Rapid reversion of martensite in low-alloy steel under electropulsing treatment: Exploring feasibility of reversible transformation

• Published in: Materials characterization Vol. 217; p. 114436
• Main Authors: Xu, Xiaofeng, Fu, Xingguo, Wu, Chao, Wu, Zhicheng, Wei, Lai, Yu, Yongqiang, Yang, Xiaohu, Tian, Tian
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.11.2024
• Subjects: Austenite reversion; Cementite; Electropulsing; Low-alloy steel; Reversibility; Low-alloy steel; Reversibility; Electropulsing; Cementite; Austenite reversion
• ISSN: 1044-5803
• DOI: 10.1016/j.matchar.2024.114436

Reversibility is an essential feature of martensitic transformation but is always believed impossible in FeC alloys since martensite (α') is unstable, which decomposes and forms cementite (θ) before reversion begins. Here we used electropulsing treatment (EPT) to inhibit θ precipitation and explored the feasibility of reversible transformation without α' decomposition in low-alloy steels (22MnB5 and 35CrMo steels). The reversion behaviors of the electropulsed specimens were analyzed by morphology, orientation, elemental distribution, and final microstructure. The result shows that in low carbon, low-alloy steel (22MnB5 steel), acicular γ abruptly grows through the whole pack without composition change. The prior γ grains are reproduced with the same grain size, shape, and orientation, indicating that inhibiting the θ precipitation does make steels with low carbon content achieve the reversibility of martensitic transformation. This phenomenon mainly results from reducing the effective driving force for θ precipitation by the current. However, in low-alloy steel with higher carbon content (35CrMo steel), 3D orientation distributions reveal that the prior γ grain is divided into equiaxed grains with various orientations and irregular grains with slightly changed orientations. This result suggests that when carbon content increases above a limit, high dislocation densities lead to recrystallization and destroy the original orientation relationship. •In this work, it is the first time to use experiments to inhibit cementite precipitation during reheating and explore the possibility of reversibility of martensite in low-alloy steel.•It is proved by morphology, element distribution, orientation, and austenitic kinetic that electropulsing treatment realize diffusionless reversion, which is the first time verifying the reversibility of martensitic transformation by experiment.•For steel with high carbon content, the appearance of recrystallization means that the reversibility of martensite may not be achieved by only inhibiting cementite precipitation.