20MnNiMo钢热塑性变形与动态再结晶软化的耦合行为  

Characterization of dynamic rescrystallization behavior of 20MnNiMo steel by thermal deformation

作　　者：权国政[1] 余春堂[1] 刘莹莹[1] 夏玉峰[1] 周杰[1] 

机构地区：[1]重庆大学材料科学与工程学院,重庆400030

出　　处：《材料热处理学报》2013年第8期177-183,共7页Transactions of Materials and Heat Treatment

基　　金：中央高校基本科研业务费(CDJPY12130001)

摘　　要：采用热物理模拟压缩实验获得退火态20MnNiMo钢在不同温度和应变速率下的真应力-应变曲线,作为计算动态再结晶模型的底层数据。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退火态20MnNiMo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,在应变后期发生剧烈软化;在中等应变速率下,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。Abstract：The true stress-strain curves of annealed 20MnNiMo steel at different temperatures and strain rates were obtained by isothermal compression tests on a Gleeble-1500 theromechanical simulator, which were taken as the basic data for characterizing the evolution of dynamic reerystallization （DRX）. From the dσ/dε versus σcurves, the characteristic points including the critical strain for DRX initiation （6o） , the strain for peak stress （ep） , and the strain for maximum softening rate （6~ ） were identified to express the evolution of DRX. By regression analysis for conventional hyperbolic sine equation, the activation energy Q was determined, and the flow stress constitutive equation was established. The regression analysis for a modified Avrami type equation by a dimensionless parameter Z/A was designed. The influence of deformation conditions on the evolution of DRX volume fraction was described in detail. The study of the effects of DRX on stress softening shows that at high strain rate, dramatic softening occurs in the late of strain, at medium strain rate, the stress is dramatic softening and then steady, and at low strain rate, there is a cycle of hardening and softening.

关 键 词：动态再结晶 临界应变 流动应力 硬化率 

分 类 号：TG142.7[一般工业技术—材料科学与工程] TB302.4[金属学及工艺—金属材料]