The influence of vacancies diffusion-induced dislocation climb on the creep and plasticity behaviors of nickel-based single crystal superalloy

Abstract

In the nickel-based single crystal superalloys (NBSCSs) that usually works at high temperature, the vacancies diffusion-induced dislocation climb is an important creep/plasticity mechanism besides the dislocation glide. In order to uncover and capture the dislocation dynamics mechanisms behind primary creep and early plasticity of NBSCSs, the glide-only three-dimensional discrete dislocation dynamics (3D-DDD) simulation framework is extended by incorporating the vacancies diffusion-induced climb mechanism. By means of this extended 3D-DDD framework, the climb-assisted dislocation glide in the narrow γ matrix channels of NBSCSs is simulated to study the primary creep and early plasticity behaviors of NBSCSs serving at elevated temperature, with special attention on the important role of dislocation climb in them. The influences of some important factors, such as ambient temperature, applied stress and vacancy supersaturation, which can directly affect the dislocation climb velocity, and the sizes of the two-phase microstructure (i.e., the precipitate size and matrix channel width) on the primary creep of NBSCSs, are studied in detail. In addition, the important role that dislocation climb plays in the early plasticity behaviors of NBSCSs, including the strain rate effect and the tension–compression (T–C) asymmetry, is investigated and discussed carefully. Moreover, some dislocation climb-induced typical dislocation configurations and their dynamics evolutions, including the triangular dislocation loop wrapping around the corner of the precipitate and the dislocation junctions on the {001} γ/γ′ interface, are reproduced, in good agreement with the experimental observation and previous computational simulation published.