Excellent superplasticity at 800 ℃ achieved via Low-temperature rolling in a novel Ti-44Al-1.5Cr-0.5Re alloy

This study investigates the microstructural evolution and mechanical properties of a novel Ti-44Al-1.5Cr-0.5Re alloy sheet processed by hot rolling at temperatures ranging from 1050°C to 1250°C. Results demonstrate that rolling at 1050°C, near the eutectoid temperature, leads to significant grain refinement with an average grain size of 2.31 μm, attributed to the combined effects of particle-stimulated nucleation (PSN) and α₂ twinning-induced fragmentation. The refined microstructure contributes to exceptional superplasticity at 800°C, exhibiting an elongation of 140% alongside a tensile strength of 472 MPa. Microstructural analysis reveals that the grain refinement mechanism under low-temperature, high-stress rolling involves the decomposition of α₂ and β_o phases into finely dispersed particles, which promote dynamic recrystallization of the γ phase via PSN effect, while repeated α₂ twinning leads to continuous grain subdivision. This work provides a viable low-temperature rolling strategy for producing fine-grained TiAl sheets with excellent superplasticity, offering significant potential for energy-efficient forming of aerospace components.