Cast Aluminium

Aluminium is very well available in the form of bauxite. The reason for its high price is  the large amount of electric energy, necessary for the extraction process: 148 MJ/kg Al. Recycling of  used material (secondary Al) takes considerably less energy: 10 MJ/kg Al. Therefore recycling is favourable, although some alloying elements cause problems. Cast Al alloys represent about 15% of Al applications. Compared to steel, both density and Young's modulus of Al are a factor 3 lower. Strength is comparable to plain carbon steels. Corrosion resistance is good, especially for pure Al and Al-Mg alloys, as a result of a closed protective oxide layer. Castability (and weldability) of Al are good, due to the low melting temperatures caused by the alloying elements. Cast alloys generally contain a higher percentage of alloying elements compared to wrought alloys. Manufacturing of Al by machining is difficult because of the high plasticity.