Aluminum-Silicon Eutectic
A specific mixture ratio structure in foundry alloys that solidifies at a constant, minimal melting temperature. It imparts excellent castability and low shrinkage to the cast material.
The aluminum-silicon eutectic is basically the trick with casting alloys: with the right mixture, the whole structure melts at a constant temperature and not over a range. This makes the material nice and fluid when casting, and shrinkage during cooling remains low. That's why you can also get complicated, thin-walled castings done cleanly with it. When welding such a casting, you have to be careful: the alloy is sensitive if you heat it too much. Then the structure tips over and hot cracks can occur. So keep the heat input low and work quickly, instead of heating the spot for a long time. A clean, calm weld pool is more important than anything else.