BS 1490 · Group A · General Purpose
lm2
Aluminium Alloy
Al-Si10Cu2 — The Primary High-Pressure Die Casting Alloy
Sand Casting
Gravity Die Casting
Low Pressure Die Casting
High Pressure Die Casting
ISO 9001:2015
At a Glance
- Nominal composition
- Si content
- Density
- Best tensile (min)
- Freezing range
- Thermal conductivity
- Hardness
- Al-Si10Cu2
- 9.0–11.5 %
- 2.75 g/cm³
- 150 N/mm²
- 580–520 °C
- 96 W/m·K
- 70–90 HB
Overview
The Primary High-Pressure Die Casting Alloy
LM2 is the most widely used aluminium die casting alloy in the BS 1490 series for high-pressure die casting (HPDC). Its Al-Si10Cu2 composition delivers excellent fluidity, strong hot-tear resistance, and consistent dimensional accuracy in high-volume production. The combination of ~10% silicon and ~1.5% copper gives reliable castability and good as-cast mechanical properties without the need for heat treatment.
While LM2 is rated 3n (possible but not normally recommended) for sand and gravity die casting, it is the definitive HPDC alloy — rated 4 (Excellent) for pressure die casting. Its higher iron and copper content compared to LM25 means it is not specified where corrosion resistance or decorative anodising are required, but for general engineering housings, brackets, and covers at high volumes, LM2 remains the industry standard.
HPDC Specialist — Not Normally Used in GDC
LM2 is rated 3n for both sand casting and gravity die casting in BS 1490 Table 8 — the alloy can be cast by these processes but alternative alloys (LM4, LM25, LM6) are preferred. LM2 is optimised for high-pressure die casting where its higher Fe content reduces die soldering and its Cu content improves as-cast strength and machinability.
Chemical Composition
LM2 Chemical Composition — BS 1490:1988
| Element | Symbol | Min % | Max % | Role in alloy |
|---|---|---|---|---|
| Silicon | Si | 9.0 | 11.5 | Primary alloying element. ~10% Si gives excellent fluidity for thin-wall HPDC. Reduces shrinkage and provides good pressure tightness. |
| Copper | Cu | 0.7 | 2.5 | Improves as-cast strength and machinability. Higher Cu range than LM25 — note this reduces corrosion resistance significantly. |
| Magnesium | Mg | — | 0.30 | Impurity limit. LM2 is not heat-treatable; Mg serves no precipitation-hardening function here. |
| Iron | Fe | — | 1.0 | Higher Fe limit (1.0%) than LM25 (0.5%). In HPDC, Fe reduces die soldering. Essential for HPDC tooling life. |
| Manganese | Mn | — | 0.50 | Impurity limit. Controlled to maintain clean melt. |
| Nickel | Ni | — | 0.50 | Impurity limit. |
| Zinc | Zn | — | 2.0 | Impurity limit. Higher Zn increases hot-cracking risk. |
| Lead | Pb | — | 0.3 | Impurity limit. |
| Tin | Sn | — | 0.2 | Impurity limit. |
| Titanium | Ti | — | 0.2 | Grain refiner when added as TiB₂ master alloy. |
| Aluminium | Al | Remainder | Base metal. Composition verified by OES (ARUN Technology UK, MERLIN-4 ULTRA). | |
| Other elements | — | — | 0.05 each / 0.15 total | Each unspecified element ≤0.05%, total ≤0.15%. |
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
383.0 is the primary US equivalent
JIS H 5302
ADC12
Al-Si-Cu die casting alloy — widely used in 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 per BS 1490:1988. These are guaranteed minimums — not average values. Properties in actual castings 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
Approx. 1/3 the density of steel
Freezing Range
580–520 °C
Solidification temperature range
Thermal Conductivity
96 W/m·K
Heat dissipation capability
Electrical Conductivity
— % IACS
Relative to copper standard
Linear Expansion
21 ×10⁻⁶/K
20–300°C range
Brinell Hardness
70–90 HB
As-cast or stated condition
| Property | Rating | Notes |
|---|---|---|
| Corrosion resistance | Fair (D) | Cu content (up to 2.5%) significantly reduces corrosion resistance. Not suitable for marine, food processing, or wet outdoor environments without protective coating. |
| Decorative anodising | Poor (D) | Anodises poorly — grey/dark patchy appearance. Not suitable for decorative anodising. |
| Weldability | Poor | High Cu content causes hot cracking during welding. Not recommended for welded assemblies. |
| Machinability group | 2 — Fair | Group 3 machinability. Cu improves chip formation vs pure Al-Si. |
Casting Suitability
LM2 Casting Process Suitability — BS 1490:1988 Table 8
Ratings from BS 1490:1988 Table 8. Scale: 4 = Excellent, 3 = Good, 2 = Fair, 1 = Poor, n = Not normally recommended.
