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通过对挤压态42CrMo高强钢在不同温度和应变速率下的热压缩实验获得真应力-应变曲线,作为研究其高温动态再结晶行为的底层数据。基于d#/dε-#曲线,识别了真应力-应变曲线上能表征动态再结晶演变过程的特征点:临界应变εc,峰值应变εp及最大软化速率应变ε*。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。设计无量纲参数Z/A,对已修正的Avrami方程作线性回归分析,表征了不同变形条件对挤压态42CrMo钢动态再结晶体积分数演变的影响,并详细描述了动态结晶对应力软化的影响。结果表明:在高应变速率下,发生剧烈的软化后趋于稳定;在低应变速率条件下,出现硬化和软化的周期性循环。
The true stress-strain curve of 42CrMo high-strength steel under different temperatures and strain rates was obtained as the underlying data to study the dynamic recrystallization at high temperature. Based on the d # / dε- # curve, the critical points on the true stress-strain curve that characterize the dynamic recrystallization process are identified: critical strain εc, peak strain εp and maximum softening rate strain ε *. The hyperbolic sine model which characterizes the crystal dynamics was introduced. The dynamic recrystallization activation energy Q was obtained by linear regression and the constitutive equation of flow stress was established. The dimensionless parameter Z / A was designed. The linear regression analysis of the modified Avrami equation was used to characterize the influence of different deformation conditions on the dynamic recrystallization volume fraction of extruded 42CrMo steel. The effect of dynamic crystallization on stress softening . The results show that under high strain rate, severe softening tends to be stable; at low strain rate, periodic cycles of hardening and softening occur.