Nanomechanical insights into the deformation behavior of austenitic alloys with different stacking fault energies and austenitic stability

Highlights: → Deformation mechanisms of Type 316L, 301LN, and TWIP steels were elucidated. → Nanoindentation and electron microscopy was used to explain deformation behavior. → Multiple pop-ins depend on the stability and stacking fault energy of the steels. → Strain-induced martensite formation and twinning involve variant selection. - Abstract: Nanoscale experiments and electron microscopy were combined to probe the deformation behavior in near defect-free volume of three austenitic steels (Type 316L, 301LN, and TWIP steel) with different stacking fault energies and austenite stability. In all the three steels, the occurrence of first pop-in is related to nucleation of dislocations in the small defect-free volume. But the second and subsequent pop-ins describe the load-displacement response resulting from the multiplication, motion and pile-up of dislocations and twinning in stable 316L stainless steel, phase transition such as strain-induced austenite-to-martensite phase transformation in metastable 301LN steel, and twinning in TWIP steel. Pop-ins associated with deformation twinning occur at a lower displacement in TWIP steel as compared to 316L steel, consistent with the lower stacking fault energy of TWIP steel. Both strain-induced martensite formation and twinning involve variant selection.