Please dont try to weld aluminum to steel. Non ferrous materials wont weld to ferrous materials under any of our circumstances. Also, although some will layer some nickle in their steel for looks, it reduces the durablity of the edge, because it wont harden. I use all carbon steel in mine. 1084 and 15N20 works well.
For welding damascus, please do some reading and find someone to watch it done too. It's not something you want to try cold turkey. Lin
Edited to add:
After reading what I said, I may have sounded a little bossy. I dont mean to be at all. I really want your first attemp to be successful.