You can weld aluminum with a Oxy-Acetylene torch...

Many years ago (like 50) when i learned that those beautiful aluminum fuel tankers were all torch welded, I just had to learn how to do it... and I made a lot of motorcycle parts after that.
Many custom aluminum car bodies were all torch welded it takes flux a razor sharp eye and a steady hand. The fact that aluminum doesn't change color before the puddle drops into the hole can be disheartening.