【摘要】 为优化后续热加工工艺，研究EA4T钢的热变形行为及微观组织演变规律。利用热模拟机对EA4T钢进行了单道次等温恒应变速率热压缩实验，变形温度为850～1 200℃,应变速率为0.01～10 s^-1,真应变为0.9。结果表明：EA4T钢在低应变速率下(850～1 200℃,0.01、0.1 s^-1)和高应变速率(950～1 200℃,1 s^-1)、(1 050～1 200℃,10 s^-1)条件下变形后发生了动态再结晶。动态再结晶可以通过改变微观组织从而决定钢的力学性能。将参数Z与微观组织演变结合，构建了EA4T钢的高温动态软化模型，可调控EA4T钢在热变形过程中发生动态回复、不完全动态再结晶、动态再结晶和晶粒长大的行为。采用电子背散射技术（EBSD）、透射电子显微测试等材料表征技术，分析了EA4T钢在不同变形条件下的动态再结晶晶粒、马氏体束的宽度和板条宽度的多尺度组织特征，建立了马氏体束宽与动态再结晶晶粒和变形参数Z的关系模型。研究结果可为EA4T钢热加工工艺提供理论指导。更多还原

【Abstract】 To optimize subsequent hot working processes, the thermal deformation behavior and microstructural evolution of EA4T steel were studied. The single-pass isothermal constant strain rate hot compression experiments were carried out with a thermal simulation testing machine. The true stress-true strain curves were obtained with the deformation temperature of 850-1 200 ℃ and strain rate of 0.01-10 s^-1, achieving a true strain of 0.9. The results show that the low strain rate(0.01, 0.1 s^-1) under all deformation temperatures show typical dynamic recrystallization characteristics. With the increase of strain rate, dynamic recrystallization occurred after hot compression deformation at high temperature and high strain rate(950-1 200 ℃, 1 s^-1) and(1 050-1 200 ℃, 10 s^-1). Recrystallization is important for steel processing because it modifies microstructure along the process route and thus determines the final properties of steel products. Then a dynamic softening model of EA4T steel at high temperature was established by combining Z parameter as hot deformation condition with microstructure evolution. The model can accurately regulate the behavior of dynamic recovery, incomplete dynamic recrystallization, complete dynamic recrystallization, and grain growth phenomena during hot deformation. EA4T steel has multi-level microstructure characteristics of dynamic recrystallization grains, martensite blocks and martensite laths under varying deformation conditions. The grain evolution of EA4T steel was clarified by means of electron backscattering diffraction（EBSD） and transmission electron microscopy（TEM）. The relationship model of dynamic recrystallization grains martensite blocks and Z parameters of EA4T steel was established. The results can provide theoretical guidance for hot working process of EA4T steel.更多还原