Zonal dislocations mediating image twinning in magnesium Original Research Article

The twin boundary (TB) interfacial structure and the configuration of zonal twinning dislocations for image twin growth in magnesium have been investigated by using molecular dynamics simulations and transmission electron microscopy (TEM). The simulation results show that twin growth is initially dominated by the motion of existing TB steps. After these steps, the twin growth is mediated by the nucleation and glide of new zonal dislocations at the TBs. The steps and the twinning dislocations have Burgers vectors of 1bT, 2bT and 4bT, where image is the Burgers vector of the elementary twinning dislocation. The favorable zonal dislocation is 2bT, which can be viewed as the image matrix dislocation spreading over two image layers to accomplish the twinning relationship across the TB. The connection established between the twinning and the dislocation slip in the matrix is supported by TEM observations.