BS 1490 · Group B · Special Purpose
lm9
Aluminium Alloy
Al-Si12Mg0.5Mn0.5 — The Premier Alloy for Low Pressure Die Casting
Sand Casting
Gravity Die Casting
Low Pressure Die Casting
T6 Heat-Treatable
ISO 9001:2015
At a Glance
- Nominal composition
- Si content
- Density
- Best tensile (min)
- Freezing range
- Thermal conductivity
- Hardness
- Al-Si12Mg0.5Mn0.5
- 10.0–13.0 %
- 2.68 g/cm³
- 295 N/mm²
- 575–555 °C
- 150 W/m·K
- 65–75 HB
Overview
The Premier Alloy for Low Pressure Die Casting
LM9 combines the outstanding castability of a eutectic Al-Si alloy (10–13% Si) with the heat-treatability of Mg-containing alloys (0.2–0.6% Mg). This unique combination makes it the premier alloy for low pressure die casting — rated 4 (Excellent) for LPDC in BS 1490 Table 8, the highest rating of any alloy for that process. The addition of 0.3–0.7% manganese improves strength at elevated temperatures.
LM9 delivers the fluidity and hot-tear resistance of LM6 combined with the T6 precipitation-hardening response of LM25. In the TF (T6) condition from chill casting, LM9 achieves a minimum tensile strength of 295 N/mm² — the highest T6 strength of any standard LM-series alloy in GDC. It is not recommended for HPDC.
Rated 4 (Excellent) for LPDC — Best in Series
BS 1490 Table 8 rates LM9 as 4 (Excellent) for low pressure die casting — the highest possible rating. Combined with T6 heat treatability delivering 295 N/mm² minimum tensile in chill cast condition, LM9 is the specification of choice for safety-critical LPDC components: wheel hubs, cylinder heads, structural brackets.
Chemical Composition
LM9 Chemical Composition — BS 1490:1988
| Element | Symbol | Min % | Max % | Role in alloy |
|---|---|---|---|---|
| Silicon | Si | 10.0 | 13.0 | 10–13% Si — eutectic or near-eutectic composition giving excellent fluidity and hot-tear resistance. Same Si range as LM6, but LM9 adds Mg for heat-treatability. |
| Copper | Cu | — | 0.20 | Strict limit ≤0.20%. Low Cu preserves corrosion resistance and ensures clean T6 heat treatment response. |
| Magnesium | Mg | 0.2 | 0.6 | 0.2–0.6% Mg forms Mg₂Si precipitates during T6 ageing — same mechanism as LM25. For T6 applications, Mg should be near the upper limit (0.45–0.60%). Critical alloying element. |
| Iron | Fe | — | 0.6 | Controlled to ≤0.6%. Low Fe limit — LM9 is intended for GDC and LPDC where ductility matters. Fe forms β-AlFeSi platelets that reduce elongation if unchecked. |
| Manganese | Mn | 0.3 | 0.7 | Impurity limit. Controlled to maintain clean melt. |
| Nickel | Ni | — | 0.1 | Impurity limit. |
| Zinc | Zn | — | 0.1 | Impurity limit. Higher Zn increases hot-cracking risk. |
| Lead | Pb | — | 0.1 | Impurity limit. |
| Tin | Sn | — | 0.05 | 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
LM9 Equivalent Grades — International Standards
BS 1490
LM9
Group B · Special Purpose Al-Si12Mg0.5Mn0.5
EN 1706
EN AC-43300
EN AC-Al Si9Mg
ASTM / AA
A360.0
Al-Si9Mg — primary US equivalent
JIS H 5302
ADC3
Al-Si-Mg die casting alloy
DIN 1725-2
GD-AlSi10Mg
Superseded by EN 1706
ISO 3522
Al-Si10Mg
ISO casting alloy designation
Mechanical Properties
LM9 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 | Chill / GDC | 190 | — | 3 | 65–75 |
| TE | Sand / Investment | — | — | — | 80–90 |
| TE | Chill / GDC | 230 | — | 2 | 85–95 |
| TF | Sand / Investment | 240 | — | — | 90–100 |
| TF | Chill / GDC | 295 | — | — | 100–115 |
Physical Properties
LM9 Physical & Thermal Properties
Density
2.68 g/cm³
Approx. 1/3 the density of steel
Freezing Range
575–555 °C
Solidification temperature range
Thermal Conductivity
150 W/m·K
Heat dissipation capability
Electrical Conductivity
38 % IACS
Relative to copper standard
Linear Expansion
21 ×10⁻⁶/K
20–300°C range
Brinell Hardness
65–75 HB
As-cast or stated condition
| Property | Rating | Notes |
|---|---|---|
| Corrosion resistance | Good (B) | Low Cu (≤0.20%) gives good corrosion resistance — better than Cu-bearing alloys. Suitable for most non-marine environments. |
| Decorative anodising | Fair (E) | High Si gives dark grey anodised appearance. Protective anodising applicable. Not for decorative use. |
| Weldability | Good | Weldable. Low Cu content prevents hot cracking. Post-weld T6 restores strength. |
| Machinability group | 2 — Fair | Group 2 machinability. High Si causes some tool wear. Better than LM6 but below Cu-bearing alloys. |
Casting Suitability
LM9 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
3
Gravity Die Casting (GDC)
3
Low Pressure (LPDC)
4
High Pressure (HPDC)
n
| Castability Property | Rating | Explanation |
|---|---|---|
| Fluidity | 3 — Good | Eutectic Si range gives good fluidity. LPDC controlled fill maximises the benefit of LM9's fluidity. |
| Resistance to hot tearing | 4 — Excellent | Eutectic composition gives excellent hot-tear resistance, matching LM6. |
| Pressure tightness | 4 — Excellent | Excellent pressure tightness — ideal for hydraulic and pressure-tight LPDC components. |
| Machinability (as-cast) | 2 — Fair | Group 2 machinability. High Si causes some tool wear. Better than LM6 but below Cu-bearing alloys. |
Heat Treatment
LM9 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.
