The microstructure and tensile property degradation of a gamma-TiAl alloy during isothermal and cyclic high temperature exposures

The microstructure and tensile property changes of a γTiAl-based alloy, Ti-47Al-2Cr-2Nb-0.15B, during isothermal and cyclic high temperature exposures have been investigated. Microstructure coarsening, including the fracture, dissolution and spheroidization of α2 lamellae, is considered to be the main cause of the evident tensile property decreases of the alloy after isothermal and cyclic high temperature exposures. Dislocation emission near the broken lamellae is also an important phenomenon in the microstructure degradation during cyclic high temperature exposure, which originated from the thermal mismatch between α2 and γ phases.

Microstructure coarsening, which is characterized by broken α2 platelets, crooked lamellar interfaces and perpendicular decomposition of α2 platelets, is considered to be the main cause of the evident tensile property decreases of Ti-47Al-2Cr-2Nb-0.15B alloy after isothermal and cyclic high temperature exposures. Dislocation emission near the broken lamellae is also an important phenomenon in the microstructure degradation during cyclic high temperature exposure, which originated from the thermal mismatch between α2 and γ phases .Figure optionsDownload as PowerPoint slideResearch highlights
► Lamellar fracture and spheroidization happened during high temperature exposures.
► Dislocation emission caused by thermal mismatch also appeared.
► Microstructure coarsening is the main cause of the tensile property reduction.
► Cyclic high temperature exposure induces more severe degradation.