH-) dissolve the oxide layer and then attack the metal:

AL2O3(s) + 2NaOH(aq) + 3H2O(l) ———> 2NaAl(OH)4(aq)
2AL(s) + 2NaOH(aq) + 6H2O(l) ———> 2NaAl(OH)4(aq) + 3H20(g)

Thus, in aqueous alkaline medium, aluminium is oxidized to the tetrahydroxoaluminate anion which is stable only in basic solution.
Aluminium is obtained from a raw material called bauxite predominantly in Latin and South America, Africa, and Australia. Recent technological improvements have seen the energy cost of producing one tonne of aluminium drop to 15,000 kW, but that is still a lot of energy on top of which must be added, the energy of transporting the metal obtained around the world. Therefore aluminium recycling is extremely important and very easy for everyone to do.
Because of the energy used during extraction of aluminium from bauxite, aluminium is the only commonly used packaging material with a value that exceeds the financial costs of recycling it. To recycle an aluminium can, it costs only 5% of the energy used to create it in the first place. Additionally, aluminium can be recycled many times without any loss in quality.
The aim is to investigate the effect of the amount of scrap aluminium on the amount of alum crystal produced when the amounts of potassium hydroxide and sulphuric acid used are kept constant.
It was hypothesized that if the weight of the scrap aluminium is increased or decreased then the amount of the alum crystal will adjust accordingly, when potassium hydroxide and sulphuric acid are kept the same.

Potassium hydroxide, KOH, 1.0 M solution
Sulphuric acid, H2SO4, 6 M solution


Aluminium beverage can
Beakers: 3x 50-100mL, 3x 250mL, 3x600mL
Bunsen burner
Buchner funnel
Filter paper
Stirring rod
Graduated cylinder

Independent Variables
Independent Variables are those that are changed on purpose. The Independent Variables of this experiment are:

The mass of the scrap aluminium

Dependent Variables
The Dependent Variables are the factors that change according to the independent variables. The Dependent Variables of this experiment are:

The amount of alum crystal produced
The size of the alum crystals

Controlled Variables
Controlled Variables are the variables that are kept constant during the entire experiment. The controlled variables of this experiment are:

Amount of potassium hydroxide poured into the beaker
Amount of sulphuric acid poured into the beaker
Same size beakers for all five experiments

Uncontrolled Variables
The uncontrolled Variables are those that cannot be kept regular and may affect the validity of the experiment. The uncontrolled variables of this experiment are:

The impurity of the scrap aluminium

Risk Factors
Before the procedure can be commenced, certain safety precautions must be implemented prior to the beginning of the experiment. First of all Alum is non-toxic, although alum solutions can cause eye irritation (potassium hydroxide solutions are caustic). Therefore it is crucial to wear goggles or safety glasses when working with the solution. It is essential that the growing solutions are stored in a safe environment and not be disturbed. In the event of contact with skin or eyes (with any of the solutions – especially sulphuric acid which is highly corrosive), the affected area must be washed immediately with lots of water. If necessary, medical assistance should be obtained. Sulphuric acid is corrosive. The aluminium metal may have sharp edges, so it must be handled with care. Before handling any beakers, they must be inspected for any chipped or sharp edges, which may cause injury. Bunsen burners can be very hazardous due to its roaring flame so it must be used with caution. The flame must not be anywhere near the rubber hose because it can be easily melted. As long as all chemicals are kept distant from the human body, the Bunsen burner, and any other dangerously reactive materials, safety will be optimized.
A piece of aluminium was scraped with sandpaper to eliminate the strong, thin aluminium oxide layer.
The mass of the clean piece of aluminium was carefully measured; 0.300g (+/- 0.001g).
The aluminium piece was then cut into smaller pieces, allowing larger surface area for the following reaction.C:UsersGeorgioDesktopSchoolChemistryMaterials Assignment – Yr 11Photos18052010030.jpg
These smaller pieces of aluminium were then placed in a 250mL beaker, with an added 50mL of 1M KOH (potassium-hydroxide).
A Bunsen-burner was then used to heat up the solution to boiling point, to completely dissolve the aluminium (a stirring rod is useful for enhancing the rate of reaction).
Once the aluminium was completely dissolved, the solution was then filtered using filter paper, removing insoluble impurities.
After being filtered, 20mL of 6M H2SO4 (sulphuric acid) was then added to the solution.
Immediately white crystals began to form in the solution.
The alum was removed from the liquid by filtration.
The alum was then left for 24 hours to crystallize.C:UsersGeorgioDesktopSchoolChemistryMaterials Assignment – Yr 11Photos18052010039.jpg
The filtration paper was then placed under a heat lamp to rid any condensation or leftover moist on the paper.
The weight of the final alum crystal was then able to be defined by subtracting the original weight of the filtration paper from the weight of the filtration paper with the alum.
This resulted in a final given amount of produced alum crystal.
REPEATED STEPS 1-13 (x4) with weights of scrap aluminium; 0.5g, 0.7g, 0.9g (2x)
Amount of alum produced:
Beginning Amount of Aluminium
Amount of Alum Crystal
At temperature, 100 parts of water dissolve (g/100ml):
Potash Alum
Beginning weight of aluminium piece
Amount of alum produced (g)
Starting weight of aluminium
Percentage Yield for alum experiments
Solubility of potash alum in water:
Amount of books containing alum:an17-4a.gif
Consumption and Recycling of aluminium can beverages in the world:
Experiment Yield
Theoretical Yield:

2Al(s) + 2KOH(aq) + 4H2SO4(aq) + 22H2O(l) ——> 2KAl(SO4)2•12H2O(s) + 3H2(g)
According to the chemical reaction, 2 moles of aluminium will react to form 2 moles of alum.


