I personally have no idea what kinds of alloys were used in the aluminum racquets I've had experience with over the years. All I know is unless you are somewhat careful they all end up getting pretty beat up in a way that seems worse than graphite. Of course any racquet can be destroyed if abused but graphite seems to wear away a bit more gracefully.
Given how cheap you can get a basic graphite frame, I'm not sure there is any reason to buy aluminum frames any more. And of course my advice to almost anyone who wants a good frame these days is to look for something used in good condition. You can save a lot of money that way.