Ultrafine ferrite formation through cold-rolling and annealing of low-carbon dual-phase steel |
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| Authors: | Y. Okitsu N. Takata N. Tsuji |
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| Affiliation: | 1. Automobile R&2. D Center, Honda R&3. D Co., Ltd, 4930 Shimotakanezawa, Haga-machi, Haga-gun, Tochigi 321-3393, Japan;4. Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1-S8-8, Ookayama, Meguro-ku, Tokyo 152-8552, Japan;5. Department of Materials Science and Engineering, Graduate School of Engineering, Kyoto University Elements Strategy Initiative for Structural Materials (ESISM), Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501, Japan |
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| Abstract: | Formation process of ultrafine grained ferrite through a simple thermomechanical route composed of cold-rolling and annealing of dual-phase starting microstructures was investigated. A 0·1%C steel having a ferrite–martensite dual-phase microstructure was cold-rolled by 91% and subsequently annealed below the eutectoid (A1) temperature. During the annealing, the cold-rolled microstructure gradually changed to be equiaxed ultrafine ferrite, without preferential growth of particular ferrite grains. Hardness of the cold-rolled specimen continuously decreased without a significant drop. The main components of texture in the cold-rolled specimen, α-fibre and γ-fibre, did not change greatly after the formation of ultrafine grains. It was suggested that finely subdivided region having large misorientations in the cold-rolled state grew with recovery to form the ultrafine ferrite. |
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| Keywords: | Ultrafine grain Carbon steels Severe plastic deformation Cold rolling Dual phase steels Martensite |
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