L M 25 is an aluminium alloy that conforms to BS 1490 and is particularly suitable for use in high quality castings where strength, definition and good corrosion resistance is important. Alloys with similar chemical composition are used throughout the world, see below for details.
LM 25 is a high purity aluminium alloy, which can be gravity diecast in permanent moulds or sand. It has excellent castability and good mechanical properties that can be varied by heat treatment. The alloy is mostly used for high specification castings in industries where shape and complex form is required and casting soundness is important. Its use is widespread in the automotive industries for alloy wheels, cylinder heads and blocks and in many other industries such as chemical, marine and electrical.
Castings made from this alloy can be supplied in the as cast form or in one of three other heat treated conditions.
It should be noted that there is no significant advantage to be gained from heat treatment if the service conditions envisaged are likely to include extended periods at temperatures above 130°C. However, hardness, tensile strength and elongation can be significantly improved by heat treatment. Castings in this can be supplied in the M, TE, TB 7 and TF conditions.
This alloy has excellent resistance to seawater attack and can be anodised to improve its corrosion resistance. Anodising will give a grey / opaque finish suitable for dark decorative finishes only. LM 25 also has good machining characteristics and can be welded if required.
This alloy is similar to the following international specifications:
| France | Germany | Italy | USA | Japan | Australia |
|---|---|---|---|---|---|
| A-S7G | G-AlSi7Mg | UNI 3599 | A356 | AC 4CAC | AA601/AC601 CC601/DA601 |
| Alloy Destination | Al SiMg0.5 | Colour Code | Yellow + Blue |
| Short Destination | LM 25 | Alloy Number | N/A |
| Chemical composition of ingots. BS 1490 1988 | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cu | Si | Mg | Fe | Mn | Ni | Zn | Pb | Sn | Ti | Others | Total | |
| Minimum | - | 6.5 | 0.20 | - | - | - | - | - | - | - | Each | - |
| Maximum | 0.20 | 7.5 | 0.6 | 0.5 | 0.3 | 0.1 | 0.1 | 0.1 | 0.05 | 0.2 | 0.05 | 0.15 |
| Mechanical Properties (Supplied in diecast form) |
Minimum | Maximum |
|---|---|---|
| Tensile strength | 160 MPa | 200 MPa |
| 0.2% Proof stress | 80 MPa | 100 MPa |
| Impact Strength Charp | - | - |
| Elongation | - | 2-3% |
| Shear Strength | - | - |
| Modulus of Elasticity x 103 | - | 71 MPa |
| Fatigue Strength 5 x 108 cycles | 80 MPa | 110 MPa |
| Hardness BHN | 55 max | 65 max |
| Physical Properties | |
|---|---|
| Melting Range | 615 - 550°C |
| Density | 2.68g/cm3 |
| Coefficient of Thermal expansion per °C at 20-100°C | 0.000022 |
| Thermal Conductivity cal/cm2/°C at 25°C | 0.36 |
| Electrical Conductivity | 39% IACS |
| Electrical Resistivity | -- |
Content supplied by Brock Metal