LM9

Aluminium Casting Alloy LM9

This alloy conforms to BS:1490 1988 LM9. Castings are standardised in the as cast (M) condition, in the precipitation treated (TE) condition or in the fully heat treated (TF) condition.

Chemical Composition

	%		%		%
Copper	0.2	Magnesium	0.2-0.6	Silicon	10.0-13.0
Iron	0.6	Manganese	0.3-0.7	Nickel	0.1 max
Zinc	0.1	Lead	0.1 max	Tin	0.05 max
Titanium	0.2	Aluminium	Remainder	Others each	0.05 max
Others total	0.15 max

Mechanical Properties of Aluminium (Sand & Die Casting) Alloy LM9

	M Gravity Die Cast	TF Sand Cast	TF Gravity Die Cast	TE Sand Cast	TEGravity Die Cast
0.2% Proof Stress (N/mm²)	95-120	220-250	270-280	110-130	150-170
Tensile Strength (N/mm²)	190	240	295	170	230
Elongation (%)	3-5	0-1	0-1	1.5	2
Impact Resistance Izod (Nm)	-	0.7	1.4	1.4	2
Brinell Hardness	75-85	95	110	70	85
Modulus of Elasticity (10³ N/mm²)	-	71	71	71	71
Shear Strength (N/mm²)	-	200	230	120	160

Strength at Elevated Temperatures

Tensile properties are unaffected by temperatures up to 150°C but prolonged heating at temperatures significantly higher reduces the strength. For example, the tensile strength of chill cast LM9-TF at 200°C (after heating for 500h) is approximately half that at room temperature, and only 25% of the original value at 250°C.

Physical Properties of Aluminium (Sand & Die Casting) Alloy LM9


Coefficient of Thermal Expansion (per °C @ 20-100°C)	0.000022
Thermal conductivity (cal/cm²/cm/°C @ 25°C)	0.35
Electrical conductivity (% copper standard @ 20°C)	38.0
Density (g/cm³)	2.68
Freezing range (°C) approx.	575-550

Machinability

Very considerable tool wear occurs in machining this aluminium alloy, but there is not the same tendency to drag that occurs with high Silicon alloys containing no other alloying elements, e.g. LM6. Carbide-tipped tools with large rake angles and relatively low cutting speeds give good results. A cutting lubricant and coolant should be employed.

Corrosion Resistance

LM9 exhibits excellent resistance to corrosion under both ordinary atmospheric and marine conditions.

Anodising

LM9 Can be anodised by any of the common processes, the resulting protective film ranging in colour from grey to dark brown, depending on the method employed.

Heat Treatment

Heat Treatment produces high strength and hardness

Applications and General Notes

LM9 alloy is used where the fluidity and corrosion resistance of LM6 are required with high strength and hardness. It is equally suitable for sand casting and gravity die casting and is extensively used for low pressure castings, for cover plates and instrument cases. It is useful for electroplated components. LM9 has poor weldability and brazeability.

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