Effect of Solution Process on Microstructure and Properties of Cr-Mn-N Austenitic Stainless Steel

To elucidate the impact of the solid solution process on the microstructure and mechanical properties of Cr-Mn-N austenitic stainless steel, comparative experiments were conducted with varying solid solution temperatures and durations. The results indicate that the grain size gradually increases with increasing solid solution temperature and duration. When the temperature reaches a high level (1120 °C) or is maintained at 1080 °C for an extended period (25 min), the smaller grains are progressively engulfed by the adjacent larger grains, resulting in a swift augmentation in grain size and heterogeneity. In the hot rolled specimens, a considerable quantity of precipitates with large sizes (200 nm) is observed. After the solid solution treatment, the precipitate dimensions are significantly diminished, and their volume fraction is significantly influenced by the temperature of the solid solution. EDS and HRTEM were used to determine that the main precipitated phases after hot rolling and solid solution treatment were Cr₇C₃, Cr₂₃C₆ and Cr₂N. With the increase in the solid solution temperature and time, the increment of grain boundary strengthening and dislocation strengthening decreases, while the contribution of precipitation strengthening initially increases before subsequently decreasing, which is the reason why the experimental steels with solid solution temperature of 1040 °C and solid solution temperature of 1080 °C held at 5 min still have the same mechanical properties despite the difference in solid solution treatment processes.