I am afraid that's there's no such thing as aluminium strings.
You might want to check out the Titaniums fron Ernie Ball and I've heard really good things about the
Rohrbacher Titanium strings too.
Assuming yours is an acoustic, the majority of strings are made out of various combinations of copper, phosphor bronze and tin.
Why so? Because I assume that during the formative years of the modern acoustic guitar, they tried all sorts of materials and decided that the mentioned materials sounded the best.
Aluminium strings, well, to be honest, I'm not sure if I'd like its tone.
Secondly, aluminium is expensive. I'm don't think I want to pay like $30 for a pack of uncoated aluminium strings.
What you're probably looking for are coated strings.
The string-market is mainly divided into coated and non-coated strings. Coated strings cost a bit more but can last you a whole lot longer due to their special coating (method of coating differs from brand to brand).
Un-coated strings are just your normal strings.
For coated strings, check out the usual suspects of Elixirs, Cleartones, Wyres, D'addarios EXP etc, the list goes on.