Aluminum Casting Alloy Modification
Chemical melt treatment of hypoeutectic AlSi alloys, typically using sodium or strontium, to achieve a finely dispersed morphology of the silicon eutectic and enhance elongation.
Modifying aluminum casting alloys is done to transform the brittle, needle-shaped silicon in the structure into fine, round grains. You do this by adding a so-called modifier such as sodium or strontium to the melt before casting. This makes the material significantly tougher and more formable. If you want to weld such a modified part, you have to be careful: the welding heat causes the fine structure in the weld area to be lost again, the silicon coarsens again, and the weld can become brittle. For welding itself, this means: use a suitable filler material and consider whether you need to treat the weld afterwards if requirements are high. The exact amount of modifier and melt handling are crucial in the foundry process – you must follow the manufacturer's specifications.