Atomic simulations of crack propagation in Ni-Al binary single crystal superalloy with a central crack

L Yang and HC Dong and DY Wu and HK Ma and ZH Feng and P He and B Narayanaswamy and BC You and Q Wang and R Su, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, 302, 113006 (2024).

DOI: 10.1016/j.ijsolstr.2024.113006

Nickel (Ni)-based single-crystal superalloys are of great importance in the aircraft industry due to their excellent mechanical properties, and cracks as unavoidable defects may affect the mechanical performances of materials dramatically. In this paper, large scale molecular dynamics (MD) simulations are carried out to understand the deformation mechanisms of Ni-based single crystal with a central crack under tension. Here, the effects of matrixes (gamma, gamma ' and gamma/gamma '), strain rates (1 x 10(9) s(- 1) similar to 3 x 10(9) s(-1)) and temperatures (300 K similar to 900 K) on the role of crack propagation are considered. It is observed that dislocations and slip systems in the gamma ' model are concentrated near the crack, resulting in the rapid expansion of dislocation, which leads to the fastest crack growth speed and early fracture. While the crack propagation rate of gamma and gamma/gamma ' models are relatively slow, due to the combined action of the Lomer-Cottrell lock and stacking fault tetrahedron structure and Stair-rod dislocation, which hinders crack propagation. In addition, deformation at increased strain rates and/or reduced temperatures, lead to superior yield stress and Young ' s modulus for models with a central crack at gamma/gamma ' interface. On the other hand, high temperature and high strain rate will promote crack propagation in the gamma phase, and the higher the strain rate and/or temperature, the faster the crack propagation speed will be. These results will enrich our understanding on the crack propagation and evolution mechanisms in Ni-based single crystal superalloy.

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