BS 1490 · Group A · General Purpose
LM16
Aluminium Alloy
Al-Si5Cu1Mg0.5 — High Strength and Pressure Tightness in Heat-Treated Condition
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-Si5Cu1Mg0.5
- 4.5–5.5 %
- 2.70 g/cm³
- 280 N/mm²
- 620–555 °C
- 138 W/m·K
- 80–100 HB
Overview
High Strength and Pressure Tightness in Heat-Treated Condition
LM16 is a medium-silicon alloy in the Al-Si-Cu-Mg system, combining the pressure-tightness benefits of moderate Si content with the heat-treatability provided by both copper (1.0–1.5%) and magnesium (0.4–0.6%). In the TF (T6) condition it delivers 280 N/mm² minimum tensile strength in chill casting — matching LM25 T6 performance while offering slightly better machinability from the Cu addition.
LM16 is rated for TB (solution treated + naturally aged) as well as TF (fully artificially aged) — making it the appropriate choice when strength is needed but full T6 artificial ageing is not available at the customer’s facility. The TB condition delivers 230 N/mm² minimum tensile in chill casting through natural ageing alone.
TB and TF Both Available
LM16 is one of the few LM alloys specified for both TB (naturally aged) and TF (artificially aged) conditions in BS 1490. This gives flexibility when the customer’s processing capability only allows natural ageing. Specify TB for 230 N/mm² minimum and TF for 280 N/mm² minimum in chill cast condition.
Chemical Composition
LM16 Chemical Composition — BS 1490:1988
| Element | Symbol | Min % | Max % | Role in alloy |
|---|---|---|---|---|
| Silicon | Si | 4.5 | 5.5 | 4.5–5.5% Si – lower Si range than LM9/LM6. Provides good castability without the machinability penalty of high-Si alloys. Alloy is not eutectic – wider freezing range requires careful feeding in heavy sections. |
| Copper | Cu | 1.0 | 1.5 | 1.0–1.5% Cu contributes to strength via CuAl2 precipitation during ageing. Also improves machinability. Cu content is lower than LM4, preserving better corrosion resistance. |
| Magnesium | Mg | 0.4 | 0.6 | 0.4–0.6% Mg is the primary T6 strengthening element via Mg2Si precipitation. Controlled to a tight range to ensure consistent T6 response. |
| Iron | Fe | — | 0.6 | Controlled to ≤0.6% – tighter than general-purpose alloys. LM16 is a structural alloy where ductility matters. |
| Manganese | Mn | — | 0.5 | Impurity limit. Controlled to maintain clean melt. |
| Nickel | Ni | — | 0.25 | 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
LM16 Equivalent Grades — International Standards
BS 1490
LM16
Group B · Special Purpose Al-Si5Cu1Mg0.5
EN 1706
EN AC-45300
EN AC-Al Si5Cu1Mg
ASTM / AA
355.0 / C355.0
355.0 is the primary US equivalent
JIS H 5302
—
No direct JIS equivalent
DIN 1725-2
G-AlSi5Cu1Mg
Superseded by EN 1706
ISO 3522
Al-Si5Cu1Mg
ISO casting alloy designation
Mechanical Properties
LM16 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 |
|---|---|---|---|---|---|
| TB | Sand / Investment | 170 | — | 2 | 80–90 |
| TB | Chill / GDC | 230 | — | 3 | 90–100 |
| TF | Sand / Investment | 230 | — | — | 90–105 |
| TF | Chill / GDC | 280 | — | — | 100–115 |
Physical Properties
LM16 Physical & Thermal Properties
Density
2.70 g/cm³
Approx. 1/3 the density of steel
Freezing Range
620–555 °C
Solidification temperature range
Thermal Conductivity
138 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
80–100 HB
As-cast or stated condition
| Property | Rating | Notes |
|---|---|---|
| Corrosion resistance | Good (B) | Better corrosion resistance than LM4/LM27 due to lower Cu content. Suitable for most engineering environments. |
| Decorative anodising | Poor (D) | Cu content limits anodising quality. Protective anodising is acceptable, but decorative anodising is not suitable. |
| Weldability | Fair | Weldable with care. Post-weld heat treatment is recommended to restore strength. |
| Machinability group | 3 — Good | Group 3 machinability. Cu addition improves chip formation compared with Cu-free alloys. |
Casting Suitability
LM16 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)
3
High Pressure (HPDC)
n
| Castability Property | Rating | Explanation |
|---|---|---|
| Fluidity | 3 — Good | Moderate Si gives good but not exceptional fluidity. Adequate for most geometries. |
| Resistance to hot tearing | 3 — Good | Good resistance to hot tearing. Wider freezing range than eutectic alloys requires correct feeding. |
| Pressure tightness | 3 — Good | Good pressure tightness when correctly cast. Used for pressure-tight hydraulic components. |
| Machinability (as-cast) | 3 — Good | Group 3 machinability. Cu addition improves chip formation compared with Cu-free alloys. |
Heat Treatment
LM16 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.
