Design of Ti-Zr-Ta Alloys with Low Elastic Modulus Reinforced by Spinodal Decomposition

Abstract

On the basis of the ternary phase diagram of Ti-Zr-Ta alloys and the d-electron orbital theory, the alloys with the nominal compositions of Ti-40Zr-20Ta (TZT1), Ti-35Zr-20Ta (TZT2) and Ti-30Zr-20Ta (TZT3) (in atom composition) were designed. The alloys were solution-treated (STed) at 1173 K for 3 h, and then aged (Aed) at 973 K for 6 h. The microstructure and mechanical properties of the three alloys were characterized. The results show that the three alloys comprised β-equiaxed grains after solution treatment at 1173 K for 3 h, and the β phases separated into β1/ β2 phases by the spinodal decomposition in the alloys after being aged at 973 K for 6 h. The spinodal decomposition significantly promoted the yield strength of the alloys. For the TZT1 alloy, the yield strength increased from 1191 MPa (in the STed state) to 1580 MPa (in the Aed state), increasing by about 34%. The elastic moduli of the TZT1, TZT2 and TZT3 alloys after solution treatment at 1173 K were 75.0 GPa, 78.2 GPa and 85.8 GPa, respectively. After being aged at 973 K for 6 h, the elastic moduli of the three alloys increased to 81 GPa, 90 GPa and 92 GPa, respectively. Therefore, the spinodal decomposition can significantly promote the strength of the Ti-Zr-Ta alloys without a large increase in their elastic modulus.