Enthalpies of Solution in Ti–X (X = Mo, Nb, V and W) Alloys from First-Principles Calculations

Abstract

The effects of solute X (Mo, Nb, V and W) on the phase stability of ¢-Ti alloys were studied from first-principles calculations. The firstprinciples calculations yielded solution enthalpies for hexagonal close-packed (hcp)-Ti 35 X 1 and hcp-X 35 Ti 1 and body-centered cubic (bcc)-Ti 26 X 1 and bcc-X 26 Ti 1 solid solution alloys. The enthalpy curves for the ¡ (hcp)-and ¢ (bcc)-phases of TiX alloys were described as a function of the X concentration by using the calculated solution enthalpies and sub-regular solution model. While the enthalpies of the ¡-phases increased with increasing concentrations of Mo, Nb, V and W, the enthalpies of the ¢-phases decreased with increasing concentrations. This is consistent with the experimental results, showing that Mo, Nb, V and W are ¢-stabilizers. The ¢-stabilizing strength of solute elements in Ti alloys is gauged using the experimental critical concentration. We found a good linear correlation between the experimental critical concentration and the theoretical metastable equilibrium concentration at which the enthalpy of the ¡-phase is equal to that of the ¢-phase. The metastable equilibrium concentration decreased with the increasing lattice stability of the bcc structure with reference to hcp structure.

Effect of Alloying Element X on Transformation Strains and Phase Stabilities between α′′ and β Ti-Nb-X (X = Al, Sn, Zr, Ta) Ternary Alloys from First-Principles Calculations

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Recent Topics of Titanium Research and Development in Japan

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Effect of C and Al Elements on High Specific Resistance and High Rigidity of Ultra-High Strength TiC_{(1−<i>X</i>)}/Ti Metal Matrix Composites Fabricated by Blended Elemental Reactive Sintering

“…This research may also change the production design paradigm for titanium-based automotive materials rotating at high speeds. 28)…”