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This paper investigated the effect of ruthenium (Ru) addition on the β-phase stability of Ti-Nb alloys containing less than 20 at. % niobium (Nb). The predicted stability of the β-phase was compared with that of known binary Ti-Nb β alloys using the density functional theory (DFT) based CASTEP code. The calculated heats of formation showed that Ru stabilises β-phase. Using the calculated elastic constants, it was deduced that Ti-18Nb-1Ru and Ti-14Nb-2Ru (at. %) have a tetragonal shear modulus less than zero, which indicated that β-phase is stable below room temperature and therefore predicted to exhibit superelasticity that is comparable to that of Ti-(22-24)Nb. Further experimental tests were conducted to verify these predictions. The β-phase structure was predominant, with martensitic (ω and α′′) phases observed in lean Nb alloys. The DSC analysis revealed the ω → β phase transformation, however, the transformation peaks became less intense in Ru-containing alloys compared to Ti-(20-22) Nb alloys. This indicated that Ru is a strong β-stabiliser and it can be used when designing superelastic biomedical alloys with improved corrosion resistance and increased yield strength for orthopaedic applications.

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Effect of Ruthenium on Phase Stability and Superelasticity of Lean TiNb Alloys: Ab-Initio and Experimental Insights

  • 会议论文

  • 发表日期：

    2025年

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  • D. Nkomo,
  • Y. Shen,
  • Y. Yamabe-Mitarai,
  • R. Mostert,
  • M. Phasha

摘要

This paper investigated the effect of ruthenium (Ru) addition on the β-phase stability of Ti-Nb alloys containing less than 20 at. % niobium (Nb). The predicted stability of the β-phase was compared with that of known binary Ti-Nb β alloys using the density functional theory (DFT) based CASTEP code. The calculated heats of formation showed that Ru stabilises β-phase. Using the calculated elastic constants, it was deduced that Ti-18Nb-1Ru and Ti-14Nb-2Ru (at. %) have a tetragonal shear modulus less than zero, which indicated that β-phase is stable below room temperature and therefore predicted to exhibit superelasticity that is comparable to that of Ti-(22-24)Nb. Further experimental tests were conducted to verify these predictions. The β-phase structure was predominant, with martensitic (ω and α′′) phases observed in lean Nb alloys. The DSC analysis revealed the ω → β phase transformation, however, the transformation peaks became less intense in Ru-containing alloys compared to Ti-(20-22) Nb alloys. This indicated that Ru is a strong β-stabiliser and it can be used when designing superelastic biomedical alloys with improved corrosion resistance and increased yield strength for orthopaedic applications.