铜/镍复层薄板介观尺度塑性变形行为及微成形机理研究

Focusing on the controllable manufacturing difficulties in the process of continuous miniaturization and material recombination of key micro-parts in the new micro/nano devices and systems, microforming technology is proposed to manufacture clad metal micro-parts in this project. The plastic deformation behaviors of Cu/Ni clad thin sheets in mesoscale are investigated systematically. A material constitutive model is constructed to reveal the mechanism of flow stress size effect in microforming of clad metal thin sheets considering the influence of the coupling effects of multi-parameters. A new method for testing and analysing the evolution behavior of microcrack based on the imaging technologies through scanning electron microscope and the synchrotron radiation X-ray integrated with in-situ micro-tensile test is proposed. The fracture micromechanism of clad metal thin sheets in mesoscale is revealed in multiple aspects from two-dimentional static analysis to three-dimensional dynamic analysis. The forming limit diagram (FLD) of clad metal thin sheets is plotted by means of micro-tensile and micro-bulging experiments based on digital image correlation (DIC) technique. A theoretical model for forming limit of clad metal thin sheets by considering the surface roughening behavior is built based on the M-K theory. Accordingly, an experimental platform for precise microforming of microchannels of clad metal bipolar plate is established. The interaction and influence of multi-parameters on the forming process of microchannels are investigated to determine the optimal process scheme and achieve controllable fabrication of micro-components with high quality. The implementation of this project provides a theoretical basis and technical support for microforming of clad metal thin sheets, and plays an important role in further promoting the microforming technology and its application as well as the plastic forming theory.

本项目针对新型微纳器件与系统中核心微型构件在不断微型化与材料复合化进程中带来的可控制造难题，提出采用塑性微成形技术制造复层金属微型构件。系统研究铜/镍复层薄板介观尺度塑性变形行为，构建考虑多参数耦合作用影响的材料本构模型，揭示流动应力尺度效应机理；提出一种基于扫描电子显微镜和同步辐射X射线原位微拉伸成像技术相结合的微裂纹演化行为测试分析新方法，从二维静态和三维动态多角度出发揭示复层薄板断裂微观机制；利用基于数字图像相关技术的微拉伸和微胀形实验绘制复层薄板成形极限图，基于M-K理论，构建考虑表面粗化行为影响的复层薄板成形极限理论模型。搭建复层金属双极板微流道结构微成形实验平台，分析多参数交互作用及影响，确定最佳工艺方案，实现复层金属双极板微流道结构高质量可控成形。项目的实施为复层薄板微结构件精确成形提供重要的理论依据和技术支撑，对促进微成形技术发展和应用以及推动塑性成形理论发展具有重要意义。

针对新型微纳器件与系统中核心微型构件在不断微型化与材料复合化进程中带来的可控制造难题，提出了采用塑性微成形技术制造复层金属微型构件的解决方案。系统研究了试样厚度、试样取向、基体晶粒尺寸等对Cu/Ni复层箔微拉伸流动应力的影响，发现了随着热处理温度的升高，基体Cu层和Ni层的晶粒尺寸增大而导致其流动应力降低，同时材料RD方向流动应力最高，45°方向流动应力最低，热处理温度升高后，其流动应力出现明显各向异性的现象。基于混合法则和表面层模型构建了Cu/Ni复层箔塑性变形材料本构，揭示了其流动应力尺度效应机理。发现了Cu/Ni复层箔延伸率随热处理温度的变化趋势不明显现象，这有别于介观尺度单层箔延伸率变化趋势。结合宏微观断口分析和中断实验，发现了Cu/Ni复层箔拉伸塑性变形过程中断裂是按照界面层处形成裂纹-裂纹扩展-镍层-断裂-铜层断裂，直至整个复层箔断裂的规律。发现了Cu/Ni复层箔V型软模微弯曲实验中材料越薄时材料受到应变梯度影响产生的硬化行为越大，材料的回弹角度越大的现象，考虑材料中部分晶粒因受到模具约束而与其他晶粒的约束情况产生差异，引入模具约束层晶粒概念，构建了V型软模微弯曲的回弹角度计算模型，预测了材料在介观尺度下进行微弯曲发生的回弹行为。利用基于数字图像相关技术的微拉伸和微胀形实验绘制了Cu/Ni复层箔成形极限图，建立了一种考虑尺度效应影响下表面粗化与孔洞演化耦合的多级分段复合损伤模型，揭示了Cu/Ni复层箔成形极限尺度效应机理。在此基础上开展了微流道和双极板成形工艺研究，实现了超薄板微小结构件高质量可控制造，项目的研究成果为复层薄板微结构件精确成形提供重要的理论依据和技术支撑，对促进微成形技术发展和应用以及推动塑性成形理论发展具有重要意义。