Casting Alloys
Low melting point AlX eutectics are ideal for casting
- X can be Cu, Mg or Si additions up to 12wt%
- Often designated by LM (Light metal)
Al-Si eutectic occurs at 11% Si
- Unmodified alloys have coarse needles of Si in Al with low strength and ductility
- Add 0.01% sodium as a refiner to get fine Si precipitates in Al - good strength and ductility
Casting alloys can be used as cast (e.g. LM6) or heat-treated to increase strength (LM25)