Theoretical yield = Mass of aluminium used = Mass of Alum obtained
Molar mass of aluminium Molar mass of Alum
Percent yield = Mass of alum obtained x 100
Theoretical yield of alum

0.3g Aluminium:
0.300 = X 3.769 x 100 = 71.6
27 474 5.26
= 5.266
The percentage yield is 71.6%
0.5g Aluminium:
0.500 = X 4.913 x 100 = 56%
27 474 8.77
= 8.77
The percentage yield is 56%
0.7g Aluminium:
0.700 = X 7.878 x 100 = 61.55
27 474 12.8
= 12.8
The percentage yield is 61.55%
0.9g Aluminium (trial 1):
0.900 = X 8.763 x 100 = 55.46
27 474 15.8
= 15.8
The percentage yield is 55.46%
0.9g Aluminium (trial 2):
0.900 = X 4.437 x 100 = 28.08
27 474 15.8
= 15.8
The percentage yield is 28.08%
From the results obtained, it can now be determined how the mass of aluminium affects the alum crystal mass and size. After making all recordings, different qualitative and quantitative results were questioned. As seen from the results obtained in “5.0 Results”, there were two trials for the experiment with the mass of 0.9 grams of aluminium. This was decided because it was apparent that at around 0.9g of aluminium, it would begin to cause the solution to be saturated. Therefore the procedure for these two experiments differentiates in the following way; as with the other experiments, one was filtered after adding the sulphuric acid (creating the alum), and the other was left to crystallize with no further process. These both resulted in a successful and an unsuccessful result, which provided qualitative results. The one that was filtered had completely crystallized within 24 hours. The one that was left in a solution with aluminium was left to crystallize. The alum did not precipitate from this solution. This result was an anomaly for the experiment for it gave dissimilar results which were discarded. The same procedure was successful until 0.9g due to the fact that the aluminium was acting as the limiting reagent. At 0.9g the potassium hydroxide became the limiting reagent allowing the aluminium to serve as the excess reactant.C:UsersGeorgioDesktopSchoolChemistryMaterials Assignment – Yr 11Photos19052010040.jpg
These were all the chemical equations step by step during the procedure:
When sulphuric acid is slowly added to an alkaline solution of this complex anion, initially, one hydroxide ion is removed from each tetrahydroxoaluminate anion causing the precipitation of white, gelatinous aluminium hydroxide, Al(OH)3
2K[Al(OH)4](aq) + H2SO4(aq) → 2Al(OH)3(s) + K2SO4(aq) + 2H2O(l)
The excess potassium hydroxide is neutralized by some of the sulphuric acid to form potassium sulfate.
2KOH(aq) + H2SO4(aq) → K2SO4(aq) + 2H2O(l)
On addition of more sulphuric acid, the aluminium hydroxide dissolves forming the hydrated aluminium cation
2Al(OH)3(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 6H2O(l)
Addition of alkali to the Al(OH)3 precipitate will also bring about dissolution by reforming [Al(OH)4]. A hydroxide, such as aluminium hydroxide, that can be dissolved by either acid or base is said to be amphoteric. When the acidified aluminium sulfate solution is cooled, potassium aluminium sulfate dodecahydrate (“Alum”) precipitates.
Al2(SO4)3(aq) + K2SO4(aq) + 24H2O(l) → 2K[Al(SO4)2]•12H2O(s)
The overall reaction that takes place is the sum of the previous reactions.
2Al(s) + 2KOH(aq) + 4H2SO4(aq) + 22H2O(l) → 2KAl(SO4)2•12H2O(s) + 3H2(g)
All of the filter papers that were to be used were weighed, and an average filter paper mass was recorded for later purposes. For each of the alum solutions that were produced, once filtered (excluding the one that wasn’t filtered), were then given 24 hours to crystallize before data and measurements were recorded. It was apparent that in the beaker that contained the solution of the filtered alum, there were small crystal seeds that had formed. This was due to the saturated solution which still contained alum, therefore in the 24 hours it was able to grow into bigger alum seeds. The remaining liquid in all the beakers was decanted leaving only the crystals; they were placed under heat lamps for 10 minutes to evaporate any adhering water. Some final results from the measurements were now conductible. Knowing the beaker mass, the beaker mass with alum, the filter paper mass and the filtration paper mass with alum, the amount of alum produced was established. These final crystal masses were:

0.3g = 3.769g (+/- 0.004g)
0.5g = 4.913g (+/- 0.004g)
0.7g = 7.878g (+/- 0.004g)
0.9g = 8.763g (+/- 0.004g) (with filtration paper)
0.9g = 4.437g (+/- 0.002g) (without filtration paper)

