The effect of particle size and spacing on the retardation of recrystallization in two-phase copper crystals

Abstract

The effect of stable dispersion of Al₂O₃ in copper crystals upon recrystallization kinetics has been studied in three alloys, termed L1, L2 and H2, and in pure copper. L1 and L2 contained particles of similar size (0.028μm), but of differing interparticle spacing, and L1 and H2 contained particles of similar spacing (0.05μm) but of differing size. After a cold-rolling reduction of 50%, alloys L1 and L2 showed retarded recrystallization at 700° C compared with pure copper, there being greater retardation in L2, which had the smaller inter-particle spacing. Extensive recovery prior to recrystallization was observed and this led to deviations from the Avrami equation in describing the recrystallization kinetics. Calculations show that the retardation cannot be due to grain-boundary or sub-boundary pinning by the dispersed phase, and it is concluded that the effect is due to the homogenization of dislocation distribution by the particles suppressing nucleation. Alloy H2 contained larger particles (0.041μm), and exhibited accelerated recrystallization compared with pure copper. This indicates that a very delicate balance must exist between the factors tending to retard and those tending to accelerate recrystallization in these materials. It is suggested that the acceleration arises from an increased misorientation developing within the transition bands.