极薄带材成形中超延展现象的实验与机理研究

As the quick development in high technology field such as Micro manufacturing, the needs to metal foil is increasing，and the requirement to its quality is becoming strict. The applicants start foil forming research recently on our own mini Asynchronous rolling mill which has the function to carry out the compound forming with compress, shearing and drawing. The important progress have been made in 1) broken through the limit of minimum rolling thickness by traditional theory, 2) discover the extreme extensibility up to the elongation over 43,000% in rolling pure copper foil. Under this background, we propose to carry out the research on: 1) experiments to find working conditions and the internal reason appearing the extreme extensibility phenomenon, taking copper as the key material including steel, aluminum, titanium and so on; 2) analyzing the relationship between the micro structures and the size effect in rolling of microsize foil when the extreme extensibility phenomenon appeared; 3）setup a new theory to describe the minimum rolling thickness, taking the compound forming condition and the size effect into account, and then to validate it by experiment; 4) using the research results of extreme extensibility to optimize the foil production technology, to reduce the cost of foil forming by means of reducing and/or avoiding annealing. It is significance to setup the new theoretical frame, understand the rule of extreme extensibility for foil forming, and providing the guidance to the foil production by the high quality and low cost way, based upon this application research.

微制造等高技术领域的快速发展,对极薄带材成形提出了更高的要求。申请者利用自主开发、具有压缩、剪切、拉拔复合成形功能的新型异步轧机开展极薄带制备研究，取得了突破传统理论最小可轧厚度极限、发现工业纯铜在复合成形条件下呈现延伸率高达43,000%以上的超延展现象等重要进展，分析认为与微尺度效应有关。在此背景下提出针对以下关键科学问题开展研究：1）以铜为重点兼顾钢、铝、钛等金属材料，研究成形中出现超延展现象的外部加工条件及材料内部原因；2）分析微米级极薄带成形中微尺度效应与材料组织结构变化的关系，探讨普通金属材料出现超延伸现象的微观机理；3）建立复合成形条件下考虑微尺度效应的最小可轧厚度新理论，并进行实验验证；4）利用上述超延伸现象优化极薄带轧制工艺，通过减免退火以低成本方式获得微米级极薄带样件。通过本研究掌握超延伸现象的规律；建立极薄带轧制新理论框架；为低成本高质量极薄带生产提供理论指导。

金属极薄带作为微制造领域所需的材料，一直备受关注。本项目针对组合成形轧制极薄带时出现的超延展现象，对极薄带轧制开展了理论、实验及轧制工艺等多方面的研究。基于轧制实验和数据分析，以搓轧区比例为特征参数建立了异步轧制最小可轧厚度新公式，轧制实验数据与理论计算值吻合较好。对铜、铝和普碳钢进行的室温轧制实验研究发现，在特定加工条件下出现尺寸效应，材料厚度小于阈值时通常由加工硬化转变为加工软化，是普通金属材料出现超延展现象的内在原因，而组合成形条件下的负辊缝轧制有利于实现超延展。研究了出现尺寸效应时材料的力学性能、微观组织以及织构取向在轧制过程中的变化；负辊缝轧制在变形区内形成的强烈的三向压应力状态、因轧件减薄导致的高静水压力和表面层效应等均与超延展现象有关。基于组合成形理念开发了具有卓越减薄能力的组合成形轧机，并已在工业生产环境使用，实现了科技成果向生产力的转化。将超延展现象的研究发现用于指导现场轧制工艺优化，在工业生产环境下未经中间退火轧制出了厚度仅为0.016mm的不锈钢极薄带卷，为低成本极薄带生产积累了参考数据。