Mechanical and Casting Properties of Alloys Used for Automobile Wheels.

The demand for cast automobile wheels has grown steadily in recent years, being estimated in 1980 at more than 7 million units in Western Europe, with a growth rate averaging 6 to 7% per annum. This article discusses the mechanical properties (static and dynamic) and the casting properties of the alloys employed in the manufacture of automobile wheels. Mechanical properties are considered in turn for: (1) Those alloys which are not heat-treatable. The two families, Al-Si7 MgSb and Al-Si11 MgSr, are compared at various levels of magnesium content. (2) Those alloys which are heat-treatable. The Al-Si7 Mg0. 3 grades are compared with other potentially usable alloys. The question of the partial heat treatment associated with paint stoving (artificial aging effect) and how this interacts with the effects of cooling of the casting on release from the mold is also discussed. The casting properties of Al-Si7 Mg and Al-Si11 Mg alloys are compared using conventional testpieces and also samples taken from wheels cast by the low-pressure process.