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<p>The laminated heterogeneous microstructure consisting of alternating ultrafine-grained (UFG) and coarse-grained (CG) layers with pronounced Mn concentration gradients was successfully developed in the Fe-0.2C-8.5Mn-1.5Al lightweight medium-Mn steel via a combined hot-rolling, cold-rolling, tempering, and annealing route. Microstructural evolution and underlying strengthening mechanisms of the heterogeneous microstructure during plastic deformation were systematically elucidated, with particular attention to the pronounced hetero-deformation induced (HDI) strengthening and the superior work-hardening response. The T6A660 specimen demonstrated optimal mechanical properties, with an ultimate tensile strength of 1392.4 MPa, an elongation of 51.0%, and a product of strength and ductility reaching 71.01 GPa·%. Its work-hardening process can be divided into four deformation stages, with the third stage playing a decisive role in balancing strength and ductility. This stage is characterized by the most pronounced reduction in austenite fraction, where the intensified TRIP effect provides substantial work hardening, thereby delaying necking and enhancing the overall mechanical performance. In contrast, the T6A700 specimen experienced brittle fracture, primarily due to the reduced stability of austenite.</p>

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Superior strength-ductility synergy in lightweight medium-Mn steel with laminated heterogeneous microstructure

  • 期刊论文

  • 发表日期：

    2025年12月29日

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  • Ying Sun,
  • Yufeng Gao,
  • Lianfang He,
  • Wendong Zhang,
  • Zhichao Li,
  • Huiping Li

摘要

The laminated heterogeneous microstructure consisting of alternating ultrafine-grained (UFG) and coarse-grained (CG) layers with pronounced Mn concentration gradients was successfully developed in the Fe-0.2C-8.5Mn-1.5Al lightweight medium-Mn steel via a combined hot-rolling, cold-rolling, tempering, and annealing route. Microstructural evolution and underlying strengthening mechanisms of the heterogeneous microstructure during plastic deformation were systematically elucidated, with particular attention to the pronounced hetero-deformation induced (HDI) strengthening and the superior work-hardening response. The T6A660 specimen demonstrated optimal mechanical properties, with an ultimate tensile strength of 1392.4 MPa, an elongation of 51.0%, and a product of strength and ductility reaching 71.01 GPa·%. Its work-hardening process can be divided into four deformation stages, with the third stage playing a decisive role in balancing strength and ductility. This stage is characterized by the most pronounced reduction in austenite fraction, where the intensified TRIP effect provides substantial work hardening, thereby delaying necking and enhancing the overall mechanical performance. In contrast, the T6A700 specimen experienced brittle fracture, primarily due to the reduced stability of austenite.