SA-765 Gr.Ⅱ钢的热变形行为及再结晶临界应变模型

Hot deformation behavior and recrystallization critical strain model of SA-765 Gr.Ⅱ steel

采用Gleeble-1500D型热模拟实验机进行SA-765 Gr.Ⅱ钢等温热压缩实验,压缩变形温度分别为1000、1050、1100、1150和1200℃,应变速率分别为0.005、0.01和1 s^(-1),最大压缩变形量为50%。基于热压缩变形过程的真应力-真应变数据,采用加工硬化率法和三次多项式拟合,求得不同变形条件下SA-765 Gr.Ⅱ钢的临界应力与临界应变,建立了关联Zener-Hollomon参数的动态再结晶临界应变模型。结果表明:变形温度和应变速率会极大地影响SA-765 Gr.Ⅱ钢的动态再结晶机制的启动,动态再结晶临界应变与变形温度成反比,与应变速率成正比。动态再结晶临界应变模型为:ε_(c)=0.201035Z^(0.000402),依据模型计算得到的临界应变预测值与实验值之间的相关系数达到了0.9765。

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 ε_(c)=0.201035Z^(0.000402),and the correlation coefficient between the predicted critical strain value calculated based on the model and the experimental value reaches 0.9765.