Microstructural characterization of creep cavitation in a fully-lamellar TiAl alloy

摘要

Ti-46.5Al-2Cr-3Nb-0.2W with a fully-lamellar microstructure was crept under 1073 K, 270 MPa. Creep fracture is due to cavitation on grain boundaries. Cavity nucleation follows two mechanisms: dynamic recrystallization mechanism and interlocked mechanism. The two mechanisms suggest that, different from in polycrystalline materials, in fully-lamellar materials the difference of grain orientation determines the cavity nucleation at grain boundaries. Cavity shape and experimental data of cavity growth rate are in agreement with quasi-equilibrium growth theory, so proper alloy-doping and heat treatment can improve creep resistance by reducing diffusive conductance of the grain boundary.