It is quite obvious to state that a trend in this experiment was recognized after noticing that (as stated in the hypothesis) when more aluminium is used, more alum crystal is produced, so long as the aluminium remains the limiting reagent. As the aluminium mass increases, the alum product remains at a fairly relative mass for all four scenarios.
In reference to the results obtained from “5.3 Experiment Yields”, it was found that the percentage yield for all experiments (excluding the non-filtered one) were relatively impressive, but predictable. In practice, getting 100% yield is incredibly difficult if not essentially impossible. Often reactants or products can be lost to the environment, not all of the reactants could react or other factors could impede the reaction. Although in this experiment, a different factor was the cause of the loss of yield percentage. The manufacturers of aluminium cans use an aluminium alloy when making the cans, therefore causing the aluminium to have impurities. This was also noticeable when the reaction of the aluminium with the potassium hydroxide took place; the black residue which was produced was the sign of impurity. A procedure which could have helped prevent this error would have been to soak the aluminium in NaOH (sodium hydroxide) which would get rid of the oxide layer that the aluminium contains and any other impurities. Another possible solution to increasing the percentage yield would be to immediately put the beaker in water and ice, straight after adding the sulphuric acid to the solution; allowing it to chill thoroughly for about 15 minutes. Considering this solubility data, some product will not precipitate from the solution. Considering this table and graph (shown in Results), an improved result would be obtained by precipitation in ice water. This would cool the solution down much faster allowing the crystals to grow at a much greater reaction rate. Whereas when it isn’t iced, but filtered immediately, much of the alum saturated solution will fall through into the beaker losing some content. Furthermore, when the alum crystal was being handled (transport to filter paper from beaker, etc.) alum would have been eluded. The consequence of this would result in less alum.
This experiment aimed to investigate the effect of the amount of scrap aluminium on the alum crystal, when potassium hydroxide and sulphuric acid were kept constant. Regarding the outcome of each trial, the results were supported by the theory stated in the hypothesis: It was hypothesized that if the weight of the scrap aluminium is increased or decreased then the amount of the alum crystal will adjust accordingly, when potassium hydroxide and sulphuric acid are kept the same. It was found that the aluminium’s mass had a definite effect on the amount of alum produced. It can be concluded that when the potassium hydroxide is kept constant as well as the sulphuric acid, the outcome will be relatively similar and will adjust accordingly to the weight of the scrap aluminium.
The crucial errors which were encountered in this experiment, which had a vast impact on the percentage yield, was the impurity of the scrap aluminium, the imprecision of handling the alum, and the improper cleaning procedure which was undertaken with each of the scrap aluminium pieces.
The results obtained prove the hypothesis correct which stated that if the weight of the scrap aluminium is increased or decreased then the amount of the alum crystal will adjust accordingly.
Alum Crystals. (n.d.). Retrieved May 21, 2010, from Buzzle:
Alum Synthesis. (2005, June). Retrieved April 29, 2010, from Chemistry 111 Laboratory:
Aluminium Potassium Sulphate. (n.d.). Retrieved May 05, 2010, from Chemical Land:
Aluminium Sulphate. (n.d.). Retrieved May 22, 2010, from Bisley:
Bentor, Y. (2010, May 31). Periodic Table: Aluminium. Retrieved 14 May, 2010, from Chemical Elements:
Chemical of the Week. (n.d.). Retrieved May 26, 2010, from Science is Fun:
Growing Crystals of ALum. (n.d.). Retrieved May 16, 2010, from Princeton University:
Helmenstine, A. M. (n.d.). Aluminium or Aluminium Facts. Retrieved May 08, 2010, from About:
Katz, D. A. (2000). Alum from Waste Aluminium Cans. Retrieved April 22, 2010, from
Katz, D. A. (2000). Growing Alum Crystals. Retrieved May 12, 2010, from Chymist:
Potash Alum. (n.d.). Retrieved May 14, 2010, from Encyclopedia – The Free Dictionary:
Potassium Alum. (n.d.). Retrieved April 30, 2010, from Paul’s Lab:
POTASSIUM ALUMINIUM SULFATE. (n.d.). Retrieved May 25, 2010, from The Royal Australian Chemical Institute Incorporated:
Preparation of Alum. (n.d.). Retrieved May 11, 2010, from
Winter, M. (n.d.). Aluminium. Retrieved May 18, 2010, from Web Elements:

Aluminium Wings v Composite and Future Wing Materials

The comparison of the properties of the materials used in aluminium and composite wings and the advantages and disadvantages of which they both possess and make them suitable for use within the manufacture of wings. A discussion of future materials which have been developed and are suitable for the use in wings will also take place. Collected information came from appropriate websites and books.

