Exploring the effects of the sheared voids on the hardening of tungsten using atomistic simulations

Abstract

Understanding atomic-scale mechanisms of dislocation interacting with irradiation-induced nanosized voids is vital to predict in-service performances of nuclear components. In reality, multiple dislocations can sequentially interact with one void, namely, the already sheared void can be further sheared by incoming dislocations; however, previous work mostly focused on the first-time dislocation-void interaction and assumed that already sheared voids have the same hardening effects in subsequent interactions. Using atomistic simulations, this work studies the interaction mechanisms between a periodic array of voids and successively incoming edge dislocations, and corresponding hardening effects. Simulation results reveal that the sheared voids impede dislocation motion in the same manner as the unsheared ones do, but the resistance to dislocation glide could decrease with interaction times. As an edge dislocation is pinned by the void, a pair of screw dipole form on the dislocation. Then the screw arms move along the void surface through multiple-time cross-slip upon continuous shear deformation, until the dipole annihilate in or above the original slip plane at some critical stress, thereby releasing the dislocation. These atomic processes are also accompanied with absorbing vacancies from the void and climbing up of dislocation segment in each interaction event. Hardening effect of the sheared voids can be progressively weakened due to decreasing void size when interaction times exceeding some value. The hardening effects of sheared voids can be quantified by a modified Bacon-Kocks-Scttergood model, if adopting an effective diameter that is calculated from the major axis of the dislocation-void intersection region rather than the constant diameter of the unsheared void.