Is the IP5 an aluminium alloy? I know its anodized but I was just assuming that the base material is pure aluminium.
Dunno about the iPhone 5 per se and I'm not an expert, and furthermore, Apple hasn't released the specifics about the alloy used. However, a few out there in internetland who work with aluminum believe it's some form of
6061 aluminum that's used in the MacBook Pro. Why 6061? It's torsionally pretty strong without being too brittle, it's not overly expensive, it's widely available, and it's decent to work with. I do know that lots of bikes are made with 6061, although weldability is a characteristic that's valued there, and weldability is irrelevant for the MacBook Pro. However, that 6061 guess is just the opinion from a few people out there who post in forums. I don't know if that's true or not, or if it's some other kind of aluminum alloy.
No, it's not as if it's like it's some sort of high-dollar metal alloy, but those using the "it's not premium metal" argument are completely missing the point. The point is that it's got some significant advantages over plastic. But like I said before, just because it's aluminum doesn't automagically make it special. You can make crap out of aluminum, too.
I'm not too keen on the anodization though. Even well-anodized aluminum
will eventually show the wear. OTOH, non-anodized aluminum will simply show scratches, which is a lot easier to tolerate than scratched anodized surfaces where the aluminum shows through. It looks horrible if there are a lot of such scratches on a black anodized surface.