On the Stacking Fault Energy Evaluation and Deformation Mechanism of Sanicro-28 Super-Austenitic Stainless Steel

In the present study, the reliance of deformation mechanism of a super-austenitic steel (Sanicro-28) on the external stress and stacking fault energy (SFE) was quantitatively investigated by analyzing the stacking fault separation. The stacking fault energy of the experimental alloy was determined using line profile analysis through x-ray diffraction measurements. Considering the calculated SFE and external stress, the predominant deformation mechanism was predicted by a quantitative model. A set of experimental examinations were carried out validating the applied model. The experimental findings reveal that the plasticity mechanism of steel can be divided into two stages. In the first stage (at lower strain), no mechanical twin was observed in the microstructure and the dislocation glide would control the plasticity. In the second stage (at higher strain), the mechanical twinning was considered as the predominant plasticity mechanism. Furthermore, regarding the stress threshold of mechanical twin formation, as the SFE increases, the critical stress for mechanical twinning initiation intensifies. However, in the present super-austenitic stainless steel, the mechanical twinning was observed at the stresses lower than those predicted by the applied model. This was related to the various interactions between dislocation and different barriers in the solid solution matrix.