Microstructural evolution and sensitization behaviour of thermo-mechanically processed low-nickel high-manganese austenitic stainless steel

Abstract

The present study investigates the effects of cold working (CW) and subsequent thermal ageing (TA) on microstructural evolution and sensitization behaviour of low-nickel high-manganese austenitic stainless steel (NMASS; AISI 201 grade). Two sets of specimens were considered to evaluate the influence of deformation and thermal exposure. In first set, 201-grade NMASS specimens were subjected to 15%, 30% and 50% cold deformation followed by solution annealing. In second set, the cold-worked and solution-annealed specimens were subsequently thermally aged at 700 °C for 30, 60, 120 and 180 min. The specimens were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), while the electrochemical sensitization behaviour was evaluated using double-Loop Electrochemical Potentiokinetic Reactivation (DLEPR) technique. The investigation is aimed at establishing the relationship between the extent of cold deformation, TA, microstructural evolution and sensitization susceptibility of 201-grade NMASS. Particular attention is given to deformation-induced phase evolution and the changes associated with TA that may influence intergranular corrosion (IGC) susceptibility. The DLEPR results likewise varied non-monotonically with deformation and ageing. The maximum reported degree of sensitization (DOS) was 94.45% for 50% cold-worked specimen aged for 60 min, followed by 72.62% and 66.51% after 120 and 180 min, respectively. Post-test morphology indicates that the electrochemical response cannot be interpreted solely as sensitization because attack also occurs within grain interiors in several cold-worked and aged conditions. The results provide a basis for understanding the processing–microstructure–corrosion relationship of NMASS and for identifying processing conditions that can improve its resistance to sensitization in engineering applications.

The authors' abstract, as published at the source. Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications, 2026 · DOI ↗