I've never tried it, but there are pros and cons when compared with copper. Aluminum has a lower melting point, but it has less of a chance of setting up a corrosion cell. Try it, I think it should work. For that matter, you could probably also use tin, lead, or any other soft metal that won't melt in the application.
Since many cylinder heads are aluminum, I don't see why an appropriate aluminum exhaust gasket wouldn't work.
Copper is often mentioned as a great exhaust gasket, but there can be electrolysis with aluminum and copper if there is moisture present.
Just ask my old biology teacher who hand made an aluminum canoe with pretty brass rivets.