Insight in the impact of pre-deformation on structure - deformation - property relationship in Cr-Mn-N stainless steel

The present study aimed to investigate the impact of pre-deformation on the structure-deformation-property relationship in Cr-Mn-N austenitic stainless steel (ASS). The commercial Cr-Mn-N ASS was cold-rolled (CR) at room temperature with a thickness reduction from 5% to 60%, whose microstructural characteristics were identified by optical microscopy, scanning and transmission electron microscopy, and electron backscatter diffraction together with X-ray diffraction. The results indicated that the microstructure varied from equiaxed austenite in the as-received specimen to the coexistence of stacking faults (SFs), deformation twins (DTs) and strain-induced martensite (SIM) in pre-deformed specimens. Furthermore, detailed TEM results showed that equiaxed dislocation cells, DT nets and dislocation-cell-type α'-M occurred in the 60% CR specimen. Tensile tests revealed that the strength of ASS increased while the plasticity decreased with the increase of pre-reduction deformation. Such mechanical properties were confirmed to be related to the variations in microstructure-dependent deformation mechanisms, varying from planar slip + DTs + SIM in the as-received specimen, to DTs + SIM with 30% reduction, and SIM + minor twinning with 60% reduction, respectively, in the pre-deformed specimens.