Microstructural evolution and mechanical property improvement of TiAl alloy during powder forging

A novel powder forging method that integrates the advantages of powder metallurgy and forging is proposed. TiAl prealloyed powder and binder were cold pressed, followed by pressureless sintering and subsequent forging to achieve densification. Results show that sintering necks formed between powder particles after pressureless sintering by diffusion. During forging, the lamellar colonies were broken and preferentially recrystallized at the sintering neck. The forged microstructure consisted of bent lamellar colonies oriented perpendicular to the forging direction, accompanied by refined equiaxed γ grains. In the range of 1320 °C–1400 °C, as the forging temperature increased, the recrystallization rate accelerated, leading to the disappearance of the deformed structure. The deformed microstructure is meticulously developed, featuring a high density of dislocations and twins, which significantly contribute to the enhancement of the mechanical properties of the TiAl alloy. After forging at 1360 °C for 10 min, the material achieved optimal ultimate tensile strength, with values of 818 MPa at room temperature and 489 MPa at 900 °C.