BS 1490 · Group A · General Purpose
LM2 Aluminium Alloy
Al-Si10Cu2 — A high-silicon, copper-bearing alloy built for high-volume die casting
Nominal composition
Al-Si10Cu2
Silicon content
9.0–11.5%
Density
2.75 g/cm³
Best tensile (min)
150 N/mm²
Freezing range
580–520°C
Thermal conductivity
96 W/m·K
Hardness
70–90 HB
Overview
A high-silicon, copper-bearing alloy built for high-volume die casting
LM2 pairs roughly 10% silicon with about 1.5% copper, which is what makes it such a dependable choice for high-volume, high-pressure die casting: the silicon keeps the melt flowing into thin sections, while the copper adds as-cast strength and machinability without needing a heat-treatment step afterwards.
That same copper content is a trade-off, though — it pulls down corrosion resistance and rules the alloy out wherever decorative anodising or welding is on the cards. For general-purpose housings, brackets and covers produced at scale, LM2 remains an industry mainstay; for sand-cast work, alloys such as LM4, LM6 or LM25 are generally the better fit.
Best Suited Process
High Pressure Die Casting
LM2 is rated 3n (possible, but not the preferred choice) for sand casting under BS 1490 Table 8 — foundries typically reach for LM4, LM6 or LM25 instead. We're detailing it here for reference; if your drawing calls for LM2, talk to us about whether LM4 or LM25 would serve the part better in sand casting.
Chemical Composition
LM2 Chemical Composition — BS 1490:1988
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Silicon | Si | 9.0 | 11.5 | Main alloying element. ~10% Si gives the fluidity needed for thin-wall die casting and helps control shrinkage. |
| Copper | Cu | 0.7 | 2.5 | Boosts as-cast strength and machinability, at the cost of corrosion resistance versus lower-Cu alloys like LM25. |
| Magnesium | Mg | — | 0.30 | Impurity limit only — LM2 isn't heat-treatable, so Mg plays no strengthening role here. |
| Iron | Fe | — | 1.0 | Set higher than in LM25 — in die casting, iron helps resist die soldering. |
| Manganese | Mn | — | 0.50 | Impurity limit, controlled for melt cleanliness. |
| Nickel | Ni | — | 0.50 | Impurity limit. |
| Zinc | Zn | — | 2.0 | Impurity limit — higher Zn raises hot-cracking risk. |
| Lead | Pb | — | 0.3 | Impurity limit. |
| Tin | Sn | — | 0.2 | Impurity limit. |
| Titanium | Ti | — | 0.2 | Added as a grain refiner (typically TiB₂ master alloy). |
| Aluminium | Al | Remainder | — | Base metal. |
| Other elements | — | — | 0.05 each / 0.15 total | Each unlisted element capped individually and in total. |
Global Standards
LM2 Equivalent Grades — International Standards
BS 1490
LM2
Group A · General Purpose, Al-Si10Cu2
EN 1706
EN AC-46200
EN AC-Al Si8Cu3
ASTM / AA
383.0 / A383.0
Primary US equivalent
JIS H 5302
ADC12
Widely used Al-Si-Cu die casting alloy across Asia
DIN 1725-2
GD-AlSi9Cu3
Superseded by EN 1706
ISO 3522
Al-Si9Cu3(Fe)
ISO casting alloy designation
Mechanical Properties
LM2 Mechanical Properties — BS 1490:1988 Table 4
Minimum values from separately cast test samples. These are guaranteed minimums, not averages — properties in an actual casting vary with section thickness, cooling rate and local geometry.
| Condition | Process | Tensile N/mm² min | 0.2% Proof N/mm² | Elongation % min | Brinell HB |
|---|---|---|---|---|---|
| M | Sand / Investment | — | — | — | 70–85 |
| M | Chill / GDC | 150 | — | — | 75–90 |
| M | HPDC | ~220–240 | ~130 | <1 | 80–95 |
Physical Properties
LM2 Physical & Thermal Properties
Density
2.75 g/cm³
About a third the density of steel
Freezing range
580–520°C
Solidification temperature range
Thermal conductivity
96 W/m·K
Heat dissipation capability
Linear expansion
21 ×10⁻⁶/K
20–300°C range
Brinell hardness
70–90 HB
As-cast or stated condition
Working Properties
Corrosion, Finishing & Machining
Corrosion resistance
FairCopper content (up to 2.5%) reduces corrosion resistance — avoid for marine, food-contact or damp outdoor use without a protective coating.
Decorative anodising
PoorAnodises to a patchy grey-dark finish; not suited to decorative work.
Weldability
PoorHigh Cu content makes the alloy prone to hot cracking during welding.
Machinability
FairCopper improves chip formation compared with plain Al-Si alloys.
Casting Suitability
LM2 Casting Process Suitability — BS 1490:1988 Table 8
Scale: 4 = Excellent, 3 = Good, 2 = Fair, 1 = Poor, n = possible but not normally recommended.
3n
Sand Casting
3n
Gravity Die Casting
3n
Low Pressure Die Casting
4
High Pressure Die Casting
Heat Treatment
LM2 Heat Treatment — BS 1490:1988 Conditions
LM2 isn't heat-treated to T6 — the copper and zinc content would cause blistering under solution treatment in die-cast parts. Stress relief (TS, 200–250°C) is the only routine treatment, usually applied ahead of precision machining to settle residual casting stress.
Applications
Typical Applications of LM2
Automotive
Engine housings, transmission brackets, air intake manifolds, alternator housings, oil pump bodies
Why LM2: Thin-wall capability and dimensional accuracy at volume
Electrical
Motor frames, connector housings, enclosures, junction boxes
Why LM2: Good as-cast finish and machinability
Consumer
Door handles, window hardware, appliance components
Why LM2: Economical at high production volumes, paint-ready surface
General Engineering
Brackets, covers, frames, instrument housings
Why LM2: Consistent dimensional accuracy at volume
When Not To Specify LM2
- —Corrosion resistance matters — the copper content leaves LM2 open to galvanic corrosion; LM6 or LM25 hold up better.
- —Decorative anodising is specified — LM2 doesn't anodise cleanly.
- —T6 heat treatment is required — not applicable to this alloy.
- —The part is sand or gravity die cast — LM4, LM6 or LM25 are the better-suited choices.
- —Welding is part of the assembly — LM2 welds poorly.
Frequently Asked Questions
Common Questions About LM2
What is the chemical composition of LM2?
Per BS 1490:1988, LM2 has a nominal composition of Al-Si10Cu2 — Silicon 9.0–11.5%, Copper 0.7–2.5%, Magnesium up to 0.30%, with the balance aluminium and controlled impurity limits.
What is the European (EN 1706) equivalent of LM2?
EN AC-46200 (EN AC-Al Si8Cu3), which supersedes the older German DIN designation GD-AlSi9Cu3.
What is the ASTM equivalent of LM2?
383.0 / A383.0 is the primary US equivalent.
Can LM2 be heat treated to T6?
No — only stress relief (TS) is routinely applied; the alloy isn't taken to a T6 condition.
Which casting processes suit LM2?
Per BS 1490 Table 8: Sand casting and Gravity Die Casting are rated 3n (possible but not the preferred route), Low Pressure Die Casting 3n, and High Pressure Die Casting 4 (Excellent) — LM2 is fundamentally a die-casting alloy.
What is the density of LM2?
2.75 g/cm³ — roughly a third the density of steel, useful wherever weight saving matters.
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