Influence of refined hierarchical martensitic microstructures on yield strength and impact toughness of ultra-high strength stainless steel

Haiwen Luo, Xiaohui Wang, Zhenbao Liu, Zhiyong Yang

Table 1 The hierarchical martensitic microstructural features, including the average sizes of prior austenite grains (da), martensite packets (dp)/blocks (db)/laths (dl) and the aspect ratio of martensite lath, and mechanical properties, including both Charpy U-Notch impact toughness (CUN) and yield strength (0.2 % offset proof stress, YS), were all measured on UHSSS specimens subjected to four different manufacturing processes

Sample No. Hot rolling Process da/μm dp/μm db/μm dl/μm Aspect ratio CUN/J YS /MPa HR75 75% reduction and finished at 1050?°C 6.3?±?3.7 2.8?±?1.1 2.1?±?1.0 0.24?±?0.11 11.6 186?±?3 1065?±?4 HR50 50% reduction and finished at 1050?°C 14.5?±?8.8 6.3?±?2.7 2.1?±?0.9 0.26?±?0.12 24.2 193?±?3 1035?±?2 HR50-2 50% reduction and finished at 1080?°C 16.1?±?9.1 6.7?±?2.2 2.2?±?0.9 0.25?±?0.11 21.9 190?±?5 1020?±?2 HR75-2 HR75 reheated to 1080?°C for 1?h 76.1?±?45.3 24.0?±?10.6 2.7?±?1.0 0.44?±?0.18 56.6 125?±?1 913?±?3