Unstable Dislocations in Anisotropic Crystals

Abstract

Abstract In an elastically anisotropic crystal, the energy of a dislocation depends on the crystallographic direction of the dislocation line. A straight dislocation which is in a high energy direction may be unstable with its energy decreasing if it changes to a zig‐zag shape. The relation between two different criteria of instability is clarified. The theory is used to examine seven possible slip systems in three metals. Instabilities are predicted for six systems in β‐brass, two in iron, and none in niobium. Tables are given of the predicted instabilities for the 〈110〉 {111} f.c.c. system and the 〈111〉 {110} b.c.c. system for a range of elastic constants. A preliminary report is given of the observation of this phenomenon in β‐brass.