Hot isostatic pressing of Cu–Bi polycrystals with liquid-like grain boundary layers

The grain boundary segregation in an Cu–50 at.ppm Bi alloy annealed at two temperatures and under various hydrostatic pressures in a hot isostatic pressing apparatus was investigated by means of Auger electron spectroscopy. It was found that high pressures have only little effect on grain boundary segregation. At a temperature of 973 K the segregation level remained approximately constant at 2 monolayers of Bi for all pressures studied. Some decrease of the grain boundary segregation with increasing pressure was observed at 1173 K. It was also demonstrated that the segregation level in the alloy treated at 0.01 GPa depended on the sample cooling rate after annealing. The observed pressure dependence of Bi segregation to the grain boundaries was interpreted in terms of non-equilibrium segregation during specimen cooling.