A Cr-Mn austenitic steel was tensile strained in the temperature range 273 K (0°) ≤ T ≤ 473 K (200°), to improve the understanding on the role of stacking fault energy (SFE) on the deformation behavior, associated microstructure, and mech. properties of low-SFE alloys.The failed specimens were studied using x-ray diffraction, electron backscatter diffraction, and transmission electron microscopy.The SFE of the steel was estimated to vary between ∼ 10 to 40 mJ/m2 at the lowest and highest deformation temperatures, resp.At the ambient temperatures, the deformation involved martensite transformation (i.e., the TRIP effect), moderate deformation-induced twinning, and extended dislocations with wide stacking faults (SFs).The corresponding SF probability of austenite was very high (∼10-2).Deformation twinning was most prevalent at 323 K (50°), also resulting in the highest uniform elongation at this temperatureAbove 323 K (50°), the TRIP effect was suppressed and the incidence of twinning decreased due to increasing SFE.At elevated temperatures, fine nano-sized SF ribbons were observed and the SF probability decreased by an order (∼10-3).High dislocation densities (∼1015 m-2) in austenite were estimated in the entire deformation temperature range.Dislocations had an increasingly screw character up to 323 K (50°), thereafter becoming mainly edge.The estimated dislocation and twin densities were found to explain approx. the measured flow stress on the basis of the Taylor equation.