A Cr-Mn austenitic steel was tensile strained at 273 to 473K in order to improve the understanding of the role of stacking-fault energy in the deformation behavior, associated microstructure and mechanical properties of low stacking-fault energy alloys. Failed specimens were studied using X-ray diffraction, electron back-scattering diffraction and transmission electron microscopy. The stacking-fault energy of the steel was estimated to vary between about 10 and 40mJ/m2 at the lowest and highest deformation temperatures, respectively. At ambient temperatures, the deformation involved martensite transformation (TRIP effect), moderate deformation-induced twinning and extended dislocations with wide stacking faults. The corresponding stacking-fault probability of austenite was very high (0.01). Deformation twinning was most prevalent at 323K, resulting in the highest uniform elongation at this temperature. Above 323K, the TRIP effect was suppressed and the incidence of twinning decreased due to increasing stacking-fault energy. At elevated temperatures, fine nano-size stacking-fault ribbons were observed and the stacking-fault probability decreased to 0.001. High dislocation densities (1015/m2) in austenite were estimated over the entire deformation temperature range. Dislocations had an increasingly screw character up to 323K, and were then become mainly edge. The estimated dislocation and twin densities approximately explained the measured flow stress, on the basis of the Taylor equation.

A Stacking Fault Energy Perspective into the Uniaxial Tensile Deformation Behavior and Microstructure of a Cr-Mn Austenitic Steel. H.Barman, A.S.Hamada, T.Sahu, B.Mahato, J.Talonen, S.K.Shee, P.Sahu, D.A.Porter, L.P.Karjalainen: Metallurgical and Materials Transactions A, 2014, 45[4], 1937-52