高铝高强钢动态再结晶行为研究

Study on dynamic recrystallization behavior of high aluminum high strength steel

采用Gleeble-3500热模拟试验机对高铝高强钢在变形速率为0. 01~10 s^-1、变形温度为925~1225℃的热变形条件下进行压缩试验,以真应力-应变曲线为基础数据研究其高温再结晶行为。通过对晶粒尺寸的统计来探究热变形条件对热变形后晶粒尺寸的影响。通过处理加工硬化率-应力曲线,标定数据中能揭示动态再结晶演变过程的3个特征点,即临界应变、峰值应变及最大软化速率应变。引入表征晶体动力学的双曲正弦模型,通过线性回归求解得到动态再结晶激活能Q,建立流变应力本构方程,并引入Z参数作为预测发生再结晶程度的依据。结果表明:高铝高强钢热加工过程是加工硬化和再结晶软化共同作用的。在发生再结晶条件范围内,Z值越小,发生动态再结晶的程度越大。

Compression experiments were carried out on high aluminum high strength steel under thermal deformation conditions with deformation rate of 0. 01-10 s^-1 and deformation temperature of 925-1225 ℃ by Gleeble-3500 thermal simulater. The high temperature recrystallization behavior was studied based on the true stress-strain curves. The effect of thermal deformation conditions on grain size after thermal deformation was investigated by calculating the grain size. The three feature points in data which can reveal the evolution of dynamic recrystallization,namely critical strain,peak strain and maximum softening rate strain,were marked by processing hardening rate-stress curve,respectively. The hyperbolic sinusoidal model representing crystal dynamics was introduced,and the dynamic recrystallization activation energy Q was obtained by linear regression. The flow stress constitutive equation was established and the Z parameter was introduced as the basis for predicting the degree of recrystallization. The results show that the hot working process of high aluminum high strength steel is a combination of work hardening and recrystallization softening. The smaller the Z value is,the greater the degree of dynamic recrystallization occurs within the range of recrystallization conditions is.