Multiscale analyses of the interaction between dislocation and sigma 9 symmetric tilt grain boundaries in Fe-Si bicrystals by nanoindentation technique

Dislocation-grain boundary (GB) interaction plays a crucial role in the strengthening mechanism of polycrystalline metals. In this study, we evaluated the interaction between dislocation and two types of Sigma 9 symmetric tilt GBs using combined experimental and computational nanoindentation analyses. The experimental and simulation results are obtained at different spatial scales and are complementary. Experimental nanoindentation, in which the indent position was 1.0 mu m offset from the GBs, showed that a considerable plastic zone was formed in the adjacent grain in the case of Sigma 9{114}, whereas this zone was absent in the case of Sigma 9{221}. Atomistic analysis provided information on the activated Burgers vector caused by a large resolved shear stress and the change in the GB structure due to dislocation absorption. Moreover, from experimental and computational nanoindentation analyses of the case in which the indent position was exactly on the GB, it was found that the load required for dislocation nucleation from the GB in Sigma 9{221} was slightly higher than that in the case of Sigma 9{114}. Dislocation trajectories observed in the on-GB experiments were similar to those in the on-GB simulations, where an activated Burgers vector was detected. The origin of the effects of GBs on dislocation transmission and nucleation was discussed based on the mechanical responses and dislocation behaviors obtained in experiments, activated slip directions in atomistic simulations, and theoretical models for dislocation-GB interaction.