Incipient plasticity and dislocation loop evolution in rock-salt vanadium nitride

摘要

Incipient plasticity and dislocation loop (DL) evolution are two important plastic behaviors of ceramic materials. In this work, we performed molecular dynamics simulations of the nanoindentation on vanadium nitride (VN) surfaces with different Miller indexes to investigate the incipient plasticity, dislocation reactions, and the evolution of the DLs. It was found that the plasticity of VN proceeds by the nucleation and glide of partial dislocations, forming {111} stacking fault (SF). However, dislocation patterns of nanoindentation along different crystallographic orientations are quite different, which to be specific are dislocation flower for {001}, SF tri-pyramid for {111}, and symmetric inclined SF for {110} indentions. There are two kinds of reactions between the primary defects, including the movement of two parallel partial dislocations forming an extended dislocation, and the intersection of two unparallel SFs forming a stair-rod dislocation. The Thompson tetrahedron was extended to the illustration of the evolution of the microstructures in B1 crystalline VN during the nano-indentations on differently oriented surfaces.