First-principles Calculations of the Elastic Poperties of the Teta-Ti-Nb-Zr Ternary Alloys

In this paper, the elastic moduli of the beta-Ti-Nb-Zr ternary alloys with the nominal composition of Ti24Nb, Ti2ONbl2Zr, Til7Nb21Zr, TillNb38Zr, Ti6Nb53Zr and Ti70Zr were investigated by using first -principles calculation and the experimental measurement. The results show that, with decreasing Nb content, the calculated Young's modulus decreases, however the experimental Young's modulus first decreases and then increases. This difference may be explained by considering the stability of the beta phase; with C' >0, the beta phase is elastically stable and both the calculated and experimental Young's moduli follow the same decreasing trends with Nb content; with C' <0, the beta phase become elastically unstable such that a second phase may precipitate and hardens the alloy. In this case, the calculated Young's modulus is not comparable with the experimental Young's modulus. Therefore the minimum experimental Young's modulus is expected to occur atc'approximate to 1.5 GPa