Superior strength-plasticity integrated TiAl based alloys relying on the dynamic precipitation phase and crystal orientation evolution

The precise control of carbides is key factor in improving service performance of TiAl alloys. We reported a dynamic precipitation strategy that endows TiAl alloys with excellent strength and plasticity. Results show that after doping 0.1 at% C, TiAl matrix is refined, without carbide precipitation, and the relative content of β₀ phase is reduced. After tensile test at 800°C, Ti48Al5Nb2Cr0.6Re alloy exhibits softening characteristics of dynamic recrystallization and planar dislocation-slip, while nano Cr-Re phase and Ti₂AlC particles are precipitated in Ti48Al5Nb2Cr0.6Re0.1C alloy. The γ phase, α₂ phase, and Ti₂AlC particle exhibit specific orientation relationship of (111)_γ // (0001}_α2 // (0001)_Ti2AlC and <110>_γ // <11$\overline{2}$0>_α2 // <10$\overline{1}$0>_Ti2AlC. After tensile test at 900°C, Ti48Al5Nb2Cr0.6Re alloy is in the plastic deformation stage, whereas Ti48Al5Nb2Cr0.6Re0.1C alloy begins to transition from brittle to ductile behavior. High-temperature and stress accelerate the diffusion of C, high-density dislocations and mechanical twinning provide rapid pathways for Ti₂AlC precipitation. Nano precipitates and unique (0001)_Ti2AlC texture evolution retard the softening of Ti48Al5Nb2Cr0.6Re0.1C alloy. As temperature increases from 750 to 900°C, the tensile properties of Ti48Al5Nb2Cr0.6Re alloy decrease from 594MPa and 4.11% to 440MPa and 10.51%, while that of Ti48Al5Nb2Cr0.6Re0.1C alloy first increase from 493MPa and 2.23% to 722MPa and 4.41%, and then stabilize above 520MPa with more than 8% elongation. The improvement in tensile properties is attributed to the reduction of β₀ phase, refinement of microstructure, the interaction between nano Cr-Re phase and dislocations, and the dynamic precipitation of nano Ti₂AlC particles.