ADC12, LM6 and LM24 are three of the most commonly traded aluminium casting alloys in India. All three are aluminium-silicon alloys sold as secondary ingots, but they behave differently in the die and in service. Picking the wrong one can mean porosity, cracking, poor machining or a part that corrodes early. This guide explains the differences in plain terms and what to agree with a supplier before you place an order for alloy ingots.
The three alloys in brief
ADC12 is a Japanese (JIS) die-casting alloy, roughly AlSi11Cu3. It has high silicon for fluidity and some copper for strength and machinability. It is the workhorse alloy for pressure die-cast parts such as gearbox housings, motor covers, brackets and two-wheeler components. Read more on ADC12.
LM6 is a British standard alloy, roughly AlSi12, close to the aluminium-silicon eutectic. It has very low copper, which gives it excellent fluidity, good corrosion resistance and good ductility for a casting alloy. It is often used for thin-walled or intricate gravity and sand castings, marine fittings and parts exposed to weather. See LM6.
LM24 is also a British standard die-casting alloy, roughly AlSi8Cu3Fe, broadly similar to the American A380 type. It has less silicon than ADC12 or LM6 and more copper, giving good strength and machinability in pressure die-casting.
Approximate chemistry
The figures below are rounded, indicative ranges for comparison only. Always buy against the latest edition of the relevant standard or your own drawing specification.
| Element | ADC12 | LM6 | LM24 |
|---|---|---|---|
| Silicon (Si) | about 9.6 to 12 | about 10 to 13 | about 7.5 to 9.5 |
| Copper (Cu) | about 1.5 to 3.5 | very low (around 0.1 max) | about 3 to 4 |
| Iron (Fe) | up to about 1.3 | low (around 0.6 max) | up to about 1.3 |
| Zinc (Zn) | up to about 1 | very low | allowed at higher levels |
| Typical process | pressure die-casting | gravity, sand, some die-casting | pressure die-casting |
How they compare in practice
- Fluidity: LM6 flows best because it is near-eutectic, so it fills thin sections and fine detail. ADC12 is also very fluid. LM24 is slightly less fluid but still well suited to die-casting.
- Strength and hardness: the copper in ADC12 and LM24 raises strength and hardness. LM6 is softer but more ductile.
- Corrosion resistance: low-copper LM6 is clearly better. Copper-bearing alloys are fine for most enclosed or painted parts but less suited to marine or outdoor exposure without protection.
- Machinability: ADC12 and LM24 machine well. LM6 can be gummy and is harder on tools because of the high silicon.
- Iron tolerance: die-casting alloys allow more iron because iron reduces die soldering. In gravity casting, high iron forms needle-like intermetallics that make parts brittle, which is why LM6 keeps iron low.
Which one should you choose?
Start with the process and the part. For high-volume pressure die-cast housings and covers, ADC12 or LM24 is usually the choice; many customers specify one of these by name, so check the drawing first. For gravity or sand castings with thin walls, or parts that will face moisture, salt or chemicals, LM6 is the safer option. If a part needs heat treatment for higher strength, neither ADC12 nor LM24 is ideal; buyers often look at an Al-Si-Mg alloy such as LM25 / A356 instead. Our blog on choosing an alloy for die-casting covers more options.
What to check when buying alloy ingots
- Composition report per lot: ask for a spectro analysis report from each heat, not a generic sheet. Check Si, Cu, Fe, Zn, Mg and Mn against your limits.
- Iron and zinc: secondary ingots made from mixed scrap can drift high in iron and zinc. Agree firm maximums.
- Sampling and disputes: agree who takes the sample, from how many ingots, and which lab result settles a disagreement.
- Ingot condition: ingots should be clean, dry and free of dross inclusions. Moisture in ingots is dangerous when charged into molten metal.
- Weight per piece and packing: confirm bundle weight and strapping so it suits your furnace and handling.
- Consistency: for regular supply, ask how the supplier controls scrap input and melt chemistry from lot to lot.
Equivalents and naming
Buyers often use names loosely. ADC12 is frequently compared with A383 or LM24, and LM6 with A413-type alloys, but these are not exact equivalents; limits differ, especially for copper, iron and zinc. When you post a requirement, quote the exact standard and grade from your drawing. If your customer allows alternates, state which ones are acceptable so suppliers can quote more options.
Sourcing through AluminumBazaar
Post your requirement with alloy, quantity, delivery location and any chemistry limits. The sourcing desk collects quotations from verified ingot makers with rate, GST, freight and payment terms, and can arrange a sample and spectro check before you commit to a full truckload.