Microstructure evolution and flow stress modeling of SA508Gr.4N steel during hot deformation process

• Published in: Cai liao gong cheng = Journal of materials engineering Vol. 49; no. 3; pp. 67 - 77
• Main Authors: Qiao, Shi-bin, He, Xi-kou, Liu, Jing-jie, Zhao, De-li, Liu, Zheng-dong
• Format: Journal Article
• Language: Chinese
• Published: Beijing Beijing Institute of Aeronautical Materials 01.03.2021; Journal of Materials Engineering
• Subjects: Chromium; Correlation coefficients; Deformation; Dynamic recrystallization; flow stress; Forging; Grain size; Grain structure; Heat treating; hot deformation; Low alloy steels; Model accuracy; Molybdenum; Nickel; sa508gr.4n steel; Strain rate; Temperature; Thermal simulation; True strain; True stress; Yield strength
• ISSN: 1001-4381; 1001-4381
• DOI: 10.11868/j.issn.1001-4381.2020.000566

The isothermal deformation behavior of Ni-Cr-Mo low alloy SA508Gr.4N steel at deformation temperature of 850-1200 ℃, strain rate of 0.001-1 s-1, and true strain of 0.9 was studied by using Gleeble-1500D thermal simulation testing machine.The physically based flow stress model including dynamic recovery and dynamic recrystallization and the dynamic recrystallization grain size model were established,and the suitable forging process to avoid the coarse grain structure heredities was put forward.The results show that as the deformation temperature increases and the strain rate decreases, the dynamic recrystallization volume fraction and grain size gradually increase; the true stress-true strain curve of SA508Gr.4N steel has an obvious discontinuous dynamic recrystallization phenomenon;by comparing the experimental value with the predicted value of the model, the correlation coefficient (R) and mean relative error (MRE) of the flow stress model are 0.998 and 4.76%, respectively, and the correlation coefficient (R