A molecular dynamic investigation of cyclic strengthening mechanism of Ni-based single crystal superalloy

B Xie and J Wang and YS Fan and RZ Li, MECHANICS OF MATERIALS, 205, 105312 (2025).

DOI: 10.1016/j.mechmat.2025.105312

Ni-based single crystal superalloys, as crucial materials in the aviation and aerospace industry, frequently encounter fatigue failure induced by cyclic loading, which is one of the primary failure modes. In this study, molecular dynamics (MD) simulations are utilized to explore the cyclic strengthening mechanisms of Ni-based single crystal superalloys, with a focus on dislocation evolution under cyclic loading. Two typical feature atomistic models of the alloys are constructed and dislocations are introduced under cyclic loading, investigating the interactions between dislocations and the gamma/gamma ' interface. The results highlight the excellent capacity of the interfacial dislocation network for dislocation deposition, particularly for those attempting to penetrate the gamma ' phase, and capture a transition in emission dislocations slip plane from the 111 plane to the 100 plane. The dislocation absorption is driven by two primary mechanisms: the formation of stable link points at the gamma/gamma ' interface and the obstructive effect of the gamma ' phase. Additionally, a stress stratification phenomenon at the gamma/gamma ' interface is observed, hindering dislocation movement during loading and leading to dislocation trapping through cross-slip during unloading. Furthermore, the simulations reveal two distinct forms of dislocation barriers pile-up within the gamma phase: one arising from the decomposition of the interfacial dislocation network, which leads to the emergence of stacking faults (SFs) bands and Lomer-Cottrell lock; the other stemming from the formation of SFs bands due to the decomposition of the emission dislocations within the gamma phase channel. These findings provide meaningful insights into the cyclic hardening behavior of Ni-based superalloys.

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