The influence of 2 at.% to 4 at.% zirconium on phase equilibria in γ-based Ti–Al alloys

In this work, phase transition temperatures above 1000 °C were evaluated for ternary Ti–Al–Zr alloys containing between 42.5 at.% and 49.5 at.% Al as well as 0 at.% to 8 at.% of Zr. To this end, polarized light microscopy and X-ray diffraction were used on heat-treated and water quenched samples. Furthermore, in-situ information on phase transitions was obtained using differential scanning calorimetry and synchrotron high-energy X-ray diffraction. Mechanical properties of the γ phase subject to added Zr were investigated via nanoindentation on a Ti–46.5Al–4Zr alloy. It was found that the addition of Zr increases eutectoid temperature, narrows the temperature stability range of the α phase and lowers solidus as well as liquidus temperature compared to binary Ti–Al. Oxide scales formed in high temperature air proved to be less adherent with increasing Zr content. The average nanoindentation hardness for the γ phase of Ti–46.5Al–4Zr was 4.3 GPa, the average Young's modulus 165 GPa.