LM25 (BS 1490) and A356 (Aluminum Association) are closely related aluminium casting alloys with about 6.5-7.5% silicon and a small magnesium addition. The magnesium allows heat treatment, most commonly to the T6 condition, which gives a good balance of strength and elongation. The European equivalent family is AlSi7Mg. A356 has tighter iron limits, and A356.2 is a high-purity ingot grade.
Why it matters when buying
- Iron is the critical impurity: higher Fe forms brittle needles that cut ductility, so check it closely on the spectro report.
- Magnesium range decides the response to T6 heat treatment; confirm it is inside the specified band.
- Many users want the ingot pre-treated with titanium-boron grain refiner and strontium modifier, or will add them at the foundry.
- Primary-based A356 usually costs more than scrap-based LM25; match the grade to your quality requirement.
Typical uses
Car and two-wheeler alloy wheels, suspension and chassis parts, aerospace and defence castings, pump and valve bodies, and structural gravity or low-pressure castings. Compare with LM6 for non-heat-treated parts. Listings are under alloy ingots.