Thermo-mechanical creep-fatigue damage evolution and life assessment of TiAl alloy

Thermo -mechanical creep -fatigue (TMCF) behaviors of a TiAl alloy were investigated by conducting various creep, creep -fatigue, and thermo-mechanical tests and performing detailed microstructural analysis. A new creep model was proposed to unify primary strain hardening and tertiary accelerating damage effects. The TMCF failure of TiAl alloys is accompanied by the crack initiation from surface oxides/carbides and mixed transgranular and intergranular cracking. It revealed that introducing thermo-mechanical cycles significantly reduces the creep damage rate during the creep dwell stage and the fatigue process, i.e., the creep -delaying effect, which is attributed to the non -proportional strengthening effect induced by thermal cycles. A life model based on the average minimum creep strain rate was proposed to predict the creep -dominated TMCF life. This model incorporates the complex creep -fatigue interactions on creep damage and demonstrated good agreement with experimental results under varying loading conditions. The present work provides new insights into understanding the creep -dominant thermo-mechanical damage evolution of TiAl alloys.