复合轧制制备纳米晶铜极薄带尺寸效应研究

As the rapid development in high technology field such as microminiaturization of electronic products and micro manufacturing, leading to a higher demand for metal foils (copper foil, etc.), and the requirement to its quality is becoming strict. The applicants conduct this nanocrystalline copper ultra-thin strip fabricating research recently with the use of our own mini asynchronous rolling mill which has the function of carrying out the compound forming with tension, compression and shearing. Aiming at the essential characteristics of new process, such as compound forming and non-annealing, which are significantly different from the traditional foil rolling technology. The common problems of microstructure, plastic deformation mechanism, size effect and control of micro-forming are studied in the fabrication of nanocrystalline copper ultra-thin strip. Reveal the plastic deformation mechanism of nanocrystalline copper ultra-thin strip and its relationship with microstructure during compound rolling. Experiments and simulations are carried out to clarify the external forming conditions and the internal microstructure characteristics of the material which appears the size effect in compound rolling. Analyzing the effect of size effect on micro-forming property of nanocrystalline copper ultra-thin strip, and then exploring the accurate description of size effect in material theory. Based on this, the key theoretical points for controlling the microstructure and properties of nanocrystalline copper ultra-thin strip under compound forming condition are established. Using the research results of size effect to optimize the foil rolling technology, to reduce the cost and continuous production process of nanocrystalline copper ultra-thin strip by means of reducing and/or avoiding annealing. It is significance to understand the rule of size effect for foil rolling, and providing the guidance to the foil production and its micro-forming control by the high quality and low cost way, based upon this application research.

随着电子产品微型化和微制造等高技术领域的快速发展，对铜等极薄带材成形提出了更高的要求。本项目将具有拉拔-压缩-剪切复合成形功能的微型异步轧机引入纳米晶铜极薄带的制备过程，针对新工艺的复合成形、免退火等显著区别于传统箔材工艺的本质特点，围绕在纳米晶铜极薄带制备中共性的微观组织、塑性变形机理、尺寸效应、微成形控制问题开展研究。揭示复合轧制制备纳米晶铜极薄带的塑性变形机理及其与微观组织结构之间的关系，阐明纳米晶铜极薄带材成形中出现尺寸效应的外部加工条件及材料内部原因，分析尺寸效应对纳米晶铜极薄带微成形性能的影响规律，探索尺寸效应在材料理论上的准确描述，据此建立复合成形条件下纳米晶铜极薄带组织性能控制的关键理论要点，利用尺寸效应优化极薄带轧制工艺，通过减免退火以低成本连续化方式获得纳米晶铜极薄带样品。通过本研究掌握尺寸效应的规律，为低成本高质量极薄带材生产及其微成形控制提供理论指导。

随着电子产品微型化和微制造技术兴起，铜箔在电子、微机电、医疗及新能源领域中的应用日渐广泛，对超薄铜箔制备与成形提出了更高的要求与需求。针对传统压延铜箔采用多辊轧机生产控制复杂及电解铜箔组织缺陷，根据项目计划书，团队成员利用自主研制、具有拉拔-压缩-剪切复合成形功能的微型异步轧机开展了纳米晶铜极薄带制备研究，在复合成形和无中间退火条件下成功制备出了厚度100μm以下板形良好的系列铜箔样品，超过传统理论最小可轧厚度极限，分析了超薄轧制的铜箔内部微观机理和尺寸效应机制。在项目研究期间主要对以下关键科学问题开展了研究：1）以纯铜为重点，研究了超薄铜箔轧制成形中出现尺寸效应的外部加工条件及铜箔内部组织特征，探明了出现尺寸效应时复合轧制工艺和铜箔组织状态，铜箔晶粒组织在轧薄过程中的演化形态与尺寸效应有关；2）晶体塑性理论将微观结构特征引入到材料成形过程数值模拟的本构框架内，由晶粒的细观响应得出材料的微观塑性变形行为，并将金属的塑性变形归结为位错运动和晶格旋转，能够深刻揭示材料变形的本质。与此同时，有限元法也已成为求解材料成形的有效工具。基于连续变分原理描述非均质各向异性晶体材料弹塑性变形的晶体塑性有限元法将两者有机地结合在一起，已经被广泛地用于预测材料的微观组织结构、工艺设计和各种材料变形模拟，这是传统塑性变形理论无法比拟的。以晶体塑性有限元模拟为手段，研究了超薄铜箔复合轧制成形的物理本质及晶内-晶间滑移特性；3）建立了纳米晶铜极薄带复合轧制成形中尺寸效应与材料组织结构及厚度阈值之间的联系，对系列铜箔进行轧制实验表明，当铜箔厚度在76μm时出现尺寸效应现象，厚度76μm以下轧制铜箔的显微硬度出现降低，表现出加工软化现象，研究了轧制超薄铜箔出现尺寸效应的现象及其微观机制。通过本项目研究掌握了轧制超薄铜箔出现尺寸效应的规律及机理，利于优化铜箔轧制工艺，可为低成本制备高质量超薄高精度铜箔提供理论指导。