Influence of loading directions on dislocation slip mechanism of nanotwinned Ni with void defect at the twin boundary

In this study, a molecular dynamics model is used to simulate the compressive loading process along different crystal orientations of nano-twinned Ni with void defect at the twin boundaries. The loading angle is defined as the angle between the loading direction and the twin boundary, loading angles of 0, 15, 30, 45, 60, 75, and 90 degrees were investigated in this study. The effects of different loading directions on the mechanical properties and the dislocation glide mechanisms were investigated. The dislocation glide process during the initial stage of plastic deformation for different loading directions was also studied. The results show that the dislocation glide mainly occurs along the {1 1 1} plane that is inclined to the twin boundaries when the loading direction is 0 degrees. The dislocation glide process is constrained by the twin boundaries and, therefore, slips along the twin layers. As the loading angle increases from 0 degrees to 45 degrees, the dislocation gradually shifts and slips along the (1 1 1) slip plane that is parallel to the twin boundaries and twin migration and twinning occur. As the loading angle continues to increase to 90 degrees, the dislocation slips along the {1 1 1} plane again during the loading process. In addition, the dislocation slips toward the adjacent twin layers because they are strongly hindered by the twin boundaries.