Fatigue crack propagation in Al–Sn bearing alloys

Abstract

Fatigue crack propagation has been studied in a series of Al–Sn bearing alloys as a function of microstructure and environment at stress intensity ratios R of 0·7 and 0·1. Fatigue thresholds of tin containing alloys increased with a reduction in content and in continuity of the tin phase in laboratory air. This is interpreted in terms of crack closure, crack growth along the Al/Sn interface, and crack tip blunting mechanisms. Mechanisms that retard fatigue crack growth through the aluminium phase (e.g. by an increase in the reversibility of slip or by an increase in the size of the reverse plastic zone) were found to increase fatigue thresholds. When tested in dry air, the Al/Sn interface shows reduced embrittlement. The consequence of this for fatigue thresholds is complex: at R=0·7, fatigue thresholds increase with a decrease in tin content, while the thresholds are constant at R=0·1.

MST/927