Clustering in Al–3Cu–0·1 Be

Abstract

The aging behaviour of Al–3Cu and Al–3Cu–0·1Be alloys has been investigated using microhardness and transmission electron microscopy techniques. The Al–3Cu–0·1 Be alloy was found to have a significantly higher hardening rate than the Al–3Cu alloy at room temperature and 110°C. An Al–0·2Be alloy showed no age hardening tendency at room temperature. The hardening in Al–3Cu alloy is the result of Guinier–Preston (GP) zone formation; no GP zones were observed in Al–3Cu–0·1Be alloy aged at room temperature and 110°C, and an additional aging at 150°C was required to initiate GP zone formation. The higher hardening rate for the Al–3Cu–0·1 Be alloy is attributed to the early and extensive formation of vacancy loops adjacent to network dislocations, the loops acting as barriers to the glide of network dislocations. The formation of Cu–Be–vacancy clusters may be the cause of the accelerated hardening rate, and this is discussed.

MST/309