4不同相区热变形的流变应力与晶粒组织变化

DT4 steel exhibits significant difference in grain morphology at different deformation temperatures, especially with deformation in the two-phase region. In this study, the Gleeble 3800 thermal simulation machine was used to perform hot compression simulations on DT4 experimental steel at temperatures ranging from 850 to 1050 C, strain rates from 0.01 to 10s-1, and 60% deformation. The temperatures of the two-phase region of DT4 experimental steel were also calculated and analyzed, investigating the changes in flow stress and grain morphology with deformation in different phase regions. The results show that the calculated temperature points for the α-γ two-phase region by Thermo-Calc are 892-963 C, while the temperature points for the two-phase region during cooling at 0.1 C/s in the thermal expansion experiment are 868.2-937 C. With deformation in the α-γ two-phase region, the flow stress increases with the increase in temperature because the strength of the γ-Fe with fcc structure is higher than that of the α-Fe with bcc structure. Anomalies of single and double peaks in flow stress were observed at 900 C and 950 C in the hot compression experiment, and at 900 C, the grain morphology was complex and uneven. Attention should be paid to the complex situations arising from deformation in the two-phase region.