An atomic scale insight into a new twinning deformation mode in γ'-Ni3Al phases

Micro-twinning is an important creep mode of γ'-Ni 3 Al phases in Ni-based single crystal superalloys at intermediate temperature and low stress. On the basis of the experimental observation of superlattice intrinsic stacking faults (SISFs) generated by a sequential shear of 1 / 2 110 full dislocation and 1 / 6 112 Shockley partial at low temperature and high stress, a new twinning mechanism deferent from previous true-twinning and pseudo-twinning modes is proposed. An atomic scale comparison reveals this new-twinning is more favorable than the true-twinning in energetics, although it is not as feasible as the pseudo-twinning. And, unlike the pseudo-twinning deformation requested for temperature-dependent atom reordering, a stable micro-twin can be directly created by a continuous glide of 1 / 2 110 dislocation pairs in the new twinning deformation. It is speculated this new twinning can be initiated at low temperature and intermediate stress owing to its moderate activation energy and no requirement for atom reordering.