Effect of hot deformation and heat treatment conditions on the structure and mechanical properties of the VIT1 alloy based on orthorhombic titanium aluminide

The effect of thermo-mechanical treatment on the structure and mechanical properties of the hot-rolled orthorhombic titanium aluminide alloy VIT1 was investigated. The evolution of the microstructure and mechanical behavior of the alloy during hot deformation in the temperature range of 850–1050 °C was studied. It was established that at a temperature of 950 °C, a strain rate of ε· = 5 ·10^–4 s^–1 and a strain of ε = 70 %, the microstructure formed during hot deformation, due to the processes of recrystallization and spheroidization, consisted of grains ~1 μm in size, comprising β-, α₂-, and O-phases. It was shown that increasing the deformation temperature led to the dissolution of O-phase particles and a significant deceleration in the development of dynamic recrystallization. Homogeneous fine-grained billets were obtained via multi-directional isothermal forging, and the effect of heat treatment (quenching and aging) on the structure and mechanical properties of the alloy was examined. Based on a preliminary study of the influence of heating temperature on the alloy’s structure and properties, the temperature ranges for quenching and aging were determined. It was demonstrated that the most balanced levels of strength, ductility, and heat resistance were achieved after heat treatment under the following conditions: holding for 4 h at 1025 °C followed by air cooling, and aging at 850 °C for 6 h.

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