Aluminum tube welding repair is really only practical on 7005 or other "naturally aged" alu metallurgy. Majority of commercial aluminum frames use 6061-T6 with T6 heat treating needed to restore strength after welding. Big manufactures can efficiently perform the post-construction heat treating in large ovens with batches of frames held in jigs to prevent warpage but attempting to DIY or pay for a single frame to get heat treated is really not practical for a repair.