The deformation behavior of a high-Mn austenitic steel was investigated using in-situ straining transmission electron microscopy (TEM), with emphasis on the dynamic interaction between stacking faults and partial dislocations during plastic deformation. Owing to the low stacking-fault energy of the alloy, plastic deformation is primarily governed by Shockley partial dislocations, leading to extensive stacking-fault formation on multiple 111 planes. As deformation proceeds, stacking faults generated on different slip variants frequently intersect within grain interiors. Real-time observations reveal that these intersections act as strong deformation-induced barriers that impede partial dislocation motion, resulting in dislocation pile-up and localized strain concentration. Such interactions are considered to contribute significantly to strain hardening in low stacking-fault energy austenitic alloys. Despite their strong blocking effect, stacking-fault intersections are not strictly impenetrable. Under conditions of significant dislocation accumulation, the separation distance between leading and trailing partial dislocations can locally decrease, allowing temporary recombination into a perfect dislocation segment. The recombined dislocation adopts screw character, enabling cross-slip onto a secondary 111 slip plane, followed by re-dissociation into Shockley partial dislocations. These findings demonstrate that stacking-fault intersections function as dynamic microstructural features that both impede and mediate dislocation motion. The present in-situ TEM observations provide direct mechanistic insight into stacking-fault intersection-controlled dislocation dynamics and their role in strain hardening and local plastic accommodation in low stacking-fault energy austenitic steels.
S I Kim (Thu,) studied this question.