双相钢DP780在循环加载-卸载过程中的非弹性回复行为及其微观机理  

Inelastic recovery behavior and microscopic mechanism of high strength DP780 steel during cyclic loading-unloading

作　　者：徐虹[1] 刘亚楠[1] 于婷[1] 谷诤巍[1] 李湘吉[2] 张志强[1] XU Hong LIU Ya-nan YU Ting GU Zheng-wei LI Xiang-ji ZHANG Zhi-qiang(College of Materials Science and Engineering, Jilin University, Changchun 130022, China Roll Forging Research Institute, Jilin University, Changchun 130022, China)

机构地区：[1]吉林大学材料科学与工程学院,长春130022 [2]吉林大学辊锻工艺研究所,长春130022

出　　处：《吉林大学学报（工学版）》2017年第1期191-198,共8页Journal of Jilin University:Engineering and Technology Edition

基　　金：国家自然科学基金项目(51205162;51275203);吉林省科技发展计划项目(20130102021JC);吉林大学2015年大学生创新创业训练计划国家级培育项目(2015430451)

摘　　要：采用连续循环加载-卸载拉伸试验法研究了DP780的非弹性回复行为,确定了DP780在循环加载-卸载中应变回复的组成和比例。建立了卸载模量与塑性应变的数学模型。结合数值模拟和试验进行了模型验证。结果表明:DP780钢的平面各向异性不明显;由于卸载和重新加载循环非线性,卸载和重新加载轨迹构成了封闭环;卸载模量随着预应变的增大先快速下降,随后缓慢下降,在预应变达到6%后逐渐趋于稳定,卸载弹性模量降低17%;卸载总应变回复包括弹性部分和非弹性部分,并且后者所占比例高达11%。采用扫描电镜(SEM)和透射电镜(TEM)揭示了DP780非弹性回复的微观机理:塑性变形和奥氏体相变导致的位错密度增加,马氏体阻碍位错移动,造成大量的位错塞积,使可动位错发生弯曲,位错线长度增加,附加了弹性变形,导致了显著的非弹性回复行为。将得到的模型代入有限元模拟中,提高了模拟回弹的精度,使模具的回弹补偿更准确。The inelastic recovery behavior of DP780 steel was studied in continuous cyclic loadingunloading tensile tests.The composition of springback and the percentage of inelastic strain recovery of the steel were determined.Then,a mathematical model of unloading modulus and plastic strain was proposed.The model was verified by numerical simulation and experiment.It is shown that the plane anisotropy of DP780 steel is not obvious.The unloading and loading paths constitute a closed loop,which is formed due to the nonlinearity of the elastic modulus in the unloading and reloading cycles.With the increase of the pre-strain,the elastic modulus decreases rapidly,which then increases slowly and gradually tends to be stable after the pre-strain reaches 6%,the unloading elastic modulusdecreases by 17%.The total unloading strain recovery is composed of elastic strain recovery and inelastic strain recovery,and the inelastic strain recovery can reach as high as 11% of the total strain recovery.The microstructures of DP780 steel were detected by SEM and TEM,and the microscopic mechanism of the inelastic recovery was revealed.It is shown that the plastic deformation and austenitic phase transformation cause the increase of dislocation density;the martensite dislocation moving obstacles lead to a large amount of dislocation pile-up and the movable dislocation bending,increasing the length of the dislocation line and additional elastic deformation.This results in significant inelastic recovery behavior.Integrating the model to the finite element simulation improves the accuracy of simulated springback and the mold springback compensation is more accurate.

关 键 词：材料合成与加工工艺 DP780钢 弹性模量 封闭环 非弹性回复 位错塞积 

分 类 号：TG386[金属学及工艺—金属压力加工]