Ageing effect on serrated flow in Al-Mg alloys

Serrated flow was investigated in Al-1Mg and Al-5Mg alloys that were quenched and aged at 453 K for different durations. Tensile tests were performed at temperatures ranging from 243 to 353 K. Changes in critical strain and types of serrations with the testing temperature are similar for the as-quenched and 24 h aged alloys. Distributions of the stress drops of serrations were evaluated. The peak position of the distribution moves to a small value after 24 h of ageing in Al-1Mg. In contrast, the peak positions shift first to large and then to small values with increasing ageing times in Al-5Mg. The distributions of the stress drops change from asymmetric --> symmetric --> asymmetric with increasing testing temperature. However, no corresponding change in types of serrations and characteristics of stress drop distributions with flow stress was found. (C) 2002 Elsevier Science B.V. All rights reserved.