Retardation of creep in 〈001〉-oriented superalloy CMSX-4 single crystals by superimposed cyclic stress

Experimentally it was shown that the cyclic stress superimposed on static load in the case of CMSX-4 single crystals at 800 °C slows down the rate of the creep process. This effect was explained with the help of a recently developed model of creep in 〈001〉-oriented nickel base superalloy single crystals taking into account the interplay of creep in y channels by dislocation slip, dynamic recovery of the dislocation structure and migration of the γ/γ′ interfaces. The simulated creep curves are in reasonable agreement with the experimentally measured ones both for loading with and without the cyclic stress component provided the jog density for creep/cyclic loading is taken to be lower than that for pure creep loading. Thus the retardation of creep by superimposed cyclic loading is attributed to the more difficult formation and/or easier annihilation of jogs on vibrating dislocations.