Analysis and prediction of non-isothermal creep behavior in Ni-based single crystal superalloy

Non-isothermal creep tests have been performed on single crystal superalloy to investigate the effect of the temperature change on creep behavior. Creep tests were carried out under constant load σ₀ = 300 MPa using a changing temperature route: 980 °C–1050 °C–980 °C. The pre-creep time is designed as 5 h, 10 h and 15 h. The non-isothermal temperature is set at 1050 °C and maintains 30 min. The results show that longer pre-creep time t_pre generates larger strain rate after temperature change, therefore, the creep life is shorter. Moreover, creep strain jump can be observed with the rise of temperature, a new primary and secondary stage can be found. In view of these phenomena, this paper pays remarkable attention on the evolution of the microstructure at the positions where the temperature changes. To predict the non-isothermal creep behavior, a modified crystal plasticity model was proposed by adding physically motivated internal variables, e.g. dislocation density and matrix channel width. The non-isothermal creep behavior predicted by finite element calculation was in a good agreement with the experimental results.