Aluminum-Silicon Eutectic Modification

The chemical alteration of eutectic silicon in casting alloys through small additions of sodium or strontium, converting needle-like structures into globular forms. This improves the ductility of the casting.

When welding modified cast aluminum, you have to be careful: The modification with sodium or strontium, which finely distributes the silicon, burns out quickly in the heat-affected zone. This can make the structure coarse and needle-like again, increasing the risk of hot cracking. Keep the heat input as low as possible and let the part cool slowly and evenly. If you stir the melt too much or get too hot, the structure will flip. When in doubt, mechanically remove the joint area before welding and clean it well.

MetallurgieSchweißtechnik