The role of anelastic recovery in the creep-fatigue interaction of 9-12% Cr steel at high temperature

Fatigue tests of 9-12% Cr ferrite steel with various hold times at both peak and valley points were conducted under stress control at 898 K. The role of anelastic recovery in the creep-fatigue interaction was discussed systematically. Results indicate that anelastic strain increases primarily with the cycle increase and then decreases slowly until the specimen failed during the unloading process. By contrast, the kinetics of anelastic recovery decreases during the unloading process while is insensitive to the peak stress and hold time at the early stage. In addition, the creep-fatigue (cyclic creep) interaction is much decelerated due to the anelastic recovery compared to the static creep state. A modified life prediction model is developed accordingly under the frame of ductility exhaustion concept by incorporating the effect of anelastic recovery. A good agreement with the experimental data is achieved and thus provides us confidence in the use of the modified model in practice.