First-Principles Study of Structural Stability and Tensile Strengths of Light-Element-Doped ZrTi

ZrTi alloys have potential applications in critical parts of spacecraft. As lightweight design is a fundamental requirement for spacecraft, incorporating light elements into ZrTi alloys is a feasible approach. In this paper, we investigated the tensile deformation behavior of ZrTi doped with light element by using the plane-wave pseudopotential density functional method. Covalent Ti–Zr bonds accommodate deformation by softening and breaking at large tensions, and structural stability of ZrTi and ZrTiX (X = B, Al, Ga, and V) is determined by the strength of these Ti–Zr bonds under tension. The results show that the lower doped concentrations of light element decrease the tensile strengths. However, there is no obvious difference in tensile strengths along [11 \(\bar {2}\) 0] direction between ZrTi and ZrTi_0.875Al_0.125. The results of Mulliken overlap populations indicate that different tensile strengths of ZrTiX should be resulted from different strengths of covalent Ti–Zr bonds. The incorporation of light element dopants does not strengthen all chemical bonds and weakens strengths of covalent Ti–Zr bonds, indicating that experimental strengthening mechanism of ternary ZrTiX alloys could be ascribed to Hall–Petch effect.