Wall thickness
Keep walls uniform and as thin as the part allows. Eutectic grades (LM6, LM20) fill thin sections; thick, uneven sections invite shrinkage porosity in any alloy.
BS 1490 LM-Series
Aluminium Die Casting Alloy Guide
A practical reference for sourcing engineers: how to choose a BS 1490 LM-series aluminium casting alloy by your casting process and the property that matters most — castability, pressure-tightness, corrosion resistance, strength, wear or machinability — with a full comparison of all ten grades and their international equivalents.
Start Here
Choose by casting process first
The right alloy depends as much on how a part is made as on what it must do. Pressure die casting fills a steel die at high speed under pressure, so it favours fluid, eutectic alloys that resist hot-tearing in thin sections. Gravity die and sand casting fill more slowly, which suits heat-treatable grades that develop their strength after casting.
- Pressure die casting (PDC): LM2, LM6, LM20, LM24 and LM30 — fluid and tolerant of thin walls at volume.
- Gravity die & sand: LM4, LM9, LM13, LM25 and LM28 — heat-treatable grades for higher mechanical properties.
Most high-volume PDC work in India runs on LM24 (the international A380 / ADC10 family) because it casts cleanly, machines well and is forgiving of complex geometry. See how we apply it in aluminium pressure die casting.
Then choose by required property
- Castability / thin walls: the eutectic 12% silicon grades — LM6 and LM20 — fill intricate, thin sections best.
- Pressure-tightness & corrosion: LM6, LM20 and LM25 give leak-tight, corrosion-resistant castings for pumps, motors and marine or food contact.
- Strength: heat-treatable LM4, LM9 and LM25 reach higher mechanical properties after a T6-type cycle.
- Wear & low expansion: high-silicon LM13, LM28 and hypereutectic LM30 resist wear in pistons, bores and cylinder blocks.
- Machinability: copper-bearing LM4 and LM24 chip and finish predictably under CNC — see CNC machining.
Comparison Table
All ten LM-series alloys at a glance
Chemistry, international equivalents, heat-treatment, the casting process each suits and where it is typically used. International equivalents are approximate.
| Alloy | Int’l equivalent | Chemistry | Heat-treatable | Casting process | Typical applications |
|---|---|---|---|---|---|
| LM2 | ≈ A383 / ADC12 | Al-10Si-1.7Cu | No | Pressure die | Thin-section housings, covers, manifolds, automotive & electrical components. |
| LM4 | ≈ AA319 / EN AC-45000 | Al-5Si-3Cu | Yes | Gravity die, Sand | Gearbox & pump bodies, brackets, manifolds. |
| LM6 | ≈ A413 / ADC1 / EN AC-44100 | Al-12Si | No | Gravity/Sand/Pressure die | Thin, intricate, leak-tight, corrosion-resistant — marine, food, motor & pump housings. |
| LM9 | ≈ AlSi12Mg | Al-12Si-0.4Mg | Yes | Gravity die, Sand | Heat-treatable LM6 — higher strength & hardness. |
| LM13 | ≈ AlSi11CuMgNi (piston) | Al-11Si-Cu-Mg | Yes | Gravity die, Sand | Low expansion + wear resistance — pistons, engine parts. |
| LM20 | ≈ A413 / ADC1 / EN AC-44300 | Al-12Si | No | Pressure die | Pressure-die LM6 — thin, leak-tight, corrosion-resistant. |
| LM24 | ≈ A380 / ADC10 / EN AC-46000 | Al-8.5Si-3.5Cu | No | Pressure die | The PDC workhorse — gearbox cases, housings, brackets. |
| LM25 | ≈ A356 / EN AC-42100 | Al-7Si-0.3Mg | Yes | Gravity die, Sand | Premium, strength + corrosion — wheels, chassis, aerospace, food-grade. |
| LM28 | ≈ AlSi18CuNi (hypereutectic) | Al-18Si-Cu-Mg-Ni | Yes | Gravity die, Sand | Very low expansion + high wear — pistons. |
| LM30 | ≈ A390 / B390 / EN AC-48000 | Al-17Si-4.5Cu-Mg | Yes | Pressure die | Hypereutectic PDC — wear-resistant cylinder blocks/bores. |
BS 1490 LM-series · international equivalents are approximate · final selection also depends on wall thickness, post-treatment and supplier spec sheets.
Design for Manufacture
Get the geometry right, not just the grade
Alloy choice only pays off when the casting is designed to fill and solidify cleanly. A few DFM fundamentals to confirm on your drawing.
Draft & radii
Add draft to vertical faces for clean ejection and generous fillets at corners to ease metal flow and reduce stress concentration.
Gating & venting
Gates, runners and overflows are placed to fill progressively and push gas to vents — critical for pressure-tight, leak-free castings.
Post-treatment
Plan for heat treatment on LM4, LM9, LM25 and the piston grades, plus machining allowance and any coating, before the die is cut.
Final grade selection depends on your wall thickness, required mechanical properties and post-treatment, so treat the table as a starting point rather than a specification. Share your drawing for a confirmed grade and we will recommend the best alloy and route, whether the part suits high-pressure die casting or a heat-treatable gravity grade. For export buyers, see export aluminium castings, and explore heat-management parts in LED heat sink die casting.
Rank grades against your priorities in the interactive selector
Confirm Your Grade
Not sure which LM-series alloy fits your part?
Send your 2D drawing or 3D file with the finish and volume. We will confirm the alloy, casting process and a quote — usually within one business day.