Partitioning of C and Mn During Intercritical Annealing and Transformation of Retained Austenite During Deformation in Medium Mn Steel

• Published in: Steel research international 2023-07, Vol.94 (7), p.n/a
• Main Authors: Tian, Geng, Li, Zhen, Yao, Shun, Qie, Rongjian, Cui, Yifu, Zhao, Aimin
• Format: Article
• Language: English
• Subjects: Annealing; Chemical composition; Deformation; Elongation; Grain boundaries; intercritical annealing; interface orientation relationship; Manganese steels; Martensite; Mechanical properties; medium Mn steels; Partitioning; Retained austenite; retained austenites; Transformations
• ISSN: 1611-3683; 1869-344X
• DOI: 10.1002/srin.202200731

Herein, high‐strength medium Mn steel is obtained by intercritical annealing and quenching processes. Experimental steel with a chemical composition of Fe–0.2C–8.0Mn–1.6Si–1.3Al (wt%) is treated. The microstructures of the obtained samples comprise ferrite/martensite and retained austenite (RA) phases. The partitioning behavior of carbon and manganese during the intercritical annealing process is simulated using DICTRA. The sample annealed at 700 °C for 10 min has the best mechanical properties, with a product of strength and elongation as high as 47.25 GPa%. The deformation response of the RA is studied. The γ→α′ transformation mainly occurs in the early stage of deformation, whereas the γ→ε→α′ transformation mainly occurs in the later stage of deformation. The stress is mainly distributed at the deformed martensite and RA, and most of the stress is concentrated at the low‐angle grain boundary. During the deformation process, both the Kurdjumov–Sachs interface and the Nishiyama–Wasserman interface between the RA and deformed martensite decrease, but the Kurdjumov–Sachs interface decreases more obviously. There are specific interface orientation relationships between retained austenite (RA) and martensite in medium Mn steel. These interface orientation relationships also vary during deformation process. During the deformation process, both the Kurdjumov–Sachs interface and the Nishiyama–Wasserman interface between the RA and deformed martensite decrease, but the Kurdjumov–Sachs interface decreases more obviously.