| Aluminium By Sam Davyson | ||
| Home | . | |
| Abundance | . | |
| Uses | . | |
| History | . | |
| Weaknesses | . | |
| Structure | . | |
| Extraction | . | |
| Alloys | . | |
| Conductivity | . | |
| Corrosion | ||
| Properties | . | |
| Questions | . | |
| Bibliography | . | |
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Youngs Modulus: 70 GPa (in alloys)
This is a measure of elasticity, or how easily something with stretch. It is found by dividing stress by strain. Where stress is the load applied to the material divided by the cross sectional area of the material, and where strain in the increase in length over the original length (so percentage increase of length). As stress is measured in Pascals (or force per unit area) and strain is imply a ratio without units the Youngs modulus is also measured in Pa. Aluminium's Youngs modulus is quite low, and elements like Iron for example have much higher values such as 211 GPa. Aluminium's alloys in general have higher modulus's of elasticity due to pinned dislocations in their structure.
These are also a property relating to how easily deformation occurs. Aluminium is both very malleable, and very ductile. In fact aluminium is the 2nd most malleable metal, and the 6th most ductile, both of these are very important for its uses. Malleability is the property of a metal to be deformed by compression without cracking or rupturing, and ductility is the ability to deform plastically without fracture under tensile force. In a practical sense if a material is malleable it means that it is possible to roll it into sheets, and if it is ductile it can be drawn into wires. Aluminium can do both like most metals can. The structure of metals as positive ions in a "sea" of negative electrons means that the positions of the ions are not as fixed as one may first imagine, and as the ions are just held in place by attraction they can slide past each other giving metals malleability and ductility.
Hardness: 420 MPa
Hardness is the ability to not be easily scratched, in is measured in Pascals or force per unit area. Aluminium's hardness is relatively low due to its low density (see below). This means that it is easier to scratch than other metals like steel are.
This gives aluminium its unique lightweight property and extends the uses of aluminium vastly. Really this is the key property that sets aluminium apart from so many other metallic elements. Transport vessels made of aluminium can carry more cargo with the same amount of fuel than vessels made of other materials as the aluminium itself it so much lighter. Why does it have such a low density? Because of the number of protons and neutrons (which make up almost all of an atoms weight) in the nucleus. Aluminium has a mass of just 27, which is very low compared to most other metals.
Melting Point: 660.32 °C Boiling Point: 2519 °C
These relatively low thermal points help aluminium to be reshaped, and welding quite easily. For a metal a melting point of 660.32 °C is very low.
Aluminium has a very low electrical resistivity, and therefore a high electrical conductivity. This is measured in Ohms meters, as resistivity is equal to the resistance of a certain sized piece of the material multiplied by the area and divided by the length. This gives a standard measure for a material that can be used easily in comparison. In relation to other metals aluminium has quite a low resistivity, it is not the best conductor, but it is by no means the worst. Aluminium is also a very good thermal conductor as is discussed in conductivity.
Reflectivity: High 71% unpolished and when polished: 97%
Aluminium is extremely reflective, when polished (some sources say) it is the most reflective material, for this reason it is now frequently used in lights. It is also very heat reflective and because of this people use it in their car windscreens to reflect the heat, and to keep the car cool on sunny days.
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