Tunable the mechanical properties of β-Ti1-xMx binary alloys by transition metal M (M = Fe, Mo, Nb, Ni) substitutional doping: A first-principles study

Abstract

The structural stability, electronic, and mechanical properties of Ti1-xMx (M = Fe, Mo, Nb, Ni) binary alloys were systematically investigated through first-principles calculations based on Density Functional Theory (DFT). The results indicate that the formation energy decreased with an increase in the substitutional atomic M content, accompanied by an increase in the values of C11–C12. This observation suggests a significant improvement in the structural stability of the Ti1-xMx alloys considered, with the concentration of substitutional atomic M ranging from 6.25 % to 50 %. Furthermore, the mechanical parameters, including bulk modulus B and shear modulus G, exhibited a linear increase with the concentration of the alloy element M. The Young's modulus E of Ti1-xFex and Ti1-xNbx alloys increased, whereas Ti1-xMox and Ti1-xNbx alloys reached a minimum value. In addition, the B/G ratio and Poisson's ratio ν indicated that β-Ti1-xMx alloys are fundamentally ductile materials. Moreover, using the stretching model, we demonstrate that the tensile strength of Ti1-xMx alloys was significantly improved by increasing the alloy element M concentration. The enhancement in tensile strength was primarily attributed to the enhanced bond strength between Ti and M atoms, as revealed by the analysis of the density state. These findings provide a pragmatic approach for reinforcing the strength-toughness compatibility of Ti-based alloys, rendering them suitable for aerospace industry applications.