Interfacial dislocation evolution and yield mechanism of nickel-based single crystal superalloy: A molecular dynamics research

The evolution models of interfacial dislocation and yield mechanism are critical for the mechanical properties of nickel-based single crystal superalloy. In this paper, the deformation process of nickel-based single crystal su-peralloy was investigated through molecular dynamics methods. It was found that the interfacial dislocations decomposed and formed a special "cone-like" microstructural defect under uniaxial compressive loading, but this special structure would disappear with the increase in temperature. The special structure can significantly improve the yield strength due to its strong ability to hinder the slipping of dislocations. The yield mechanism is the decomposition of sessile dislocations and the shearing of the gamma' phase by the Shockley dislocation for uniaxial compressive loading. In contrast, the yield mechanism is the shearing of the gamma' phase by extended dislocation and the generation of antiphase boundary for uniaxial tensile loading. Although the temperature did not affect the yield mechanism, it could influence the yield strength by changing the dislocation density. Moreover, both the evolution models of interfacial dislocation and the yield mechanism exhibited tension-compression asymmetry, which eventually led to the tension-compression asymmetry of mechanical properties.