Aluminium Casting Alloy LM6

Aluminium Alloys

LM6 ALUMINIUM CASTING ALLOY SUMMARY

This alloy complies with the BS 1490:1988 LM6 specification.

CHEMICAL MAKEUP

	%		%		%
Copper	0.1 max	Magnesium	0.10 max	Silicon	10.0-13.0
Iron	0.6 max	Manganese	0.5 max	Nickel	0.1 max
Zinc	0.1 max	Lead	0.1 max	Tin	0.05 max
Titanium	0.2 max	Aluminium	Remainder	Others each	0.5 max
Others total	0.15 max

MECHANICAL PERFORMANCE OF LM6 (SAND & DIECASTING)

	SAND CASTING	PRESSURE DIE CASTING	GRAVITY DIE CASTING
0.2% Proof Stress (N/mm²)	60–70	120	70–80
Tensile Strength (N/mm²)	160–190	280	190–230
Elongation (%)	5	2–5	7
Impact resistance Izod (Nm)	6.0	-	9.0
Brinell Hardness	50–55	55–60	55–60
Modulus of Elasticity (×10³ N/mm²)	71	71	71
Shear Strength (N/mm²)	120	-	-

HIGH-TEMPERATURE BEHAVIOUR

The tensile strength and hardness of this aluminium casting alloy decline steadily as temperature increases, becoming notably poor by around 250°C.

PHYSICAL CHARACTERISTICS OF LM6 (SAND & DIECASTING)


Coefficient of Thermal Expansion (per °C @ 20–100°C)	0.000020
Thermal Conductivity (cal/cm²/cm/°C @ 25°C)	0.34
Electrical Conductivity (% copper standard @ 20°C)	37
Density (g/cm³)	2.65
Freezing Range (°C) approx.	575–565

MACHINING QUALITIES

Alloys in this family, including LM6, tend to be harder to machine because they drag during cutting and cause rapid tool wear due to their high silicon content. Using carbide tools with generous rake angles and slower cutting speeds produces better outcomes when combined with adequate coolant and lubricant.

RESISTANCE TO CORROSION

LM6 demonstrates strong corrosion resistance under typical atmospheric and marine conditions. For more extreme environments, this resistance can be further improved through anodic treatment.

ANODISING SUITABILITY

LM6 accepts standard anodising processes well, producing surface films that range from light grey to deep brown depending on the treatment.

USES AND PRACTICAL NOTES

With excellent corrosion resistance and very good casting behaviour, LM6 is widely used for marine ‘on-deck’ components, water-cooled manifolds, jackets, motor-car and road-transport fittings, and intricate shapes such as motor housings, meter cases, or switch boxes. It is also preferred for large aluminium castings such as door panels and pumps where easy flow and castability are essential. Beyond marine and automotive, LM6 is valued in chemical and dye-industry applications, agricultural machinery, and food-processing equipment.

Its ductility allows LM6 castings to be straightened or altered in form if needed, making it suitable for parts requiring post-casting adjustment. The alloy is versatile for sand casting and aluminium die-casting processes, including gravity and pressure die casting.

Although LM6 performs very well in marine environments and offers excellent ductility, its strength is moderate, and it is not heat-treated. Its high-temperature performance drops off quickly, the alloy has a low elastic limit, and machining remains challenging.