Gas welding aluminium(NOT F^#KING ALLOY) is pretty simple, just apply flux to the filler rod when the pool forms throw the filler at it. After you have completed the weld then your problems begin.As that flux you lavished on the job is highly corrosive, the job will have to be washed, boiled and neutralised and do the same all over again.Aluminium can also be brazed with the correct flux and a 4043 filler wire. Beware as the melting point of the flux and the aluminium is very close.
With that out of the way we can move to Tungsten Inert Gas, you have DC and AC, DC is for ferrous metals/alloys and AC is for non-ferrous mostly aluminium and magnesium(could there be another??). Next is the machine, modern power sources have all the parameters of the arc controllable.Slope up Slope down, Pulse, Pre/Post Flow,Crater Fill,High Frequency start AC Balance and Frequency. So it's possible to have your weld infintiely varied. From a thin narrow weld that goes deep into thick material or a wide shallow weld on very thin material (like 0.5mm Al).Also modern power sources have a square wave (as opposed to an old sine wave) on AC this give more time at peak amps and less time at near zero amps.The arc is controlled by HF start (bringing the torch in close contact with the job) or lift arc,when the electrode is lifted off the job the arc starts.Then there is a botton on the torch to press once to start then again to begin slope down amps/crater fill or that can be done with a foot control.
A power source is very cheap these days for a single phase, something I couldn't do without.
So bit more to it than the old oxy.