16ga 6061 aluminum using 1/16" (1.6mm) 4043 filler.
I used a tapered 2% lanthanated 3/32" (2.4mm) tungsten.
Welding small aluminum coupons with a chill backing,
This can also be done without backing but on small pieces of aluminum heat can saturate the piece and the puddle gets very watery.
Chill bars are not usually required on larger pieces