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Aluminium is the widest used material for the manufacture of aircraft wings to date since the first time it was used in the 1920’s. Now the use of composites is becoming greater utilized in the manufacturing of aircraft wings at present instead of traditional aluminium wings. This is mainly to do with the weight saving properties that composites can posse. Weight saving properties is just one of the advantages of composite materials, another can be stiffness, but there are also disadvantages to using composites compared to aluminium, such as if they get damaged they need replacing immediately unlike aluminium which is very tolerant to damage. Aluminium production and repair is also much easier than that of composites. Aluminium and composites both have their own advantages and disadvantages and their properties have to be taken into account before any material changes are made. Future developments will hopefully provide a material that which will provide sufficient advantages and minimal disadvantages compared over composites or aluminium.
This report will look at the Boeing 737, which features aluminium wings, and the Boeing 787 dreamliner, which incorporates composite wings, and refer to them for the comparison of the different properties and structures of the two wing types. It will look at each type of material found in a traditional aluminium aircraft wing structure at present and will go into depth about the use of composites in wings instead of aluminium at present and in the future. The types of composites used, as well as investigating whether the structure of the wing had to be altered to compensate for the different properties of the composites will be discussed. The strength and weight properties of each different type of aluminium and composites used in an aircraft wing will also be examined. Types of corrosion which occur on an aluminium wing, including the inspection and repair of it will also be included, as well as the inspection and repair of composite materials and the types of damage which can occur in composites, such as delamination. The cost of production and repair of composites compared to aluminium and aluminium alloys, as well as the weight saved resulting in lower running costs for the company will be examined. The collected information will then be compared and advantages and disadvantages of each type of wing will be produced. It will also look at future aircraft wing materials, such as the use of incorporating aluminium with composites, and if they will change the way aircraft looks at present. The different properties of the new materials will also be examined and compare to the properties of both aluminium and composite wings. An overall conclusion of all the main findings and collected information will also be given. Recommendations will also be given at this point.
After deciding what the topic of the report was going to be about, the research undertaken would need to be relevant. The first part of the study was to find information about Aluminium wings and the materials and structures which made them. This part incorporated finding and recording relevant information from certain websites off the internet. Another source used was finding appropriate books which gave suitable information about the subject in hand. Finding information on composite materials and structures was carried out by the same method. Locating appropriate information about future aircraft wing materials was carried out only with the use of the internet.
Aluminium wings
Aluminium (Al) has been used in aircraft since the 1920’s due to it being lightweight while also being relatively strong. It is used over steel as aluminium is three times the density less then that off steel, this means that for the same density the aluminium would be three times thicker, resulting in it being much stronger. Aluminium is also has good corrosion resistance, which is an advantage as an aircraft is subject to all weather conditions. Nowadays aluminium is joined with other elements to change the properties of the metal, improving specific areas of it, creating an aluminium alloy. At the present time, Aluminium alloys make up a vast total of a commercial aircrafts unloaded weight.
Adding different elements to aluminium improve different properties, for example adding zinc to aluminium will improve the strength of the material. The added zinc allows the aluminium to be heat treated, where the metal is heated and cooled which in turn changes the structure of the metal along with its properties. More than one element can be added at the same time resulting in different properties being produced from having the same main alloying element. Even tho some of the properties of the aluminium will improve, the alloying elements need to be correctly chosen as other properties within the metal will be sacrificed. Certain aluminium alloys are used in the manufacturing of aircraft wings, the types of aluminium alloys, along with where it is used, the elements which are used to create the alloy and the improved properties are listed in the table below.
Al Alloy
Area Used
Elements (%)
Spars, Beams, upper wing skin
Zinc, magnesium, copper
High compressive strength to weight ratio
Lower wing skin
Zinc, magnesium, copper
Improved stress corrosion and fatigue resistance
Wing ribs
Improved stress corrosion cracking resistance, high mechanical properties
Slats, flaps
Good fatigue performance, fracture toughness, slow propagation rate
The Boeing 777 also uses the aluminium alloy 7055 due to it having a greater compressive strength than other alloys that had been tried before. Due to this, it was able to be used in the manufacture of parts of the wing, in the stringers and the upper wing skin.
Even though Aluminium has good corrosion resistance, it is still susceptible to corrosion. Aluminium is somewhat protected from corrosion as an aluminium oxide film forms on the surface. This is due to the aluminium being protected from additional oxidation by the existing aluminium oxide film. Minimal corrosion, such as light surface or small pitting corrosion, does not normally cause a problem to the metal. Heavier corrosion occurring in metals used on aircraft is not wanted as it can lead to a weakening in the structural rigidity of the metal. If this is not rectified it can lead to a structural failure within part of the aircraft. Corrosion can occur in many different forms, which include pitting, intergranular, and galvanic corrosion.
This is one of the main types of corrosion which occurs on an aircrafts wing. This type of corrosion is a localised type and starts on the surface of a metal, whether it is on the skin panels of the aircraft or within the aircraft itself. It works its way through the surface protection of the metal, and then penetrates its way further into the metal creating a hole within the metal itself. Due to metals have different mechanical and chemical properties, when pitting corrosion occurs, the pits created will be different from one metal to another, as shown in on the right. This hole decreases the strength of the metal due to the grain damage caused by the pitting corrosion.
