A356 is one of the most important aluminium casting alloys. After heat treatment it offers an outstanding combination of strength, ductility and corrosion resistance, which is why it is the main alloy for aluminium car wheels and many safety-critical parts.
Chemical composition
A356 is an aluminium–silicon–magnesium alloy with about 6.5–7.5% silicon and 0.25–0.45% magnesium, and tight limits on iron and copper.
A356.0 versus A356.2
In the American standard, the number after the point shows the product form: A356.0 is the composition of the casting, and A356.2 is the composition of ingot for remelting, with much less iron (0.12% maximum). Less iron means fewer brittle phases and more ductility, so A356.2 is preferred for critical parts.
T6 heat treatment
The secret of A356's properties is the T6 heat treatment, which has three steps:
- Solution treatment: holding the part at a high temperature (about 540 °C) so that magnesium and silicon dissolve in the matrix.
- Quenching: rapid cooling to keep the solid solution supersaturated.
- Artificial ageing: heating at a lower temperature (about 150–170 °C) so that fine Mg2Si particles precipitate and strength rises.
Improving A356 quality
Adding strontium (Sr) changes the eutectic silicon from coarse needles to a fine fibrous form and increases ductility. Grain refinement with titanium–boron and careful degassing of the melt are also essential for the best properties.
Applications
Aluminium wheels, suspension and chassis parts, cylinder heads, aerospace components and marine equipment. Its close French equivalent, AS7G03, is widely used by Iranian parts makers.
Almas Aluminium produces A356.0, A356.2 and AS7G03 ingot. Try the alloy finder or contact the sales team.