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

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.