Diffusion induced grain boundary migration in Ni-Cu Diffusion couples

Abstract

Diffusion induced grain boundary migration (DIGM) was investigated in the Ni substrate of Ni-Cu diffusion couples. After annealing at 615°C for 26 h, TEM/STEM revealed: 1. (1) dislocation walls at the initial grain boundary positions, 2. (2) a small misorientation (0.1–0.5°) between the DIGM zone and the Ni matrix, 3. (3) highest Cu concentrations in the DIGM zones adjacent to the original grain boundary positions, 4. (4) steps and line defects at the DIGM boundaries and 5. (5) grain boundary faceting caused by DIGM. After 92 h of annealing at 615°C, two major changes were observed as compared with the shorter 26 h anneal at the same temperature: 1. (1) a decrease in the dislocation densities in the DIGM zones, in the matrix and at the original grain boundary positions 2. (2) a change in Cu concentration profiles across the DIGM zones. The experimental results are interpreted in terms of current DIGM theories.