Evolution of fatigue mechanical properties and micro defects in nickel-based single crystal superalloys: A molecular dynamics research

Cyclic loading is the main contributor to fatigue failures in mechanical components. In this paper, the fatigue deformation behavior of nickel-based single crystal superalloys was investigated through molecular dynamics methods. It was found that the fatigue process can be divided into the hardening stage and the saturation stage. The stress amplitude, dislocation density and number of planar faults fluctuated before the saturation stage, but they were relatively stable in the saturation stage. The Perfect dislocations at the interface decomposed into Shockley dislocations with temperature increase before fatigue. The decomposition process became more dramatic as fatigue began. As the fatigue continued, the extended dislocations in the Ni phase gradually got rid of the Ni/Ni₃Al interface and sheared the Ni₃Al phase, leading to the generation of antiphase boundaries. The extended dislocation moved reciprocally when the fatigue reached the saturation stage. The difference was that the extended dislocations crossed the interface at 300 K but not at other temperatures.