Deformation mechanisms for a new medium-Mn steel with 1.1 GPa yield strength and 50% uniform elongation. (1st January 2023)

• Record Type: Journal Article
• Authors: Wang, Wei; Liu, Yanke; Zhang, Zihan; Yang, Muxin; Zhou, Lingling; Wang, Jing; Jiang, Ping; Yuan, Fuping; Wu, Xiaolei
• Is Part Of: Journal of materials science & technology. Volume 132(2023)
• Page Start: 110
• Page End: 118
• Publication Date: 2023-01-01
• Subjects: Medium-Mn steel -- Strain hardening -- Ductility -- Martensite transformation -- Strain gradient -- Mobile dislocations; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2022.05.048
• Languages: English
• ISSNs: 1005-0302

Abstract

Highlights: A novel medium-Mn steel was designed to achieve unprecedented tensile properties. Martensite transformation results in a persistent and complete TRIP effect. Strain gradients induce strong heter-deformation-induced hardening. Interstitial C atoms play a vital role in dislocation multiplication. Abstract: A new medium-Mn steel was designed to achieve unprecedented tensile properties, with a yield strength beyond 1.1 GPa and a uniform elongation over 50%. The tensile behavior shows a heterogeneous deformation feature, which displays a yield drop followed by a large Lüders band strain and several Portevin-Le Châtelier bands. Multiple strain hardening mechanisms for excellent tensile properties were revealed. Firstly, non-uniform martensite transformation occurs only within a localized deformation band, and initiation and propagation of every localized deformation band need only a small amount of martensite transformation, which can provide a persistent and complete transformation-induced-plasticity effect during a large strain range. Secondly, geometrically necessary dislocations induced from macroscopic strain gradient at the front of localized deformation band and microscopic strain gradient among various phases provide strong heter-deformation-induced hardening. Lastly, martensite formed by displacive shear transformation can inherently generate a high density of mobile screw dislocations, and interstitial C atoms segregated at phase boundaries and enriched in austenite play a vital role in the dislocation multiplication due to the dynamic strain aging effect, and these two effects provide a high density of mobile dislocations for strong strain hardening.