Abstract:The microstructural evolution of NixCryFez alloy during the directional rapid solidification process and the tensile mechanical properties of NixCryFez alloy after solidification were investigated using molecular dynamics simulations. The results reveal that during the solid-liquid phase transition, the temperature initially drops sharply and then rises slightly due to the release of latent heat. During this process, crystal nuclei preferentially form in low-temperature regions, exhibiting heterogeneous solidification characteristics. After solidification, the alloy is primarily composed of face-centered cubic (fcc) structures, with a small amount of hexagonal close-packed (hcp) and body-centered cubic (bcc) structures, and amorphous grain boundaries also occupy a significant proportion. The elemental concentration analysis of the Ni60Cr21Fe19 alloy further indicates that Cr atoms segregate at the grain boundaries. Additionally, a large number of thermally induced twins and stacking faults are formed in the alloy after solidification, with a dislocation density reaching the order of 1016 m–2. The dislocation lines become more concentrated in low-temperature regions, demonstrating significant heterogeneity. The nucleation process of four kinds of Ni-Cr-Fe alloys with different proportions was also studied, revealing that the alloy composition ratio has a significant impact on the nucleation rate. Furthermore, tensile tests were simulated on the Ni60Cr21Fe19 alloy in two directions, showing that the tensile strength perpendicular to the solidification direction is lower than that parallel to the solidification direction due to the anisotropic nature of the directional solidification structure. The discrepancy between the changes in dislocation density and tensile stress-tensile strain indicates that the strengthening mechanism of directional rapid solidification structure of the Ni60Cr21Fe19 alloy is more complex, potentially involving the synergistic effect of multiple strengthening mechanisms.