One way of detecting certain corrosion is by using x-rays or gamma rays to take a picture of the piece of metal suspected of having corrosion. Once the picture is developed, it is clear to see where the corrosion, such as pitting, is taking place in the metal, as it produced a darker spot on the film. This is due to less of the radiation being absorbed where the corrosion is taking place. If pitting corrosion is taking place, the image can be used also to establish the depth of the pit within the metal.
Another way of determining whether pitting corrosion has occurred on a piece of metal is by the use of Eddy currents. This type of non-destructive testing uses magnetic fields, where the metal object being tested is placed. The magnetic field is produced by putting an alternating current through a coil. An alternation in the back EMF (Electromotive force) occurs when the eddy current gets disturbed by a pit in the metal. This alternation is amplified so it can be seen as an image or heard as a sound by the operator.
There are lots of ways to try and prevent corrosion from occurring. One method is to uses surface treatments which protect the surface of the metal, therefore reducing the chance of corrosion and painting the metal surface can also prevent corrosion as no air or moisture can tough the metal. The use of cathodic protection can also prevent corrosion.
The use of composites within aircrafts is a relatively new concept. They were first introduced in the 1980s in secondary aircraft components, such as wing leading and trailing edges, and then as more composites were produced they made their way into larger structures in the 1990s. The Boeing 787 dreamliner tries to make the fullest use out of composite materials that is possible. Around 50% of the full aircraft, including several parts of the wings are manufactured using composites. The rest is manufactured using other materials, such as aluminium, which incorporate properties which at the present cannot be bettered by composites. At the moment composites are used mainly on non structural parts of the wings, and are used on parts such as the wings skins and the flaps.
The great attraction for airline industries to use composites within the manufacture of their aircraft is because composites can be strong, and at the same time be lightweight. This means that heavier metals can be replaced with lighter weight composites which have the same strength. This causes the overall weight of the aircraft to decrease, resulting in a more fuel efficient aircraft as less fuel is needed to be burned to move the aircraft. This is an advantage to an airline company as it would result in lower running costs for that aircraft. Costs in manufacturing were also managed to be reduced as during assembly, a smaller quantity of fasteners were needed and there were also a smaller amount of parts required to construct the component.
Composites do have disadvantages compared to metals for use within aircraft. One of these is that damage to composites can be difficult to see. Another is due to the fact that composites do not conduct electricity which may cause a problem if the aircraft is struck by lightning. These have also been concerns regarding the safety of the use of composites if there was a crash.
Make up
Composites are made up by joining together two or more materials which creates a material with improved properties compared to that of both original materials. Composites are made up of a matrix, which is a resin which joins together with a reinforcing material, which is a fibre. There are different types of reinforcing fibre and matrix which individually have different properties and need to be carefully chosen to make sure that they will be suitable for their purpose within the aircraft if chosen. The most commonly used reinforcing fibre used in aircraft is Kevlar. This is due to it having the greatest impact resistance and tensile strength compared to all other reinforcing materials while still being reasonably light.
Carbon fibre reinforced plastic is the composite used within the manufacture of the Boeing 787 aircraft wing. This composite is used as it has lightweight qualities while also being very strong, and can have the equivalent strength to steel. It is manufactured using carbon fibre as the reinforcing fibre and the matrix is usually epoxy.
One of the main disadvantages with the use of composites is the difficulty to tell if damage has occurred within it, this can be known as barely visible damage. This is due to the way in which the composite structure is manufactured and that the majority of the damage will occur behind the surface. The surface of the composite may only seem to have a small bit of damage, such as a bit of scratched paintwork, while behind it the inside of the structure has been badly damaged.
Delamination can happen due to moisture being able to go through the surface of the composite. If this moisture freezes, which can occur at high altitudes, it will start to force the layers of the composites apart. This could continue to occur if undetected causing serious damage to the composite structure. Fibre damage, where the fibres within the reinforcing material break, and matrix damage, where the matrix splits, may also occur if there is damage to the composite.
There are several ways of testing for damage to composites. The simplest one of these is tap testing. This is where the surface of the composite is tapped using either a light hammer or a coin. An area of which is undamaged will make a ringing sound where as a duller note will be heard if the area is damaged. A more accurate version of this method can be had with the use of an electronic tap tester.
Other methods of detecting damage are with the use of ultrasonic or x-ray machines. All these forms of testing are known as non destructive testing. This is due to no damage is needed to be made to the component getting tested by any of these methods.
Unlike Aluminium which can withstand damage and still be useable, composites when damaged have to be either repaired or replaced immediately. Repairing a composite panel is considerably more difficult than repairing an aluminium panel. This means that the repair will take a longer time in comparison, and will mean that the aircraft will be out of service longer. The cost of the materials to replace the damaged part is also more expensive, and may not be available at the airport where the damage is detected. Special training for working with composites may also be needed, resulting in even greater costs for the airline operator.
Lightning Strikes
The use of metal wing skins meant that if there was a lightning strike on the aircraft, it would be dispersed over the whole body of the aircraft and would dissipate at the end of the wings, through static dischargers, due to its conductive nature.
The problem with the use of some composites as a wing skin is that they are considerable less conductive compared to a metal wing skin. Therefore, this could lead to damage occurring to the composite panel as the intensity of the lightning strike would be concentrated on the spot it hit as there would be no way for the energy to disperse due to the non conductive nature of the composite. The main danger of this is that the energy of the lightning bolt may be able to penetrate through the surface of the skin enough to produce a spark inside the wings where the fuel tanks are. This spark could cause the fuel vapour within the tanks to ignite, causing an explosion within the wing.
