[mech engineer hat=on]
Normalization is a proper term for heat stress relieving.
It is not a stretch to say that all of the experimental tube airframes are mig welded. (ie: Kitfox, Avid, Just, etc, etc.) Low carbon wire is usually used. This could be the reason it's not used in certified planes.
I don't know why mig welding would cause magnetic problems and tig would not. Both use an electric arc to induce heat.
Kitfox IV - 1050, 912UL - Flyer
Kitfox IV - 1200, 912UL - Project
I'd rather die trying to live,
Than live trying not to die.