期刊
出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2021.142584
关键词
Heterostructured materials; Hetero-deformation induced stress; Low-carbon martensitic steel; Nano-lamellae; Dual -phase structure
类别
资金
- Key Program of National Natural Science Foundation of China [51931003]
- National Natural Science Foundation of China [52071178, 51901103]
- Hong Kong Research Grants Council [GRF 11214121]
- Projects in Science and Technique Plans of Ningbo City [2019B10083]
- China Post-doctoral Science Foundation [2021M701715]
- Fundamental Research Funds for the Central Universities [30918011342]
The martensitic transformation greatly enhances the strength of low-carbon steels, but usually at the expense of ductility. By creating a dual-phase heterostructure through annealing and cold rolling, a high strength and ductility combination steel was achieved. The hetero-deformation induced stress in the sample contributed to the improved mechanical properties of the steel.
Martensitic transformation significantly increases the strength of low-carbon steels, while it is usually at expense of the formability and ductility. In order to further improve the mechanical properties of low carbon martensitic steel, the strategy of dual-phase heterostructure was proposed. The steel with nano-lamellar structure in size of 83 nm was produced by cyclic annealing & cold rolling (AnnCR) on the martensitic structure. Then, the ultrafine-grained heterostructured dual-phase (UFG-HSDP) steels with outstanding combination of strength and ductility were achieved by subsequent short-time intercritical annealing. A promising heterostructure of soft ferrite grains completely embedded in hard martensite grains was formed in the sample annealed at 820 degrees C. A high strength of similar to 1.1 GPa, close to the as-quenched full martensite steel, was retained in the HSDP steel. While, the uniform elongation was significantly improved to 6% by tailoring the dual-phase distribution. Hetero-deformation induced (HDI) stress, derived from the mechanical incompatibility of the dual-phase, is proposed to provide an extra strain hardening in the HSDP steels. Detailed microstructure analysis indicates that geometrically necessary dislocations piled-up near the zone interfaces produce a long-range back stress in the ferrite zones as well as a corresponding forward stress in the martensite zones, collectively resulting in the hetero-deformation induced (HDI) stress.
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