Fatigue properties of a cast aluminium alloy for rims of car wheels

Abstract

Thanks to the potential weight saving, aluminium castings are good candidates for automotive, electronic, aeronautic, sport equipments and other high performance products. At present, one of the main limits to a wide use of aluminium alloys for these applications is a lack of complete understanding of their fatigue behaviour and of the relationships to microstructural features, particularly as far as casting alloys are concerned.

In this paper, the rotating bending fatigue behaviour of a cast Al-10Si-0.6Cu alloy has been investigated. The specimens for both the fatigue tests and the microstructural analyses have been drawn directly from the rims of car wheels. The wheel design influences the microstructure of the alloy, conditioning the cooling rate during solidification and, of consequence, may have important effects on the wheel fatigue performances.
Measurements of the sizes of the microstructural constituents, such as secondary dendrite arm spacing and of porosity, have been also carried out by means of optical microscopy, supported by an image analysis software.
Rotating bending fatigue tests have been performed on specimens with different types of notches. In this way, after the fatigue tests, it was possible to study the effect of the wheel design and so, of stress concentrations, on the fatigue life.