奥氏体耐热钢20Cr-25Ni-1.5MoNbTiN的热压缩变形行为

Hot compression deformation behavior of 20Cr-25Ni-1.5MoNbTiN austenitic heat resistant steel

利用Gleeble3800热模拟试验机对20Cr-25Ni-1.5MoNbTiN奥氏体耐热钢在温度为930-1230℃、应变速率为0.005-5 s^-1条件下进行热压缩试验,获得不同热压缩条件下的流变应力曲线,用光学显微镜观察热压缩试样的显微组织。结果表明：变形温度相同时,随应变速率增大动态再结晶程度逐渐减小,甚至完全处于加工硬化状态,其热激活能为328 k J/mol;当应变速率为5 s^-1、变形温度为1130-1230℃、应变量较小时和应变速率为0.005 s^-1、变形温度930-1230℃、应变量较大时,出现失稳现象;动态再结晶的临界应力与Z参数之间成线性关系,峰值应力与应变速率和变形温度也有线性关系。

The hot compression deformation behavior of 20Cr-25Ni-1.5MoNbTiN austenitic heat-resistant steel at 930-1230 ℃ and strain rate of 0. 005-5 s^-1 was investigated by using a Gleeble 3800 thermal mechanical simulator. The flow stress curves of the steel under different thermal compression conditions were obtained and the microstructure was observed by optical microscope. The results show that under the same deformation temperature,with the increasing of strain rate,the dynamic recrystallization degree of the steel decreases,and is even in the state of working hardening,and its thermal activation energy is 328 k J/mol. The instability phenomenon appears in the flow stress curves when the strain rate is 5 s^-1,deformation temperature is 1130-1230 ℃ and the strain is low,or when the strain rate is0. 005 s^-1,deformation temperature is 930-1130 ℃ and the strain is high. There is a linear relationship between the critical stress of dynamic recrystallization and the Z parameter,and the peak stress is linearly related to the strain rate and the deformation temperature.