Aluminum alloy is pure aluminum with some alloying elements, such as aluminum-copper alloy, aluminum-zinc-magnesium-copper system of super-hard aluminum alloy.
Aluminum alloy has the characteristics of light weight, low cost, mechanical (uniformity of force), as well as aluminum alloy is easy to process and has a high degree of heat dissipation. Aluminum alloys are particularly suitable for use in vehicle engines.
As for the computer chassis used in most of the aluminum - copper alloy. The main consideration is heat dissipation. Because copper and aluminum mixed extrusion manufacturing out, its thermal performance is quite good, even in some high-end CPU water cooling fan is also the use of this material. If the military, the first choice is to ensure the solidity, aluminum-zinc-magnesium-copper system of super-hard aluminum alloy is the first choice.
As for whether aluminum alloy can prevent electromagnetic radiation, the answer is negative. Not to mention the process of running computers bring electromagnetic radiation, on the characteristics of the alloy itself, with a trace (not harmful to the body) radiation. Want to completely and thoroughly shield radiation non-lead can not. The density of lead is particularly high, which prevents the particles of radiation from penetrating into itself. But with lead and aluminum mixed for chassis materials and is impossible to do things, aluminum in the usual state of low hardness, and lead than aluminum is even lower, synthetic out of the chassis is simply impossible to do.
I hope my answer can bring you help!