Aluminium
Aluminium is the most abundant metal on earth. It is light, ductile, easily worked, has good electrical and thermal properties, and is corrosion resistant. The strength of aluminium is low in comparison with steel but can be greatly increased by alloying plus cold working or heat treatment. Thus aluminium alloys become extremely attractive engineering materials, finding wide uses in the vehicle, aeronautical, marine, electrical and food packaging industries. Aluminium alloys may be sub-divided into two main groups, cast alloys, and wrought alloys. Wrought alloys are further sub-divided into heat-treatable and non-heat-treatable alloys. Casting alloys may be based on aluminium-silicon, aluminium-copper or aluminium-magnesium compositions. Heat-treatable wrought alloys include aluminium-copper (2xxx series), aluminium-silicon-magnesium (6xxx series) and aluminium-zinc-magnesium (7xxx series). These alloy grades can develop high strength by solution treatment followed by ageing at elevated temperature. Non-heat-treatable wrought alloys include pure aluminium (1xxx series), aluminium-manganese (3xxx series) and aluminium-magnesium (5xxx series). They can be strengthened only by cold work. Wrought aluminium-silicon alloys (4xxx series) are supplied only as wire. MIG and TIG welding are the most common welding processes used and many of the alloys are readily welded. However, the 2xxx series are virtually unweldable and the other heat-treatable alloys are crack sensitive. Plasma and laser are the most common cutting processes used.
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