High-temperature deformation mechanisms and physical-based constitutive modeling of ultra-supercritical rotor steel
High-temperature deformation mechanisms and physical-based constitutive modeling of ultra-supercritical rotor steel
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超超临界转子钢的高温变形机制和物理本构模型
DOI：
10.1016/j.jmapro.2019.01.021
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发表时间：
2019-02-01
影响因子：
6.2
通讯作者：
Cui, Zhenshan
中科院分区：
文献类型：
--
作者：
Chen, Fei;Wang, He;Cui, Zhenshan
采用Gleeble-3500热模拟试验机，研究了FB 2转子钢在900 ℃ ~ 1200 ℃温度范围内，应变速率为0.001s（-1）~ 0.1s（-1）的热变形过程中动态再结晶组织和流变行为的演变规律。动态再结晶（DRX）是FB 2转子钢热变形软化机制的关键。随着变形温度的降低，LABs的含量显著增加。低角度晶界（LAB）通常具有较高的局部取向差角，这意味着较低的变形温度不能为LAB的迁移提供足够的驱动力，从而减缓了DRX过程以消耗位错。通过对三次多项式的二阶导数的设定，计算了动态再结晶的临界应力和临界应变。基于经典的应力-位错关系和动态再结晶动力学，建立了FB 2钢流变应力的两阶段本构模型。预测和实测流变应力之间的比较表明，所建立的基于物理的本构模型可以准确地描述所研究的钢的热变形。
This study presents an investigation that characterizes the evolution of the dynamically recrystallized structure and flow behavior of FB2 rotor steel during hot deformation in the temperature range from 900 degrees C to 1200 degrees C at strain rates from 0.001s(-1) to 0.1s(-1) using Gleeble-3500 thermo-simulation machine. Dynamic recrystallization (DRX) plays a key role in softening mechanism for hot deformed FB2 rotor steel. The fraction of LABs greatly increases with the decrease of deformation temperature. Low angle boundaries (LABs) always have higher local misorientation angle, which means the lower deformation temperature is capable of providing not enough driven force for the migration of LABs and thereby decelerates the DRX process to consume the dislocations. Furthermore, the critical stress and critical strain for initiation of DRX are calculated by setting the second derivative of the third order polynomial. Based on the classical stress-dislocation relation and the kinetics of dynamic recrystallization, a two-stage constitutive model is developed to predict the flow stress of FB2 steel. Comparisons between the predicted and measured flow stress indicate that the established physically-based constitutive model can accurately characterize the hot deformations for the studied steel.