基于位错运动的镍基单晶各向异性蠕变寿命预测

The creep tests of three different orientations of the single crystal superalloy DD6 were carried out at 980℃. The results indicate that the creep failure mechanism of superalloy is the initiation of micropores and the propagation of microcracks, which is caused by dislocation motion. The dislocation morphology of monocrystals in [001], [111] and [011] orientation at the initial stage of creep was analyzed by transmission electron microscopy (TEM), matching the characteristics of the octahedral sliding system activated, the hexahedral sliding system activated and the simultaneous motion of the two sliding systems, respectively. Based on the crystal plasticity theory, the creep constitutive model and creep damage model under variational stress conditions considering Orowan effect and dislocation blocking effect were established; meanwhile, the model parameters were fitted according to the creep curve obtained from the test. Moreover, the finite element simulation results of the model and creep fracture morphology of monocrystalline materials confirm each other and explain the anisotropic behavior of monocrystalline creep.