AlSi5Mg0.3 ALLOY FOR THE MANUFACTURE OF AUTOMOTIVE WHEELS

The heat-treated AlSi7Mg0.3 alloy is the standard wheel alloy as it offers the best compromise between fatigue strength and elongation. Alloys with less than 7 wt% Si may also be of interest for the manufacture of aluminium wheels to limit Si poisoning that impairs grain refinement. Hence, the potential of AlSi5Mg0.3 alloy was investigated as it could offer superior mechanical properties owing to a smaller grain structure. AlSi5Mg0.3 alloy does indeed exhibit smaller grains but fails to offer higher mechanical properties. AlSi7Mg0.3 alloy with a smaller dendritic structure but coarser grains is superior. The higher fluidity of the latter is believed to offer better feeding characteristics, which in turn improves the soundness of the casting and thus leads to superior structural quality and mechanical properties. An overall industrial assessment favours the standard Al7Si0.3 Mg alloy in the manufacture of light alloy wheels.