Abstract

Double-hit hot compression tests were carried on medium-carbon low-alloy steels using Gleeble 3800^® thermomechanical simulator. The experiments were performed at strain rates of 0.25 and 0.5 s⁻¹ and temperatures of 1150 and 1200 °C with interpass times of 5, 15, and 25 s. The onset of critical stresses for dynamic transformation (DT) for both first and second hit were detected using the double-differentiation method. It was found that the critical stress for DT increased with a decrease in temperature and an increase in strain rate. The presence of dynamically transformed ferrite was observed and quantified using electron-backscatter diffraction, kernal average misorientation, and grain boundary maps. Then, a thermodynamic analysis was carried out using JmatPro software. A method of determining the change in Gibbs energy during DT phenomenon is proposed for double hit deformation.

Graphic Abstract

中文翻译：

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二次热变形对动态变形铁素体演化的影响

摘要

双击热压缩试验是使用GLEEBLE 3800中碳低合金钢^®热模拟。实验在0.25和0.5 s ^-1的应变速率下进行温度为1150和1200°C，通过时间为5、15和25 s。使用双微分方法检测了第一次和第二次命中动态转变（DT）的临界应力的开始。发现DT的临界应力随着温度的降低和应变速率的增加而增加。观察到动态转变的铁素体的存在，并使用电子反向散射衍射，核平均取向差和晶界图进行了定量。然后，使用JmatPro软件进行热力学分析。针对双撞击变形，提出了一种确定DT现象期间吉布斯能量变化的方法。

图形摘要