The influence of elastic anisotropy on dislocation stability in /gb-tin and lead

The effects of elastic anisotropy on the energy and thermodynamic stability of dislocations in β-tin and lead were assessed through computation of the dislocation energy factorK. The energy factors were utilized to construct an inverse Wulff plot, from which unstable dislocation orientations are defined by concave regions of the construction. Dislocation instabilities are predicted for β-tin near the melting point for four of six slip systems considered, the slip systems displaying the instabilities being (110) [001], (100) [001], (010) [101], and (101)[101]. An instability is predicted also for the slip system {111} <111> in lead, which is the first fcc metal found to display sufficient elastic anisotropy for instability. For the metals examined in this paper, the angular range over which instabilities occur narrows with decreasing temperature, and usually, below some critical temperature, the dislocation line becomes stable over all orientations. The occurrence of dislocation instabilities is a direct result of elastic anisotropy, and their possible influence on physical properties is discussed.