Deposition of material at grain boundaries in tension interpreted in terms of diffusional creep

We propose that the deposition of material at grain boundaries in tension may be used as a critical test for diffusional creep. According to the contemporary understanding of grain boundary structures, material is deposited at grain boundaries by the climb of grain boundary dislocations (GBDs). In the general case, climb and glide are coupled processes and since GBDs are associated with a step in the boundary, the movement of a grain boundary dislocation by climb and glide will result in concurrent grain boundary migration. We describe an experiment that unambiguously separates the components of deposition, grain boundary sliding and migration. The experiment has been applied to a sample of Cu–2wt.%Ni which was crept to an elongation of 2.4% under a stress of 1.14 MPa at 1073 and 1103 K. It was demonstrated that material had been deposited at some of the grain boundaries in tension during the creep deformation.