Switch to 2.4mm tungsten.
Standard 5 cup.
Looks like you’ve got too much stickout causing the tungsten to discolour. Bring the tungsten in and lower argon flow. 10lpm is high for aluminium.
Not knowingly welded 5754 before, I’m in a position of having to choose a filler rod. Materials welded are:
5754 to itself
5754 to 6082
5754 to 6063
6063 to 6082
All on the same part. The part is an engine coolant header tank so will see a sustained elevated temperature.
Going off the...
Poor fit up. Don’t have material hanging over the edge it actually makes it worse.
Open corner joint with perfect fit up and you could fuse it no problem.
We’ve always fitted foam afterwards. The foam doesn’t have to be in one whole piece you can cut it in chunks to fit in the cell. Also cut to fit around collectors and baffles etc.