Mechanical strain-controlled thermal mechanical fatigue (TMF) tests were performed on thin-walled tubular specimens made of nickel based single crystal superalloy DD6

and the effects of thermal cycles

phase shift and load-controlled mode on stress-strain behavior and fatigue lifetime were studied. The experimental results indicated that the lifetime of TMF was shorter than that of isothermal fatigue (IF) at the peak temperature due to the asymmetry of stress and additional damage induced by thermal cycles. In addition

the lifetime under out-of-phase (OP) cycles was less than that under in-phase (IP) cycles in mechanical strain-controlled mode

which was in contrast with that in stress-controlled mode. According to the results of viscoplastic analysis based on slip systems with Walker constitutive model

the correlation between the damage generated in single crystal superalloy under different TMF loadings and the microscopic parameters on slip systems was identified. Moreover

the max Schmid stress

max slip shear strain rate

cyclic Schmid stress ratio and slip shear strain range were selected as the damage parameters

and then a new life model based on microscopic parameters was proposed for the TMF life prediction. The predicted TMF life of DD6 under different phase shift and different load-controlled mode was within a factor 2 of the experimental life.