Effect of Mo Doping Amount on the Mechanical Properties of Ni–Fe Alloy

The effect of Mo alloying on the mechanical performance of Ni–Fe alloys was investigated by first-principles density functional theory calculations within the plane-wave pseudopotential framework as implemented in CASTEP. The elastic constants, elastic moduli, tensile strength, and elastic anisotropy parameters of Mo-doped FeNi3 systems were calculated and analyzed systematically. It was confirmed that all calculated structures accorded with the mechanical stability criteria, indicating their structural stability. Upon the introduction of a single Mo atom, the bulk modulus, Young’s modulus, and shear modulus were all found to increase. Meanwhile, the ideal tensile strength was enhanced to 1.45 GPa. The elastic moduli were decreased with further increase in Mo concentration, suggesting that excessive Mo addition reduces both stiffness and plastic resistance. Among the investigated configurations, both the highest B/G ratio and Poisson’s ratio were achieved in the Mo3FeNi3 system, indicating an improvement of ductility. In addition, with increasing Mo content, the anisotropy indices Aᵁ, Aᴮ, and Aᴳ were progressively reduced, indicating that the introduction of Mo plays a critical role in improving the plastic formability of the material and enhancing the stability of its mechanical properties. These results provide theoretical insights for the optimization of the mechanical performance of Ni–Fe alloys through Mo alloying.