复合成形轧制铜极薄带变形局部化的晶体塑性有限元模拟

Prediction of Deformation Localization of Copper Foil Compound Forming Rolling Using Crystal Plasticity Finite Element Simulations

随极薄带厚度的进一步减薄,轧制极薄带变形由于轧件厚度/晶粒尺寸比值小的尺寸效应和变形程度导致各向异性与局部化已完全不同于轧制厚件时的变形特性。采用具有拉拔-压缩-剪切复合成形功能的微型异步轧机开展系列厚度铜极薄带的箔轧实验,结果表明复合成形轧制工艺和极薄带尺寸显著影响轧制力能参数与箔材质量。宏观有限元理论已不再适用出现这些新现象的极薄带轧制变形的建模。将嵌入初始晶粒形貌和取向等微观组织结构信息的介观晶体塑性有限元模型(CPFE)用于复合成形条件下铜极薄带轧制变形局部化的模拟与分析,指导箔轧工艺优化和提高箔材质量。晶粒层次的晶体塑性有限元模型,准确预测了单层晶铜极薄带轧制变形局部化的现象和趋势,模拟与实验的轧制力吻合较好,尤其是各向异性。随上下工作辊异速比的增大,箔材厚度方向剪切变形增强,变形带、滑移带形成且局部化趋势显著。晶粒变形局部化的差异,对轧制制备极薄带材的控形控性造成困难。

With the further thinning of the foil thickness,the anisotropy and localization of the foil rolling are completely different from the deformation characteristics of the rolled thick strip due to the size effect and deformation degree of the smaller thickness/grain size.The applicants have conducted the copper ultra-thin strip fabricating research recently with the use of a mini asynchronous rolling mill which has the function of carrying out the compound forming with tension,compression and shearing.The experiment results show that the compound forming process and the ratio of foil thickness and grain size significantly influence the mechanical properties and foils quality.Macro mechanicals finite element modelling cannot be used to simulate such new phenomena encountered in foil rolling process.In this work,plastic deforming localization of copper foil compound forming rolling was characterized by meso-scale crystal plasticity finite element(CPFE)simulations.Initial grain orientation and grain morphology determined from experiments were incorporated into a single-layer crystal microstructure generated by grain growth model.This work can be optimization of foil rolling process and improve the foil quality.CPFE simulations using such a grain-scale modelling accurately capture local deformation behaviors and evolution of foil rolling.The predicted roll force-time agrees well with experimental results,especially in regard to anisotropic behavior.With increase in the rolling speed ratio between the upper and lower rolls driving strong shear deformation along foil thickness direction,deformation and slip bands are formed and the localization trend is enhanced.Remarkable variations of plastic deformation localization occur in grains,making it difficult to control the shape and properties of copper foils in compound forming rolling process.