Quasi-four-dimensional analysis of dislocation interactions with grain boundaries in 304 stainless steel

The application of diffraction contrast electron tomography to dynamic experiments involving dislocation interactions with grain boundaries is demonstrated for the first time. Two applications are shown: the first is concerned with post-mortem analysis of dislocation interactions with grain boundaries and illustrates the usefulness of the tomography technique for defect analysis; the second is in conjunction with in situ straining experiments in which the dynamics of dislocation interactions with grain boundaries are observed directly and the resulting structure visualized three-dimensionally. The in situ straining experiments were conducted at room and elevated temperatures to determine the influence, if any, of thermal processes on the slip transfer mechanism. It was found that increasing the temperature lowers the barrier for dislocation absorption and emission from the boundary and increases the complexity of the interactions, but does not change the fundamental mechanisms governing slip transmission. Previous experimentally determined criteria for slip transmission across boundaries were extended to interactions involving partial dislocations, where it was found that the reaction continues to be governed predominately by reduction of the Burgers vector of the residual grain boundary dislocation left after slip transfer.