Microstructural evolution and strain hardening mechanism of a boron-containing metastable austenitic steel

Quantitative tensile tests were carried out to study the microstructural evolution and strain hardening mechanism of a boron-containing metastable austenitic steel with 13 wt-% Mn and 0.30 wt-% B. The results indicate that the great mechanical properties come from two-stage TRIP effect and the true stress-strain curve can be divided into three stages during the tensile process. In the initial stage, part of the initial austenite transformed to epsilon-martensite through the stacking faults. Then, alpha'-martensite was formed from austenite directly or through the epsilon-martensite formation, which led to a great rise on the strain hardening rate in this stage. In the last stage, decline of the strain hardening rate was observed due to the co-work between multiple phases and voids.