Hot deformation behavior and recrystallization critical strain model of SA-765 Gr.Ⅱ steel
The Gleeble-1500D thermal simulation testing machine was used to conduct isothermal compression experiments on SA-765 Gr.II steel.The compression deformation temperatures were 1000,1050,1100,1150 and 1200℃,respectively,with strain rates of 0.005,0.01,and 1 s-1,and a maximum compression deformation of 50%.Based on the true stress-true strain data of the hot compression deformation process,the critical stress and critical strain of the SA-765 Gr.II steel under different deformation conditions were obtained using the work hardening rate method and cubic polynomial fitting,and a dynamic recrystallization critical strain mode associated with Zener-Hollomon parameters was established.The results show that the deformation temperature and strain rate greatly affect the initiation of dynamic recrystallization mechanism in the SA-765 Gr.II steel.The critical strain of dynamic recrystallization is inversely proportional to deformation temperature and directly proportional to strain rate.The dynamic recrystallization critical strain model is εc=0.201035Z0.000402,and the correlation coefficient between the predicted critical strain value calculated based on the model and the experimental value reaches 0.9765.
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