Atomistic Investigation on the Strengthening Mechanism of Single Crystal Ni-Based Superalloy under Complex Stress States

Single crystal Ni-based superalloy, with excellent mechanical properties in high temperature, always works under complex stress states, including multiaxial tension and compression, which results in various strengthening mechanisms. In this paper, the atomistic simulation is applied to investigate the microstructure evolution under complex mechanical loading conditions, including uniaxial, equibiaxial, and non-equibiaxial tensile–compressive loadings. By comparison of the strain–stress curves and analysis of dislocation motion, it is believed that the tension promotes the bowing out of dislocations into the channel at loading direction, while compression limits it. Moreover, the dislocation analysis shows that the initial dislocation network, comprised of Lomer dislocations, will dissociate to form Lomer–Cottrell lock upon loading, which acts as a barrier to the further glide of dislocations. The mechanism of dislocation evolution is analyzed in detail by combining Schmid factor analysis and the comparison of energy density difference between γ and γ′ phases