Influence of kinetic effect on interaction between edge dislocation and irradiated dislocation loops in BCC Tantalum

Abstract

In this paper, the interaction between an edge dislocation and irradiation <100> sessile self-interstitial atom (SIA) type dislocation loops (DLs) is studied by atomistic simulations in BCC Ta at 0 and 300 K. Both molecular dynamics (MD) and statics (MS) simulations are performed to highlight the dislocation kinetic effect (or dynamic effect) on the critical resolved shear stress (CRSS) for dislocation bypassing the DLs and on the dislocation-SIA DLs interaction mechanisms. The simulation results show that the dislocation-DLs interaction mechanisms are two-fold. When the DL size is lower than a critical value, the moving edge dislocation tends to completely absorb the DLs or fully transform the original DLs into other-type ones. However, when the DL size is higher than the critical value, the moving dislocation tends to absorb or transform the DLs partially or even marginally. Moreover, with increasing applied shear stress, the high-speed dislocation has no sufficient time to absorb SIAs from DLs, which also changes the dislocation-DLs interaction process remarkably. When the dislocation is accelerated to subsonic, an abnormal “pull forward” dislocation configuration may present upon the dislocation bypasses a small DL. More importantly, with the kinetic effect considered, the CRSS for dislocation overcoming the barriers of DLs decreases significantly for the dislocation-DLs interaction mechanisms. In order to appropriately describe the kinetic effect on the CRSS, amended dispersed barrier hardening (DBH) and Bacon-Kocks-Scattergood (BKS) hardening models for the latter dislocation-DLs interaction mechanism are proposed.