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Aluminium Gravity Die 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.
Mechanical Properties
| M Gravity Die Cast | TF Sand Cast | TF Gravity Die Cast | TE Sand Cast | TE Gravity 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 |
Physical Properties
| Value | |
|---|---|
| Coefficient of Thermal Expansion (per C @ 20-100 C) | 0.000022 |
| Thermal conductivity (cal/cm2/cm/ C @ 25 C) | 0.36 |
| Electrical conductivity (% copper standard @ 20 C) | 39 |
| Density (g/cm3) | 2.68 |
| Freezing range (C) approx. | 615-550 |
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.
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.
Application and General notes
Having high resistance to corrosion and excellent castability, aluminium LM6 is suitable for most marine 'on deck' castings, water-cooled manifolds and jackets, motor car and road transport fittings, thin section and intricate castings such as motor housings, meter cases and switch boxes, for a very large aluminium casting, e.g. cast doors and panels where ease of casting is essential, for chemical and dye industry castings, e.g. pump parts, and for paint industry and food and domestic castings. It is especially suitable for castings thatare to be welded. The ductility of LM6 enables castings to be rectified easily or even modified in shape, e.g. simple components may be cast straight and later bent to the required contour.
LM6 is equally adaptable for sand casting and aluminium die casting(gravity die casting and pressure die casting). It has excellent resistance to corrosion in marine environments, possesses excellent ductility, but is of medium strength and is not heat treated. Its strength falls off rapidly at high temperatures. Its elastic limit is low and there is difficulty with machining.