In-situ TEM Investigation of Stacking-Fault Intersection–Controlled Deformation in High-Mn TRIP Steel

The deformation behavior of a high-manganese transformation-induced plasticity (TRIP) 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 dominated 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 demonstrate that these intersections act as strong deformation-generated barriers that impede partial dislocation motion. The resulting dislocation pile-up and local strain concentration contribute significantly to the pronounced work-hardening capability of the TRIP steel. Despite this strong blocking effect, detailed in-situ analysis reveals that 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 their temporary recombination into a perfect dislocation segment. The recombined dislocation assumes screw character, which enables cross-slip onto a secondary {111} slip plane. After cross-slip, the perfect dislocation can redissociate into Shockley partial dislocations due to the low stacking-fault energy of the alloy, allowing glide to resume on the new slip plane. These observations demonstrate that stacking-fault intersections primarily function as strengthening barriers to partial dislocation motion, while occasionally enabling stress-assisted dislocation recombination and localized cross-slip. The present in-situ TEM results provide direct mechanistic insight into the dynamic interaction between stacking faults and dislocations and clarify how stacking-fault intersections influence both strain hardening and local plastic accommodation in high-Mn TRIP steels.