The phase diagram of Ti-6Al-4V at high-pressures and high-temperatures. (18th February 2021)

• Record Type: Journal Article
• Authors: MacLeod, S G; Errandonea, D; Cox, G A; Cynn, H; Daisenberger, D; Finnegan, S E; McMahon, M I; Munro, K A; Popescu, C; Storm, C V
• Is Part Of: Journal of physics. Volume 33:Number 15(2021)
• Publication Date: 2021-02-18
• Subjects: Ti-6Al-4V -- x-ray diffraction -- high-pressure -- high-temperature -- phase transformation -- equation-of-state; Condensed matter -- Periodicals; Matière condensée -- Périodiques; Vaste stoffen; Vloeistoffen; Natuurkunde; Electronic journals; Computer network resources; 530.4105
• DOI: 10.1088/1361-648X/abdffa
• Languages: English
• ISSNs: 0953-8984

Abstract

Abstract: We report results from a series of diamond-anvil-cell synchrotron x-ray diffraction and large-volume-press experiments, and calculations, to investigate the phase diagram of commercial polycrystalline high-strength Ti-6Al-4V alloy in pressure–temperature space. Up to ∼30 GPa and 886 K, Ti-6Al-4V is found to be stable in the hexagonal-close-packed, or α phase. The effect of temperature on the volume expansion and compressibility of α –Ti-6Al-4V is modest. The martensitic α → ω (hexagonal) transition occurs at ∼30 GPa, with both phases coexisting until at ∼38–40 GPa the transition to the ω phase is completed. Between 300 K and 844 K the α → ω transition appears to be independent of temperature. ω –Ti-6Al-4V is stable to ∼91 GPa and 844 K, the highest combined pressure and temperature reached in these experiments. Pressure–volume–temperature equations-of-state for the α and ω phases of Ti-6Al-4V are generated and found to be similar to pure Ti. A pronounced hysteresis is observed in the ω –Ti-6Al-4V on decompression, with the hexagonal structure reverting back to the α phase at pressures below ∼9 GPa at room temperature, and at a higher pressure at elevated temperatures. Based on our data, we estimate the Ti-6Al-4V α – β – ω triple point to occur at ∼900 K and 30 GPa, in good agreement with our calculations.