Influence of existence mode of silicide and α2 phase on creep behavior of TC25G alloy at 550−600 °C

In TC25G alloy, Ti 3 Al ( α 2 phase) and silicide were precipitated during long-term aging. To access the effect of precipitates, three heat treatment processes were designed. The effects of these heat treatments on the creep behavior of alloy were compared and analyzed. The results show that the creep resistance of HT2 exceeds that of HT3, highlighting a significant precipitation strengthening effect of α 2 phase. Furthermore, at temperatures and stresses lower than or equal to 570 °C and 200 MPa, respectively, the creep resistance of HT1 is close to that of HT3, suggesting that silicide precipitated before creep attenuates the strengthening of creep deformation caused by the coarsening of α s phase. At 600 °C and 250 MPa, the creep resistance of HT1 is significantly higher than that of HT3, indicating that when the dynamic precipitation of silicide in HT1 is adequate, it also resists the creep deformation of the alloy. The stress exponent for HT1, HT2 and HT3 ranges 1.7−1.9 (550 °C) and 3.7−4.4 (600 °C), indicating that the amount of silicide and α 2 phase doesn’t affect the creep mechanism. The increase in creep activation energy is attributed to the enhanced inhibition caused by lots of precipitates on phase boundary migration and dislocations motion.