Transformation plasticity in high strength, ductile ultrafine-grained FeMn alloy processed by heavy ausforming
(2022) International Journal of Plasticity — Vol. 148, p. 103151 (2022)
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- Abstract
- The mechanisms contributing to the excellent mechanical properties of the ultrafine-grained (UFG) Fe-23 wt.%Mn alloy processed by heavy ausforming are unraveled based on detailed characterization analysis and modelling. The UFG microstructure is fully austenitic after the heavy ausforming step involving a 90% rolling reduction; while the material quenched from the coarse-grained (CG) austenite consists of epsilon (ε)-martensite and austenite. The UFG Fe23Mn alloy shows a high strain-hardening capacity which leads to a much higher true uniform elongation (0.33) and true tensile strength (1330 MPa) than the CG counterpart (0.17 and 950 MPa, respectively). The high ductility of the heavily-ausformed microstructure with no subsequent annealing step contradicts the general trend of UFG alloys produced by severe plastic deformation. In addition, a ductile fracture mode with improved resistance to damage initiation in the UFG microstructure contrasts with the brittleness of the CG counterpart. Therefore, the UFG Fe23Mn alloy exhibits a high combination of strength, resistance to plastic localization and resistance to cracking. This superior mechanical performance is attributed to the gradual deformation-induced ε-martensitic transformation and to the large plastic co-deformation of the UFG ε-martensite, in which twinning is suppressed at the expense of the activation of non-basal <c+a> slip. A mean-field micromechanical model is used to analyze the contribution of the phase transformation to plasticity, and to further rationalize the mechanical response of the UFG ε-martensite. This finding provides new insight into the effects of microstructural scale on the mechanical behavior of this class of transformation-induced plasticity (TRIP)-assisted alloys.
- Affiliations
Nanjing University of Science and Technology Herbert Gleiter Institute of Nanoscience Nanjing University of Science and Technology Nano- and Heterogeneous Structural Materials Research Center General Motors Global Research and Development China Science Lab
Citations
Lai, Q., Yang, H., Wei, Y., Zhou, H., Xiao, L., Ying, H., Lan, S., You, Z., Kou, Z., Feng, T., Lu, Q., Jacques, P., & Pardoen, T. (2022). Transformation plasticity in high strength, ductile ultrafine-grained FeMn alloy processed by heavy ausforming. International Journal of Plasticity, 148, 103151. https://doi.org/10.1016/j.ijplas.2021.103151 (Original work published 2022)