Cryogenic temperature stacking fault energy control and deformation mechanism of high-Mn austenitic steel

This study systematically investigated the regulation mechanism of cryogenic temperature stacking fault energy (SFE) in high-Mn austenitic steel and its influence on deformation behavior. By constructing an improved thermodynamic model, the multiple coupling effects of manganese content (15-35 wt.%), temperature (4.2 K-293 K), and grain size (≤35 μm) on SFE were analyzed. The results show that the SFE increases nonlinearly with increasing Mn content, and this trend is significantly weakened by decreasing temperature; while grain refinement can effectively compensate for the decrease in SFE caused by low temperature. Calculations of the contribution ratios of the strengthening confirmed that the deformation mechanism of Fe-0.45C-24.4Mn high-Mn steel changes with temperature gradient. At 293 K (SFE=34.55 mJ/m²), dislocation slip is dominant, while at 77 K (SFE=24.22 mJ/m²) and 4.2 K (SFE=20.20 mJ/m²), twinning becomes the dominant mechanism. Meanwhile, the study further proposed a threshold criterion for cryogenic temperature SFE (the critical value for TWIP/TRIP transition is 15 mJ/m² at 77 K, and further reduced to 12 mJ/m² at 4.2 K), providing theoretical support for the design of low-cost, high-performance cryogenic temperature storage and transportation materials.