TB or TF — Both Specified in BS 1490
LM16 is specified for both TB (solution treat + natural age) and TF (solution treat + artificial age). TB gives 230 N/mm² chill cast minimum through room temperature ageing over several days — no ageing furnace required. TF gives 280 N/mm² and requires artificial ageing at 155–175°C. Full in-house TF capability at Creative Alucast.
Applications
Typical Applications of LM16
| Industry | Typical Parts | Why LM13 |
|---|---|---|
| Automotive | Pressure-tight hydraulic housings, engine brackets, structural castings | T6 strength + pressure tightness |
| Industrial | High-stress machine components, structural brackets, pressure vessels | Good combination of strength, machinability, and pressure tightness |
| Power & Energy | Pump bodies, compressor housings, valve bodies requiring mechanical certification | 280 N/mm² T6 + good pressure tightness |
Hydraulic Housings
Engine Brackets
Structural Castings
Pressure Vessels
Pump Bodies
Compressor Housings
Valve Bodies
Machine Components
When NOT to Specify LM16
Do not specify LM16 for HPDC — not recommended. For the most common T6 requirement, LM25 offers better corrosion resistance and broader foundry availability. Specify LM16 specifically when both TB (natural age) and TF options need to be available from the same alloy.
Frequently Asked Questions
Common Questions About LM16
What is the chemical composition of LM16 aluminium alloy?
LM16 per BS 1490:1988 has nominal composition Al-Si5Cu1Mg0.5. Silicon: 4.5–5.5%, Copper: 1.0–1.5%, Magnesium: 0.4–0.6%. The remainder is aluminium with controlled impurity limits.
What is the EN 1706 / European equivalent of LM16?
The EN 1706 equivalent of BS 1490 LM16 is EN AC-45300, with chemical symbol designation EN AC-Al Si5Cu1Mg. This European standard supersedes the German DIN designation G-AlSi5Cu1Mg.
What is the ASTM / AA equivalent of LM16?
The ASTM/Aluminium Association equivalent of LM16 is 355.0 / C355.0. 355.0 is the primary US equivalent.
What is the JIS equivalent of LM16?
There is no direct JIS H 5302 equivalent for LM16. No direct JIS equivalent.
What is the tensile strength of LM16?
The minimum tensile strength of LM16 is 280 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 LM16 be heat treated to T6?
Yes — LM16 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 LM16?
Per BS 1490:1988 Table 8: Sand casting (3), Gravity Die Casting (3), Low Pressure Die Casting (3), High Pressure Die Casting (n). Scale: 4=Excellent, 3=Good, 2=Fair, n=Not recommended.
What is the density of LM16 aluminium alloy?
The density of LM16 is 2.70 g/cm³ — approximately one-third the density of steel (7.85 g/cm³), making it ideal for lightweight structural applications.