That's a tough little weld!
There are a lot of things you need to do just right to get those to pass.
It really can make you skeptical when under ideal test conditions you see problems.
There were a lot of similarities in profile and porosity in those slides.
The arc length needs to be ultra-tight, which is very hard to do with aluminum as it tends to "puff" when filler is added.... The operator needs to gently lift the tungsten every time he dips, and then lower it back down in a rhythm... Also with a very minimal push angle is necessary, if you push more than about 10 degrees you see this kind of result.
