Dislocation Motion in an Impure Crystal I. Steady Motion

Abstract

A stochastic theory of dislocation motion in an impurity field is developed. Unpinning process of a dislocation segment is treated as motion of one particle, where the flexible nature of the dislocation is taken into account by introducing an effective external stress. For large viscosity case, the problem reduces to that of diffusion. The steady motion of the dislocation is obtained as a function of external stress, impurity potential, and temperature. It is found that in medium stress range the velocity is proportional to high power of external stress as obtained experimentally. The impurity concentration dependence is also discussed. The results are compared with experiments to give a sufficient agreement.