Full T6 Heat Treatment — In-House at Creative Alucast
LM9 responds fully to T6 heat treatment (TF condition). Solution treat at 515–525°C, quench, artificially age at 160–175°C. Delivers 295 N/mm² minimum tensile in chill/GDC — the highest T6 tensile of any standard LM alloy. T6 is not applicable to HPDC LM9 castings due to gas porosity blistering risk. Full in-house T6 capability at Creative Alucast with batch hardness verification.
Applications
Typical Applications of LM9
| Industry | Typical Parts | Why LM6 |
|---|---|---|
| Automotive | Wheel hubs (LPDC), cylinder heads, structural brackets, safety-critical suspension parts | LPDC rating 4 + T6 strength — ideal for structural automotive |
| Power & Energy | High-pressure pump casings, hydraulic manifolds, compressor valve plates | Pressure tightness + T6 strength |
| Aerospace (commercial) | Structural housings, brackets, actuator bodies | Highest T6 tensile in standard LM series |
| Industrial | High-integrity castings requiring pressure testing and mechanical certification | T6 + low porosity from LPDC |
Wheel Hubs
Cylinder Heads
Structural Brackets
Hydraulic Manifolds
Compressor Parts
Safety-Critical Components
High-Pressure Pump Casings
Suspension Parts
LPDC Structural Parts
When NOT to Specify LM9
Do not specify LM9 when: (1) HPDC is required — rated ‘n’ (not recommended) for HPDC; use LM2 or LM24; (2) decorative anodising is required; (3) the application requires weldability — LM9 is not listed as easily weldable; (4) as-cast (M) condition strength is sufficient — use the simpler LM6 instead.
Frequently Asked Questions
Common Questions Abou LM9
What is the chemical composition of LM9 aluminium alloy?
LM9 per BS 1490:1988 has nominal composition Al-Si12Mg0.5Mn0.5. Silicon: 10.0–13.0%, Copper: —–0.20%, Magnesium: 0.2–0.6%. The remainder is aluminium with controlled impurity limits.
What is the EN 1706 / European equivalent of LM9?
The EN 1706 equivalent of BS 1490 LM9 is EN AC-43300, with chemical symbol designation EN AC-Al Si9Mg. This European standard supersedes the German DIN designation GD-AlSi10Mg.
What is the ASTM / AA equivalent of LM9?
The ASTM/Aluminium Association equivalent of LM9 is A360.0. Al-Si9Mg — primary US equivalent.
What is the JIS equivalent of LM9?
The JIS H 5302 equivalent of LM9 is ADC3. Al-Si-Mg die casting alloy.
What is the tensile strength of LM9?
The minimum tensile strength of LM9 is 295 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 LM9 be heat treated to T6?
Yes — LM9 is T6 heat-treatable (TF condition). Solution treat at 515–525°C, water quench, artificially age at 155–175°C. Full in-house T6 available at Creative Alucast with batch hardness verification.
What casting processes are suitable for LM9?
Per BS 1490:1988 Table 8: Sand casting (3), Gravity Die Casting (3), Low Pressure Die Casting (4), High Pressure Die Casting (n). Scale: 4=Excellent, 3=Good, 2=Fair, n=Not recommended.
What is the density of LM9 aluminium alloy?
The density of LM9 is 2.68 g/cm³ — approximately one-third the density of steel (7.85 g/cm³), making it ideal for lightweight structural applications.