Creep behavior and microstructure evolution of TiAl alloys synergisticallymicro-alloyed with C and Y2O3 at different temperatures

The microstructure and creep behavior of C/Y 2 O 3 synergistically micro-alloyed high-Al and low-Al TiAl alloys prepared by induction skull melting (ISM) technology were investigated by advanced electron microscopy. Microstructure analysis shows that Y 2 O 3 particles are dispersed in both alloys; element C is dissolved in low-Al alloys as solid solution, while it exists as Ti 2 AlC particles within lamellae in high-Al alloys. Additionally, high-density nanotwins are generated in high-Al alloys. Creep data show that C/Y 2 O 3 micro-alloying significantly enhances creep resistance of TiAl alloys. This benefits from the dispersion strengthening of Y 2 O 3 particles, precipitation hardening of dynamically precipitated Ti 3 AlC particles and lamellar stabilization caused by dissolved C atoms or Ti 2 AlC particles. This strategy causes a more significant improvement on creep resistance of high-Al TiAl alloys, which is attributed to extra twin strengthening effect. At 775-850 °C, these alloys fracture in mixed ductile-brittle mode, but the fracture characteristics change with the increase of temperature.