Electronic structure mechanism of martensitic phase transformation in binary titanium alloys

Abstract

Influence of alloying elements M (M = Al, Cr, Cu, Fe, Mo, Nb, Ni, Sn, Ta, V, W, and Zr) on phase stability and elastic properties of titanium was studied by first principles total energy calculations. The formation energies of various phases of binary Ti-M alloys are evaluated to identify the influence of alloying elements on phase stability and transformation. The results show a similar dependency of the formation energy on the concentration of alloying elements in various phases: the β, α′, α″, and ω phases. All alloying elements stabilize the β phase and show similar influence of the stabilities of the α′ and α″ phases, but only Al and Sn can increase the stability of the ω phase. The elastic parameters of α″-Ti alloys are also studied in the present work. All alloys have smaller Young's modulus than the pure titanium except the Al and Cu contained alloys, which also show larger bulk and shear moduli than the pure Ti. Elements Cr, Mo, Ni, Sn, Zr, Al, and Cu could stabilize the alloys both energetically and mechanically. Sn and Cr cause the elastic anisotropies, while Zr and Al greatly increase the isotropic properties. The electronic structures are evaluated to study the intrinsic mechanisms of how alloying elements influence the phase stability and transformation and elastic properties of titanium.