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Vol.36, No.2, 151 ~ 159, 1998
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| Title |
| Deformation Induced Martensitic Transformation in a Fe-C-Si-Mn Steel |
| 김성규 , 신홍철 , 정진환 , 장영원 Sung Kyu Kim , Hong Chul Shin , Jin Hwan Chung , Young Won Chang |
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| Abstract |
| Deformation induced martensitic transformation in a steel containing retained austenite(γ_R) has been studied to elucidate the relationship between the stability of retained austenite and the flow behavior depending on the various bainite transformation conditions. The operation of plasticity induced transformation is viewed here as an effective relaxation mechanism of internal strain energy accumulated during plastic deformation. A new kinetics equation for deformation induced transformation has been formulated, based on this relaxation concept of internal strain energy as, f/f_s=1-exp(-βε^n), with the parameter β characterizing the stability of retained austenite, n a deformation mode parameter and f_s denoting the saturation value of transformed martensite. The deformation mode parameter, n is found to be n=1.0 for this steel regardless of heat treatment conditions. The maximum elongation was obtained in a specimen annealed at 400℃ for 5min, corresponding to the minimum value of β. It is therefore concluded that the minimum value of β provides the steady transformation rate during plastic deformation resulting in the best combination of strength and ductility in high strength sheet steel. |
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