Boeing have created several ways to prevent this scenario from occurring within their 787 dreamliner. The main method is having a thin metal mesh on the outside of the composite. This causes the composite skin panel to act in the same way as the metal one, and disperse the energy of the lightning strike over the whole surface of the aircraft. They also make sure that each fastener holding the composite skin panel to the wing structure is tightly fitting, preventing sparking from occurring between the spaces. Edge sealant will also be used to make sure there are no gaps present, and can be of either a glass fibre or goop. The use of a nitrogen generating system will be used to add nitrogen into the fuel tank, which will mix with the fuel vapours creating a safer non-flammable mixture should a spark occur.
Future Materials
New materials are continually being created by the aviation industry to try and lighten their aircrafts, and thus making them more appealing to airline operators. There has been increased competition to try and make composite materials which can be used throughout an aircraft. Other manufacturers are looking for slightly different ways to improve on materials that are available at present, with the use of shape memory alloys.
Composite Spar
The continued development of composites has lead to the creation of a material which incorporates both aluminium and composite. This material would be ideal for the use in aircraft wings due to several properties in which it possesses. The main one being that it is virtually fully resistant to metal fatigue. Metal fatigue comes about due to the cyclic loading of material. This will lead to a failure of the metal after a crack starts within the component then increases in size. This is relevant in aircraft wings as they experience cyclic loading as the lift generated by them changes during flight, such as take off and during patches of turbulence.
Compared to the manufacturing costs of composites, the manufacturing costs of this material are significantly lower. As well as this, repairs to damaged sections are more straightforward compared to composites, which reduce the cost.
The strength properties in which this material holds are greater than the composites which are used in aircraft wings at the present time. The most noticeable being the Boeing 787 which incorporates carbon fibre reinforced plastic. Due to this increased strength, the thickness of the material needed can be reduced and this can lead to a weight saving of around twenty percent, which is equivalent of between 600 to 800kg. This reduction in weight will cause a reduction in fuel use, along with the reduction in maintenance cost will reduced the overall running costs imposed on the airline operator.
Morphing wing
Shape memory alloys have existed for a reasonable long time, but it is only recently in which it has found a purpose within the airline industry. The use of shape memory alloys within the manufacture of aircraft wings is being looked at to improve the efficiency of the wing. This would happen as the flight crew would be able to change the shape of parts of the wing during different flight operations. There has been research into the development of a fully morphing wing and also that of a morphing winglet. Both of these ideas would lead to several advantages, but there are also disadvantages of the use of shape memory alloys.
The main advantage of this material is that it can remember its shape after being deformed. When the material has been deformed, if the material is then heated to a certain temperature it will return to original shape. These materials also incorporate the property of Pseudo elasticity, which is super elasticity. This is when if the alloy is subjected to load it will stretch and change form. The load imposed on the material will then be absorbed, and it will return to its original form and shape. Shape memory alloys, such as Nickel Titanium, can be polished to give very smooth finishes resulting in a reduction in drag as the air flows over it.
There are disadvantages which hold up the development of shape memory alloys, which include the difficulty and the cost of manufacture. The main problem with the use of this material in aircraft wings is that it does not have very good fatigue properties, which one needs.
A shape memory alloy is manufactured to the shape in which it will take when heat is applied to it. As the reactivity of titanium is high, the use of a vacuum during manufacture is common. Hot working is one of the methods used to create these types of alloy and is where the material is heated up to temperatures of 900oc and then shaped. Cold working is another method that can also be used, but comes with the disadvantage that the material need constant heat treatment due to work hardening occurring.
The use of this material in winglets would allow the winglets to change shape depending on the flight conditions such as the relative airspeed of the aircraft. This would allow them to have the most efficient angle between them and the wing. A reduction in wing vortices would then be able to occur over each flight operation. The drag experience on the aircraft at each point would be minimised, in turn reducing the fuel consumption of the aircraft as less thrust is required to move the aircraft would decrease. The idea of the winglets flattening out during takeoff and landing is also being examined as the wing would produce more lift at the slower speeds. This means there would be a reduction of noise generated from the engines as less thrust would be required.
Constructing a wing out of smart alloy materials has been look at as it could lead to several advantageous properties, such as weight saving and reduction in drag. This means that the wing could change shape during flight operations to make them more efficient. The wing surface would be continuous as there would be no gaps in between flap and the surface would be smoother as there would be fewer rivets needed. This would result in a reduction of drag generated from the surface of the wing. A reduction in weight could be seen from the removal of the hydraulic system needed to move the control surfaces of the wing at present. There has also been investigation into using the shape memory alloy for use in just the leading and trailing edges as a replacement for the traditional metal flaps. The overall result of using shape memory alloys to replace traditional wings would be better fuel consumption as there would be a reduction of drag and weight.
I recommend that there should be a continued development of composites within the airline sector. This will lead to the manufacture of composites which are strong enough to be used on the main structural parts of the wings, and which could also be used on other components of the aircraft. The more widely use of composites would also lead to a reduction of weight of the aircraft, making them more fuel efficient and more environmentally friendly. This would also be an advantage for the airline company as there would be a reduction in the amount of fuel needed resulting in reduced running costs.

