Nucleation of dynamic recrystallization at grain boundaries in copper bicrystals

The nucleation mechanisms of dynamic recrystallization (DRX) were investigated in copper bicrystals deformed in tension at 923 K at a strain rate of 4.2 x 10(-4) s(-1). The boundary plane was either parallel or inclined to the tensile axis. The grain boundaries were observed to migrate locally and to form bulges. Nuclei appeared preferentially at the migrating grain boundaries at a strain as low as epsilon = 0.15 i.e. only about half of the peak strain. All nucleated grains were identified as twins (Sigma3) to one of the two adjacent crystals. The twinning planes coincided preferentially with a secondary slip plane of the adjoining crystals. The DRX nucleation mechanisms at grain boundaries are discussed with respect to grain boundary migration and recrystallization twinning. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.