TY - JOUR

T1 - The effect of zirconium on the Ti-(42-46 at.%)Al system

AU - Musi, Michael

AU - Kardos, Stefan

AU - Hatzenbichler, Lukas

AU - Holec, David

AU - Stark, Andreas

AU - Allen, Melissa

AU - Güther, Volker

AU - Clemens, Helmut

AU - Spörk-Erdely, Petra

PY - 2022/10/2

Y1 - 2022/10/2

N2 - In recent years, Zr has emerged as a promising alloying element for intermetallic γ-TiAl based alloys to improve their mechanical properties. The present work focuses on the influence of this element on the microstructure and the thermodynamic phase equilibria in the ternary Ti-(42-46)Al-(2-4)Zr (at.%) system. Alloying with Zr was found to increase the amount of the γ phase in the microstructure of cast material densified by hot-isostatic pressing. Simultaneously, the material's hardness increased due to solid solution strengthening as well as the refinement of lamellae in the α2/γ colonies. With respect to the phase transformation behaviour, a significant decrease of the solidus temperature was observed in the high Zr alloyed material variants. In combination with the stabilization of the γ phase, this essentially results in a narrowing of the single α phase field region in the Ti-Al-Zr phase diagram derived in this work. In situ high-energy X-ray diffraction was performed on Ti-46Al-2Zr and Ti-46Al-4Zr (at.%) specimens to investigate the phase transitions above and below the solidus temperature by utilizing two different experimental setups. These experiments showed that upon heating, small amounts of β phase are formed in both alloys prior to the transition into the peritectic α+β+L phase field region. Furthermore, an additional heat treatment study was conducted to determine the influence of Zr and temperature on the resulting microstructure. The combination of X-ray diffraction techniques with ab-initio calculations revealed a significant asymmetric influence of Zr on the lattice parameter of the γ phase, resulting in a decreasing c/a ratio.

AB - In recent years, Zr has emerged as a promising alloying element for intermetallic γ-TiAl based alloys to improve their mechanical properties. The present work focuses on the influence of this element on the microstructure and the thermodynamic phase equilibria in the ternary Ti-(42-46)Al-(2-4)Zr (at.%) system. Alloying with Zr was found to increase the amount of the γ phase in the microstructure of cast material densified by hot-isostatic pressing. Simultaneously, the material's hardness increased due to solid solution strengthening as well as the refinement of lamellae in the α2/γ colonies. With respect to the phase transformation behaviour, a significant decrease of the solidus temperature was observed in the high Zr alloyed material variants. In combination with the stabilization of the γ phase, this essentially results in a narrowing of the single α phase field region in the Ti-Al-Zr phase diagram derived in this work. In situ high-energy X-ray diffraction was performed on Ti-46Al-2Zr and Ti-46Al-4Zr (at.%) specimens to investigate the phase transitions above and below the solidus temperature by utilizing two different experimental setups. These experiments showed that upon heating, small amounts of β phase are formed in both alloys prior to the transition into the peritectic α+β+L phase field region. Furthermore, an additional heat treatment study was conducted to determine the influence of Zr and temperature on the resulting microstructure. The combination of X-ray diffraction techniques with ab-initio calculations revealed a significant asymmetric influence of Zr on the lattice parameter of the γ phase, resulting in a decreasing c/a ratio.

U2 - 10.1016/j.actamat.2022.118414

DO - 10.1016/j.actamat.2022.118414

M3 - Article

VL - 241.2022

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

IS - December

M1 - 118414

ER -