Effect of high pressure on grain boundary migration in aluminium bicrystals

Abstract

The effect of high pressures on the migration rate of grain boundaries (GBs) in aluminium bicrystals was studied. The boundaries were of tilt type, with 〈111〉, 〈100〉 and 〈110〉 tilt axis. For each tilt axis at least two boundaries were studied, one with periodic and another with non‐periodic structure. It was found that for the 〈111〉 and 〈100〉 boundaries the activation volumes (V*) for migration were independent both on the activation energy and on misorientation. The obtained values were close to 1.2 atomic volume (Ω), which corresponds to V* for self‐diffusion. For the four 〈110〉 boundaries investigated V* was proportional to the activation energy and was in the range 1.1–3.6 Ω. These results indicate that in 〈111〉 and 〈100〉 boundaries GB migration takes place by single atom transfer, with cooperation of one vacancy. In the case of 〈110〉 boundaries it takes place by transfer of groups of atoms by a multi‐vacancy‐mechanism.