T91钢的高温塑性变形及动态再结晶行为

采用Gleeble-1500热模拟试验机进行了T91钢的压缩试验,研究了变形温度为1100～1250℃、应变速率为0.01～1 s-1时该钢的变形行为,分析了流变应力与应变速率和变形温度之间的关系,计算了高温变形时应力指数和变形激活能,并采用Zener-Hollomon参数法构建该钢高温塑性变形的本构关系,绘制了动态再结晶图和热加工图.结果表明:在试验变形条件范围内,其真应力-真应变曲线呈双峰特征;钢中发生了明显的动态再结晶,且再结晶类型属于连续动态再结晶.T91钢的热变形激活能为484 kJ.mol-1,利用加工图确定了热变形的流变失稳区,结合力学性能,可以优先选择的变形温度为1200～1 250℃,应变速率不高于0.1 s-1.

Plastic deformation and dynamic recrystallization of T91 steel at high temperature

Hot compressive tests were carried out on a Gleeble-1500 thermal simulation test machine to investigate the hot deformation behavior of T91 steel at elevated temperatures of 1 100 to 1 250 ℃ and strain rates of 0.01 to 1 s-1.The relations of flow stress to strain rate and deformation temperature were analyzed for calculating the stress exponent and the deformation activation energy at the elevated temperatures.The constitutive equation was constructed by introducing the Zener-Hollomon parameter.The dynamic recrystallization map and the processing map of plastic deformation of T91 steel at the elevated temperatures were drawn.The true stress-strain curves of the steel show a bimodal characteristic.Distinct dynamic recrystallization takes place in the steel,and its mechanism is continuous dynamic recrystallization.The deformation activation energy of the steel is 484 kJ·mol-1.The instability zones and optimum processing parameters of hot deformation under the condition can be attained by using the two maps.The steel has excellent mechanical properties when rolled at deformation temperatures of 1 200 to 1 250 ℃ and strain rates which are not greater than 0.1 s-1.