Aluminum-Scandium Grain Refinement

Scandium is an addition that ensures fine grain in aluminum alloys. The fine grain gives the material more strength and makes it less prone to cracking. When welding, you have to be careful not to overheat the alloy or leave it in the heat zone too long. If you coarsen the structure too much, you lose the benefits of scandium again. So keep the heat input as low as possible and don't let the weld cool unnecessarily slowly, then the structure stays nice and fine and stable.