LM25 is an aluminium-silicon-magnesium casting alloy with about 7% silicon. It casts well in sand and gravity die moulds, resists corrosion and, unlike LM6, can be heat treated for higher strength. It is widely used for automotive, pump, motor and marine castings.
Quick facts
- Type
- Al-Si-Mg casting alloy, heat treatable
- Silicon
- About 6.5–7.5%
- Tensile strength
- About 160 MPa as cast; about 230–280 MPa fully heat treated (TF)
- Casting
- Sand, gravity die and low-pressure die casting
- Corrosion resistance
- Very good, including in marine air
- Close equivalents
- A356, AlSi7Mg (EN AC-42000 family)
Tempers
| Condition | Meaning | Use |
|---|---|---|
| M | As cast | General castings |
| TE | Precipitation treated | Moderate strength, stable size |
| TB7 | Solution treated and stabilised | Better ductility |
| TF | Fully heat treated | Highest strength |
Typical chemical composition
| Element | % |
|---|---|
| Silicon (Si) | About 6.5–7.5 |
| Magnesium (Mg) | About 0.20–0.60 |
| Iron (Fe) | Up to about 0.5 |
| Copper (Cu) | Up to about 0.2 |
Values are typical. The exact limits depend on the standard and supplier; ask for the mill test certificate when it matters.
Typical uses
- Alloy wheels and automotive brackets
- Pump bodies and impellers
- Motor housings and end covers
- Marine and food-handling castings
- Pressure-tight and structural castings
Need parts made in LM25 aluminium casting alloy?
Post your requirement free. Workshops that take your kind of work see it and get in touch. You only talk to the ones that fit.
Get startedRelated
Related job work
Questions
- What is the difference between LM6 and LM25?
- LM6 has about 12% silicon and flows very well for thin, complex castings but cannot be heat treated. LM25 has about 7% silicon plus magnesium, so it can be heat treated for much higher strength.
- Is LM25 the same as A356?
- They are close equivalents: both are Al-Si7-Mg alloys. Check the exact limits if a drawing names one specifically.
- Can LM25 be welded?
- Yes, castings in LM25 can be TIG welded for repairs, though heat-treated strength drops near the weld unless the part is heat treated again.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 15 October 2026.