A Business overview of Aluminium Bahrain

Culture is a term that is hard to express clearly, but people tend to sense it when they feel it. “Basically, organizational culture is the personality of the organization. Culture is comprised of the assumptions, values, norms and tangible signs (artifacts) of organization members and their behaviors. Members of an organization soon come to sense the particular culture of an organization.”  Organizational cultures are classified into seven distinct cultural dimensions that portray the company’s mission, objectives, strategies and vision. Aluminum Bahrain (Alba), one of the largest aluminum producers in the world is known for its strong organizational culture. Alba’s culture is characterized by several dimensions like people orientation, team orientation, aggressiveness, and stability. This essay will demonstrate the variety of dimensions through Alba’s momentous historical performance and inspiring vision.
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Company History
“The story of Alba marks the inception of industrial diversification in the Gulf. The company’s ongoing success as a primary producer of high-grade aluminium has brought significant economic benefits to the region and has taken the country technologically into the 21st Century. In the mid 1960s, the Bahrain Government was seeking to diversify its economic base from a heavy dependence on oil. The aim was to establish a suitable industry which would provide valuable export earnings, develop the country’s resources and create training and employment opportunities.
Bahrain was well situated geographically between the source of raw materials, particularly alumina from Australia, and the markets for primary aluminium in Asia, Europe and the Americas. Bahrain’s prime advantage was its plentiful supply of gas from the Khuff field to meet the high energy requirements of aluminium production.”  
People Orientation
Alba is known for its people oriented organizational culture. Most of the decisions and actions take into account the company’s significant stakeholders like employees, customers, suppliers and the Bahraini society.
Fostering a stable workforce through Bahrainization
Bahrainization is an important economic policy of the Government of Bahrain, and the Company has exceeded the government’s stated target levels of Bahrainization. Consequently, the Company’s permanent staff includes a high proportion of Bahraini citizens. Currently, over 87% of its permanent employees are citizens of Bahrain.
As at June 30, 2010, the Company employed 2,706 full-time equivalent employees. The following table sets forth the aggregate number of people employed by each of its departments.
Breakdown of Employees by Department
Department Bahraini Nationals Expatriates Total
Chief Executive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 13 60
Administration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 26 218
Calciner & Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455 105 560
Cast House . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 38 415
Finance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 4 25
Marketing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2 39
Metal Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 930 64 994
Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 74 254
Sourcing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 23 141
Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,357 349 2,706
Employee Benefits
Alba provides many services to employees including “comprehensive Medical Centre, subsidized canteens, an attractive savings benefit scheme, a well-equipped sports and leisure club, a unique housing scheme, transportation to work for all non-supervisory employees and a number of reward schemes including the Good Suggestion Scheme, Attendance Award and Gold Card scheme”  
Alba savings benefit scheme
The Company also operates a contributory savings scheme for its Bahraini employees, the Alba Savings and Benefit Scheme (“ASBS”). The employees’ contributions are deducted from their salaries and the Company makes an additional contribution to each employee’s savings. The scheme is established as a trust and is administered by trustees representing the employees and the Company. The trustees manage the risks relating to the scheme’s assets by approving the entities in which the scheme can invest and by setting limits for investment in individual entities. The Company’s board of directors may consider allowing Bahraini national employees to borrow from the ASBS to fund the purchase of Ordinary Shares in the Limited Offering to Bahraini citizens. “The Company’s board of directors is also considering a proposal to purchase Ordinary Shares in the Ordinary Share Offering, up to an aggregate of 3,000,000 Ordinary Shares, using its own funds, and to hold such Ordinary Shares in treasury until distribution at a future date to eligible employees.”  Under the proposed plan, each of its current employees would be granted a fixed sum of Ordinary Shares “contingent upon such employee’s continuous employment and good standing with the Company during a specified future period, and subject to certain other conditions.”  

