Molecular dynamics study on the effect of Ni atoms on the crack arrest performance of Fe–Ni alloy

Molecular dynamic simulations are applied to test the nickel's modification mechanism of Fe–Ni alloy. Mono displacement loading is applied to a perfect single crystal model, a single crystal model with vacancies, and a model with transgranular crack. Moreover, constant strain load is applied to the polycrystal model to test the Ni effect on intergranular crack initiation. The results elucidate that Ni atoms could decrease the free surface energy and the stacking fault energy simultaneously. However, Ni atoms have a more significant effect on the reduction of stacking fault energy. If the Ni concentration is above 0.03, the transgranular crack constantly emits dislocations under loading, thus, postponing the cleavage cracking. Particularly, as the Ni concentration is above 0.05, the recrystallization process could be a favorable energy‐releasing behavior compared with the intergranular cracking. The findings suggest that a low concentration of Ni might degrade the physical property of Fe–Ni alloy. Increasing the Ni atomic concentration above specific critical values, for example, 0.03 or 0.05, could enhance the fracture toughness.