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

发布时间：2018-07-21 15:52

【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。
[Abstract]:The inelastic recovery behavior of DP780 was studied by continuous cyclic load-unloading tensile test. The composition and proportion of strain recovery of DP780 during cyclic loading and unloading were determined. A mathematical model of unloading modulus and plastic strain is established. The model is verified by numerical simulation and experiment. The results show that the plane anisotropy of the steel is not obvious, the unloading and reloading trajectories form a closed ring due to the nonlinearity of unloading and reloading cycles, the unloading modulus decreases rapidly with the increase of prestrain, and then decreases slowly. After the prestrain reaches 6%, the unload elastic modulus decreases by 17%, and the unloading total strain recovery includes the elastic part and the inelastic part, and the proportion of the latter is as high as 11%. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to reveal the microscopic mechanism of the inelastic recovery of DP780: the dislocation density increased due to plastic deformation and austenitic transformation, and the dislocation movement was hindered by martensite, resulting in a large amount of dislocation plug product. The flexible dislocation is bent, the length of the dislocation line is increased, and the elastic deformation is added, which leads to the obvious inelastic recovery behavior. The model is replaced by finite element simulation, which improves the precision of springback simulation and makes the springback compensation of die more accurate.
【作者单位】：吉林大学材料科学与工程学院;吉林大学辊锻工艺研究所;
【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)
【分类号】：TG142.1

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