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The Company’s personnel policy governs its relationship with its staff. The Company has invested resources to create a safe and respectful work environment that provides many different benefits to its employees, including access to on-site social and health facilities, pension plans, cultural events and subsidized meals. The Company also assists its employees with career development, further training and programs to promote home ownership.
Termination benefits
For Bahraini nationals, the Company makes contributions to the General Organisation for Social Insurance (GOSI) Scheme. “This is a funded defined contribution scheme and the Company’s contributions are charged to the income statement in the year to which it relates.”  The Company’s obligations are limited to the amounts contributed to the Scheme. The Company provides for end of service benefits “determined in accordance with the Labour Law for employees based on their salaries at the time of leaving and number of years of service.”  Provision for this unfunded commitment, which represents a defined benefit scheme, has been made by calculating the liability had all employees left at the balance sheet date.
Safety and environmental record
The Company considers health and safety concerns to be fundamentally important to its business. To this end, the Company has formulated a series of health and safety principles, policies and guidelines and established a health and safety management system. The purpose of these initiatives is to minimize any harm caused to employees in all aspects of its production activities. In addition, the Company has engaged outside consultants and auditors to assist in the development and installation of its safety policies, programs, standards, practices and procedures, and also to audit its occupational health and safety management system performance. “In May 2010, Det Norske Veritas certified that the health and safety management system of its smelter complies with Occupational Health and Safety Specification (OHSAS) 18001. The Company’s production facilities comply with the Environmental ISO 14001 standards and for the last four years, the Company has received the Gold Award from the UK-based Royal Society for the Prevention of Accidents.”  
Company’s management has long made it a priority to meet or exceed all relevant local and international safety and environmental standards as a way to demonstrate its commitment to best practices and to maintaining a long-term healthy work environment. “The Company is certified by the International Organization for Standardization. Alba’s production facilities comply with the ISO 14001 standards, and the Company is subject to various domestic environmental standards and reporting requirements established by the Bahrain Ministry of State for Municipalities and Environment, many of which are based on the environmental guidelines issued by the World Bank.”  For each of the past four years, the Company has received a “Gold Award from the UK-based Royal Society for the Prevention of Accidents for its high level of operational performance and exceptional health and safety management.”  
Current Managerial Issue
The Company’s business may be affected by shortages of skilled employees, including management teams, and labor cost inflation and increased rates of attrition; and high levels of “Bahrainization” may restrict the Company’s ability to access cheaper labor markets and introduce changes intended to optimize its labor costs
Due to the large number of smelters operating within the GCC, the Company, like all other smelters in the region, faces a shortage of skilled labor. As new smelters that have been commissioned in the region, “including Emirates Aluminium in Abu Dhabi and Qatalum in Qatar, ramp up production levels, the shortage of skilled labor could become more acute. ”  The Company might face higher than usual levels of attrition, as both new and existing smelters compete for a limited pool of skilled employees, including management teams. Such competition might also lead to higher than usual labor cost inflation, as the Company seeks to retain its skilled work force and experienced management teams.
This reputation has reinforced the Company’s long-standing commercial relationships with its customers, particularly those located in Bahrain and in fast-growing urban centers in the Kingdom of Saudi Arabia. The Company believes that it is in an advantageous position to retain its customer base within and beyond the GCC region, even in the face of increasing regional competition. Alba regularly meets its local and international customers to ascertain their requirements and accordingly alter its product mix to ensure that it meets their needs.
The Company relies on third-party suppliers of raw materials for its aluminium manufacturing. Until 2010, the Company relied on a single supplier for all of its alumina, the key raw material for the production of aluminium, but at present the Company sources it from multiple suppliers. In addition, the Company sources green petroleum coke, pitch and aluminium fluoride from suppliers in six different regions.
If there is a disruption in the supply of the Company’s raw materials, or if the Company is unable to renew any of its supply contracts, then it might have to acquire these raw materials from other suppliers or from the spot markets at less favorable prices, which could adversely affect the Company’s business, financial condition, results of operations and future prospects.
Team Orientation
Team Spirit
The newly appointed Chief Executive, Laurent Schmitt at end of his two weeks long tour around the plant was impressed by the company’s employees’ team spirit and problem solving skills to Alba’s vision. “What really impressed me was that throughout each department there is a concerted effort towards continuous improvement and operational efficiency. It is not just a matter of theory but an intrinsic part of the work culture. Everyone is involved in the decision making process, and the SMART Centres have played a key role in making this happen. They have created a sense of involvement and participation in fulfilling departmental objectives. With Alba’s 40 years of experience in the Aluminium Industry, this is a strong basement for the future improvements that Alba will have to make happen in order to consolidate its leadership position and to secure future growth opportunities.”  
Alba grasped the concept of joint consultation in Bahrain and today this technique plays a key role in the success of teamwork on the plant. “Annual programmes including granting of scholarships, the distribution of comprehensive school kits to children aged 6 – 15, a work experience programme and a Summer Camp which enables employees’ children to participate in a number of sports and leisure activities”  also support employee families.
Employees in Alba are continuously encouraged to perform at the best of their ability in order to further develop the company’s reputable accomplishments. Alba employees work aggressively and competitively contributing to the company’s achievements. The Company’s competitive strengths include its cost-effective production, large scale of production, industry experience and well-integrated operations, excellent safety and environmental record, strong reputation and integration in the fast-growing MENA region.
One of the world’s lowest-cost producers
“According to the CRU Strategies Report, the Company’s operation was in the first quartile of the aluminium cost curve in 2009.”  This means that by basing its operations in the Kingdom of Bahrain, Alba has been able to produce aluminium at lower cost than many of its competitors. The Company has access to relatively low-cost power-one of the principal inputs for aluminium production. In addition, the Company enjoys certain rights to use land owned by the Government of Bahrain at nominal fees, which further reduces its operating cost.
Producer of global and regional significance
As the fourth-largest individual aluminium smelter in the world by tonnage of capacity, Alba benefits from significant economies of scale. “For the past three years, the Company’s average annual production has exceeded 860,000 tonnes, reaching a peak of nearly 872,000 tonnes in 2008.”  .Further, the Company believes that the large scale of its operations has provided it with a stronger negotiating position in securing high-volume supply contracts for raw materials.
Extensive industry experience and well-integrated operations allowing a focus on high value-added products
The Company has a track record of nearly 40 years of production and expansion, and its experienced four-person executive management team has over 80 years of combined expertise in the metals industry. The Company has increased its production capacity through a series of expansions and upgrades.
Recent Awards and Achievements
Alba’s prominent role in the community and economy has long been recognised – a fact reflected in a number of recent awards. These include:
2001: GCC award for the best environmental activities by an industrial establishment.
2000: GCC-wide award for Bahrainisation, reflecting Alba’ s commitment to Human Resources Development.
The company also won a top supporting organisation award for HRD in this year.
2000: Environmental Management System standard ISO 14001.
2000: Millennium Business Award for Environmental Achievement. Alba was one of only 12 companies in the world to win this
prestigious award presented by the United Nations Environment Programme in conjunction with the International Chamber of Commerce.
1999: Inaugural Shaikh Khalifa bin Salman Al Khalifa Award for Excellence in Industry, presented by His Highness the Prime Minister to Alba for its outstanding contribution to the industrial development of the country and in recognition of its international success.
1998: Safety Award from the Ministry of Labour and Social Affairs. 
1998: Two Human Resources Development and Bahrainisation awards, presented by the Ministry of Labour and Social Affairs and the Bahrain Training Institute. 
1997: United Nations Environment Programme (UNEP) Environment Award presented in conjunction with the Bahrain Ministry of Housing, Municipalities and Environment.
1994: Quality Management System ISO 9002 accreditation.
1993: Bahrainisation Award from the General Committee for Bahrain Workers.
Organizational decisions and actions in Alba emphasize on maintaining the operational standards that highlight its efficient and effective performances. The strong organizational culture portrays developments and improvements that satisfy Alba’s high standards.
Continuous cost performance improvement culture
In 2009, the Company implemented a major restructuring program with a view to identifying areas for performance improvement and efficiency-related cost savings. As a part of this program, the Company focused on head-count reduction, improvement in working capital management, inventory reduction, direct sales to customers, identifying creep capacities to increase production and improving supply chain management. In order to secure the Company’s supply chain and in part as a response to the recent high volatility in raw materials pricing worldwide, the Company has prioritized efforts to improve the terms of its supply arrangements. The Company intends to further diversify its suppliers of key inputs, such as alumina, green petroleum coke and pitch, while also entering into long-term supply contracts. The Company believes that these changes would add some stability and predictability to its operations. As a part of its Operation Excellence program, the Company has streamlined some of its management and overall workforce positions.  
The Company makes regular investments in and improvements to the technology the Company uses in its administration and operations. These efforts have largely been focused on achieving additional production capacity and reaching a greater level of efficiency. The Company has a dedicated research and development team that identifies areas for potential operational improvement and presents its management with proposals for new technological or process-related modifications. Over the course of the past four decades, the Company has successfully integrated new operational technologies in the aluminium sector.
Alba Vision Study
The Company has conducted the Alba Vision study, which identified areas for future growth and expansion. The Company aims to realize performance improvements of “approximately US$100 million annually, beginning in 2010, which represents 17% of EBITDA on average for each of the past three years. The program contemplates increasing permanent performance improvements to a total of approximately US$250 million annually if the Company is able to expand its production using its creep capacity.”  
In conclusion an organization’s culture is deeply rooted within its history, values, believes and collective experiences. Like mentioned earlier it’s a difficult concept to explain but easy to feel. Alba’s strong organizational culture is demonstrated through the company’s several outstanding accomplishments. Several organizational dimensions like people orientation, team orientation, aggressiveness and stability are illustrated in Alba’s operations and future goals. It is clearly portrayed that these achievements are a result of the company’s strong organizational culture and productive employees. It is imperative that companies have a strong organizational culture; however it is impossible without hard working dedicated employees and stakeholders.