Migration of 〈100〉 tilt grain boundaries in high purity lead

Abstract

Measurements are obtained of the activation energies for grain boundary migration in bicrystals of zone-refined lead as a function of misorientation about a common 〈100〉 tilt axis. The plot of activation energy versus misorientation shows the presence of minima at orientation differences near 23°, 28° and 37°. These grain boundary angles, which gave the lowest activation energies, namely 5–6 kcal/g. atom, correspond to predicted coincidence site orientation relationships about 〈100〉. The dependence of boundary velocity on misorientation is found to be greater than that predicted by the dislocation core model. Some evidence is presented, based on twinning observations, which indicates that certain boundaries of the 〈113〉, 〈120〉, 〈123〉 and 〈320〉 type are relatively low density coincidence site boundaries.