Papers by Author: Andrew J. Moffat

Abstract: Fatigue initiation behaviour in three multi-component Al-Si casting alloys with varying Si content is compared using a range of microscopy and analytical techniques. A higher proportion of stiffer secondary phases leads to load transfer effects reducing particle cracking and particle/matrix debonding. Si appears stronger than the Al9FeNi phase, which cracks and debonds to form initiation sites preferentially over Si. Reducing Si content results in clusters of intermetallics forming, and increased porosity. The effect of porosity, combined with mesoscopic load transfer effects to the high volume fraction intermetallic regions make these potent crack initiation sites in low silicon alloys.

Abstract: Microscale fatigue damage mechanisms in various Al-Sn-Si based bearing alloys used as linings of plain automotive bearings are reported. Extensive work on previously developed alloys has concluded that secondary phase particles such as Sn and Si are potential fatigue initiation sites with a complex combination of various particle geometry parameters. A newly developed alloy contains a number of complex widely scattered intermetallics with much finer and fewer Sn and Si particles. This alloy system appears to be more resistant to initiate microscale fatigue damage compared to the previous systems.