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利用基于密度泛函理论的第一原理精确Muffin-Tin轨道(EMTO)方法结合相干势近似(CPA), 研究了Ti_1-xV_x与Ti_1-xNb_x合金中α(α'), ω及β相的晶格常数、体模量及相稳定性随成分的变化. 结果表明, Ti-V合金中随着V含量的增加, α(α')相晶格参数a_α$减小, c_α/a_α略有增加, ω相晶格参数a_ω及c_ω/a_ω同时减小, β相晶格参数a_β减小; Ti-Nb合金中随Nb含量的增加, a_α几乎不变, c_α/a_α增加, a_ω增加, c_ω/a_ω减小, a_β几乎不变. 随V及Nb含量的增加, ω与β相的晶格错配度线性增加. V和Nb均能提高三相的体模量, 且增加 β相对于其它两相的稳定性.

Although Ti-V and Ti-Nb binary systems are subjected to many investigations, there remain some issues open for discussion, among which are the lattice parameter misfit and phase boundary between the non-equilibrium ω and β phases. On the other hand, the experimental elastic moduli of the non-equilibrium phases are rarely reported due to the difficulty of the measurement. In this paper, the lattice parameters, bulk moduli and phase stabilities of α(α'), ω, and β phases of binary Ti-V(Nb) alloys are investigated by the use of first-principles exact Muffin-Tin orbital method in combination with coherent potential approximation. It is shown that, with the increase in the V content, the lattice parameter a_α of the α(α') phase decreases, whereas c_α/a_α slightly increases; a_ω and c_ω/a_ω of the ω phase and a_β of the $\beta$ phase decrease. For Ti-Nb alloy, with increasing Nb content, a_α keeps almost unchanged whereas c_α/a_α increases; a_ω increases and c_ω/a_ω deceases; a_β does not change significantly. The lattice parameter misfit between the ω and β phases increases with increasing V or Nb content. Both V and Nb harden the bulk modulus of Ti and improve the phase stability of the β phase relative to the α(α') and ω phases. The theoretical predictions are compared in detail with the available experimental data.