Twin tip defects related to the nucleation and growth mechanisms of the twin (1012) in zinc characterized by high-resolution electron microscopy

Abstract

In order to determine the mechanisms of twin growth, a high-resolution electron microscopy study of the tip morphology in (1012) twin in zinc has been carried out. In a new model presented here, the twin tip is described as a series of (1012)//(1012) step faces, containing one or more interfacial dislocations. They are separated by incoherent (0001)//(1010) interfaces resulting from a pile-up of twinning dislocations. The stress around the twin tip is accommodated through the emission of (c + a)⅓ 〈1123〉 lattice dislocations and formation of residual dislocations b _D ≈ 0·47[1011] which are of the opposite sign to the twinning dislocation. This relaxation process can be associated with a blunting mechanism which finally stops the twin growth along the [1011] direction.