Effects of crystallographic orientation, temperature and void on tensile mechanical properties of Ni-Co single crystal nanopillars

Abstract

In this present contribution, molecular dynamics simulation was performed to investigate the tensile response and deformation mechanism under different influencing factors, such as Co content, crystallographic orientation, rate, temperature and void. It is concluded that the number of stair-rod dislocation is the maximum during the deformation process of single crystal nanopillars with the Co content of 10%. It is interesting that the aggregation formed by five stacking fault tetrahedron, whose edge is composed of stair-dislocation formed by the combination of the stacking fault and another incomplete dislocation, is present, responsible for the rise of stress in the plastic deformation curve (0.1 < ε < 0.13). When loading in the [111] direction, the dislocation density keeps a relatively high level compared to the other two directions. In addition, the prismatic dislocation loops are formed by the interaction, reaction and separation of Shockley, stair-rod dislocations by the intersection of the slip planes at an acute angle and Hirth dislocations at an obtuse angle at 50 K, having a fixed effect on the dislocation, which also leads to the increase of strength. The presence of the smaller void volume is conducive to the nucleation and expansion of dislocations, yet when the void volume is too large, the failure process is not dominated by dislocation but by stress concentration at the voids. The above results are beneficial to explore and design of this fascinating single crystal alloy in the fields involving aerospace and electronic power.