Aluminum-Magnesium Solid Solution Hardening

Magnesium is a solid-solution former in Aluminum and gives a noticeable increase in strength. When welding AlMg alloys, that means: you get a material that's easy to work with, but you have to be careful not to put in too much heat. If you make the weld too hot or stay on it too long, the structure can coarsen and the weld loses toughness. So keep the heat input as low as possible and don't let the weld cool too slowly, then the structure stays fine and the weld is less prone to cracking.