Twin tip defects related to the nucleation and growth mechanisms of the twin (10(1)over-bar-2) in zinc characterized by high-resolution electron microscopy

摘要

In order to determine the mechanisms of twin growth, a high-resolution electron microscopy study of the tip morphology in (10 (1) over bar 2) twin in zinc has been carried out. In a new model presented here, the twin tip is described as a series of ((1) over bar 012)//((1) over bar 01 (2) over bar) step faces, containing one or more interfacial dislocations. They are separated by incoherent (0001)//(10 (1) over bar 0) interfaces resulting from a pile-up of twinning dislocations. The stress around the twin tip 1 is accommodated through the emission of (c + a)1/3(11 (2) over bar 3) lattice dislocations and formation of residual dislocations b(D) approximate to 0.47[(1) over bar 011] 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 [10<(11)over bar>] direction.