Microstructures observation and hot compressing tests of TiAl based alloy containing high Nb

Ti-Al based alloys containing high Nb are currently under extensive attention because Nb is the most effective element improving their mechanical properties at high temperature (HT). However, high Nb addition might generate the third phase, degrading their mechanical properties, which can keep α₂+B₂+γ ternary phases existing. A new Ti-Al based alloy with high Nb content, whose nominal chemical composition is Ti-45Al-8.5Nb-0.3W-0.05Y at.%, was developed through hot compressing tests. The results show that the alloy with near fully lamellae (NFL) microstructure has higher ultimate compressing strength (σ_p) and 0.2% proof strength (σ_0.2) than those with Duplex (DP) microstructure at HT, but maximum compressing rate (Δl/l) inversely The combination of Nb atom solid solution strengthening and yttrium oxide precipitation strengthening contribute to their HT strength, refine grains bring the better plasticity. Simultaneously, the microstructure evolution was observed using light microscope (LM) and transmission electron microscope (TEM) after thermo-mechanical process, such as lots of stacking faults, twins, and jog of stacking faults and twins, which result from the coordination of deformation.