Quantitative Analysis of Work Hardening and Dynamic Softening Behavior of low carbon alloy Steel Based on the Flow Stress |
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| Affiliation: | 1. School of Material Science and Engineering, Chong Qing University, Chongqing 400044, China;2. Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan;1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;2. Key Laboratory of Nonferrous Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China;1. School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522, Australia;2. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;3. School of Materials and Metallurgy, University of Science and Technology Liaoning, Anshan 114051, China;4. School of Electrical, Mechanical and Mechatronic Systems, University of Technology, Sydney, NSW 2007, Australia;5. Baosteel Research Institute, Baoshan Iron & Steel Co Ltd., Shanghai 200941, China;6. State Key Laboratory of Rolling and Automation, Northeastern Univertity, Shengyang 110004, China;1. Department of Materials Science Engineering, University of Bonab, P.O.Box: 5551761167, Bonab, Iran;2. Department of Materials Science Engineering, Sahand University of Technology, P.O.Box: 51335-1996, Tabriz, Iran;1. School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China;2. State Key Lab of Rolling Technologies and Automation, Northeastern University, Shenyang 110819, Liaoning, China |
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| Abstract: | In this study, the constitutive equation and DRX(Dynamic recrystallization) model of Nuclear Pressure Vessel Material 20MnNiMo steel were established to study the work hardening and dynamic softening behavior based on the flow behavior, which was investigated by hot compression experiment at temperature of 950 °C, 1050 °C, 1150 °C and 1250 °C with strain rate of 0.01 s?1, 0.1 s?1 and 10 s?1 on a thermo-mechanical simulator THE RMECMASTOR-Z. The critical conditions for the occurence of dynamic recrystallization were determined based on the strain hardening rate curves of 20MnNiMo steel. Then the model of volume fraction of DRX was established to analyze the DRX behavior based on flow curves. At last, the strain rate sensitivity and activation volume V* of 20MnNiMo steel were calculated to discuss the mechanisms of work hardening and dynamic softening during the hot forming process. The results show that the volume fraction of DRX is lower with the higher value of Z (Zener–Hollomon parameter), which indicated that the DRX fraction curves can accurately predicte the DRX behavior of 20MnNiMo steel. The storage and annihilation of dislocation at off-equilibrium saturation situation is the main reason that the strain has significant effects on SRS(Strain rate sensitivity) at the low strain rate of 0.01 s?1 and 0.1 s?1. While, the effects of temperature on the SRS are caused by the uniformity of microstructure distribution. And the cross-slip caused by dislocation piled up which beyond the grain boundaries or obstacles is related to the low activation volume under the high Z deformation conditions. Otherwise, the coarsening of DRX grains is the main reason for the high activation volume at low Z under the same strain conditions. |
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