Assessing the critical role of Re and Co addition in flow stress of Ni-based single-crystal superalloy: A molecular dynamics study

Molecular dynamics simulations are conducted to study the effect of Re and Co addition in the Ni-based single-crystal superalloys on its flow stresses under varying temperature. It is found that Re and Co increase the flow stresses of the superalloys at 100, 300 and 500 K, respectively. The solid solution strengthening mechanism is enhanced with the addition of Re or Co atoms. Moreover, Re or Co promote dislocation nucleation and multiplication and, thus, increase the dislocation density which increases the possibility of forest dislocation interactions. The dislocation proliferation increases additional work hardening capability of the superalloy. At atomic scale, the 1/6<110> stair-rod dislocations were increased by more than 33% (or 11%) for the 2 at.% Re (or Co) systems. Due to the sessile nature of stair-rod dislocation, Re or Co will undeniably affect the mechanic properties of superalloy involving the dislocation mechanisms. For similar concentration of additions, Re is more effective in strengthening the single-crystal superalloys compared with the addition of Co.