Effects of heat shock at 800 °c on mechanical properties of γ-TiAl alloys

Effect of heat shock on the mechanical properties and the microstructure of TiAl alloys (Ti-47Al-2Cr-2Nb and Ti-45.3Al-2Cr-2Nb-0.1W-0.15B) with near fully lamellar structure were investigated. After heat shock process from room temperature to 800 °C for 500 cycles, the microstructure demonstrated that lamellar microstructure has been destructed by the presentation of some γ and α₂ block phases in lamellar structure, resulting in the ductility of as-polished Ti-47Al-2Cr-2Nb alloy decreased by about 70% and the ultimate tensile strength (UTS) reduced by about 25%, and the ductility of as-unpolished Ti-47Al-2Cr-2Nb alloy decreased by more than 70% and the ultimate tensile strength (UTS) was reduced by about 35%. The ductility of Ti-45.3Al-2Cr-2Nb-0.1W-0.15B alloy decreased by about 60% and the ultimate tensile strength (UTS) reduced by about 18% after heat shock, which was resulted from the appearance of small α₂ block phase at interfaces of lamellar colonies and microcracks at the interfaces of ribbon boride and lamellar structure.