|About this Abstract
||2023 TMS Annual Meeting & Exhibition
||High Performance Steels
||Contradicting Role of Martensitic Transformation on Ductility and Toughness in a Medium Mn Steel
||C. Hu, C.P. Huang, Y.X. Liu, K. Y. Zhu , A. Perlade, MingXin Huang
|On-Site Speaker (Planned)
In this study, the tensile and fracture behaviors of a medium Mn steel fabricated by intercritical annealing (IA) and room-temperature quenching and partitioning (RT-Q&P) were investigated. IA steel consists of recrystallized ferrite and austenite, while RT-Q&P steel has martensite matrix and retained austenite. The austenite in IA steel has higher fraction and is less stable. High-resolution micro-digital image correlation reveals that strain localizes at boundaries in RT-Q&P steel and is concentrated in the austenite of IA steel, resulting in extensive martensitic transformation (MT) and promoting work hardening. However, this excessive transformation leads to decohesion at phase boundaries and premature fracture. The crack-initiation toughness of IA steel is 18% less due to frequent martensite cracking and intergranular decohesion. The hierarchical microstructure in RT-Q&P steel suppresses brittle fracture and enables significant crack tip blunting. The present work demonstrates that the potential trade-off of massive MT is the deterioration of fracture toughness.