HIGH-TEMPERATURE DEFORMATION AND FRACTURE-BEHAVIOR OF CU-SIO2 BICRYSTALS

Bicrystals of Cu-SiO//2 dispersion hardened alloys and pure copper were tensile tested between 450 and 1050 K at a strain rate of 1. 5 multiplied by 10** minus **4 sec** minus **1. In the case of pure copper bicrystals, elongation to fracture did not depend significantly on temperature and the fracture mode was transgranular up to 850 K. On the other hand, ductility decreased with increase in temperature and the transition in the fracture mode from transgranular to intergranular occurred at around 450 K. SiO//2 particles on grain boundaries play an important role in intergranular fracture by suppressing grain boundary sliding and retardation of recrystallization during deformation. Two types of Cu-SiO//2 bicrystals having different crystal orientation relationships show different deformation and fracture behaviour. This can be explained in terms of the contribution of lattice dislocations to the grain boundary sliding.