Sand Casting
3n
Gravity Die Casting (GDC)
3n
Low Pressure (LPDC)
3n
High Pressure (HPDC)
4
| Castability Property | Rating | Explanation |
|---|---|---|
| Fluidity | 3 – Good | Good fluidity from high Si content. Suitable for thin-wall HPDC. |
| Resistance to hot tearing | 4 – Excellent | Excellent resistance to hot tearing during solidification. |
| Pressure tightness | 4 – Excellent | Good pressure tightness achievable in HPDC with correct process control. |
| Machinability (as-cast) | 2 – Fair | Group 3 machinability. Cu improves chip formation vs pure Al-Si. |
Heat Treatment
LM2 Heat Treatment —BS 1490:1988 Conditions
M
As Cast
No heat treatment. Used as-cast. Dimensional stability is the priority.
TS
Stress Relieved
200–250°C, 2–4 hours. Reduces residual casting stresses without significant property change.
TB
Solution + Natural Age
Solution treat, quench, age at room temperature. Strength develops over days to weeks.
TB7
Solution + Stabilise
Solution treat, quench, then stabilise at low temperature. Good ductility and dimensional stability.
TE
Artificially Aged Only
Age at 160–180°C, 6–12 hours. Moderate strength improvement without solution treatment.
TF
T6 — Peak Strength
Solution treat + quench + artificial age. Peak strength condition. Full in-house at Creative Alucast.
TF7
T7 — Over-aged / Stabilised
Solution treat + quench + over-age. Slightly lower strength than TF but superior dimensional stability.
Heat Treatment — As-Cast Only
LM2 is not heat-treatable to T6. The Cu and Zn content means solution treatment would cause blistering in HPDC castings. Only stress relief (TS) at 200–250°C is applicable, primarily for dimensional stability before precision machining.
Applications
Typical Applications of LM2
| Industry | Typical Parts | Why LM2 |
|---|---|---|
| Automotive | Engine housings, transmission brackets, air intake manifolds, alternator housings, oil pump bodies | Thin-wall capability, dimensional accuracy, high-volume economy |
| Electrical | Motor frames, connector housings, enclosures, junction boxes | Good as-cast surface finish, EMI shielding, machinable |
| Consumer | Door handles, window hardware, appliance components | High-volume HPDC economy, good surface for painting |
| General Engineering | Brackets, covers, frames, instrument housings | Consistent dimensional accuracy at high volumes |
Engine Housings
Transmission Brackets
Alternator Housings
Motor Frames
Appliance Parts
Instrument Housings
Junction Boxes
Oil Pump Bodies
Connector Housings
Door Hardware
When NOT to Specify LM2
Do not specify LM2 when: (1) corrosion resistance is required — Cu content makes LM2 susceptible to galvanic corrosion; use LM6 or LM25 instead; (2) anodising is specified — LM2 anodises poorly; (3) T6 heat treatment is required — not applicable; (4) the casting will be sand or gravity die cast — use LM4, LM6, or LM25; (5) the part requires welding — LM2 is poorly weldable.
Frequently Asked Questions
Common Questions About LM2
What is the chemical composition of LM2 aluminium alloy?
LM2 per BS 1490:1988 has nominal composition Al-Si10Cu2. Silicon: 9.0–11.5%, Copper: 0.7–2.5%, Magnesium: —–0.30%. The remainder is aluminium with controlled impurity limits.
What is the EN 1706 / European equivalent of LM2?
The EN 1706 equivalent of BS 1490 LM2 is EN AC-46200, with chemical symbol designation EN AC-Al Si8Cu3. This European standard supersedes the German DIN designation GD-AlSi9Cu3.
What is the ASTM / AA equivalent of LM2?
The ASTM/Aluminium Association equivalent of LM2 is 383.0 / A383.0. 383.0 is the primary US equivalent.
What is the JIS equivalent of LM2?
The JIS H 5302 equivalent of LM2 is ADC12. Al-Si-Cu die casting alloy — widely used in Asia.
What is the tensile strength of LM2?
The minimum tensile strength of LM2 is 150 N/mm² in the best condition and process per BS 1490:1988 Table 4 (separately cast test samples). Properties vary with casting process and heat treatment condition.
Can LM2 be heat treated to T6?
No — LM2 is not normally heat-treated to T6. Available conditions: M, TS.
What casting processes are suitable for LM2?
Per BS 1490:1988 Table 8: Sand casting (3n), Gravity Die Casting (3n), Low Pressure Die Casting (3n), High Pressure Die Casting (4). Scale: 4=Excellent, 3=Good, 2=Fair, n=Not recommended.
What is the density of LM2 aluminium alloy?
The density of LM2 is 2.75 g/cm³ — approximately one-third the density of steel (7.85 g/cm³), making it ideal for lightweight structural applications.