Collaborative Research: Fundamentals of Material Behavior and Structure in Making Laminated Metal Composites with Assistance of Electrical Current in Bonding Operation

层压金属复合材料对于减轻运输车辆的重量和能源需求至关重要。然而，制造这些复合材料是困难的，昂贵的，和能源密集型的。为了制造层压金属复合材料，现有的方法包括通过变形过程施加较大的应力或压力来粘合多个金属板。在制造过程中，加热可以软化金属薄片，减少所需的力。一种可能更便宜、能耗更低、更可控的方法是使用外加电流代替纯热。在变形过程中驱动电流进入金属部件的行为可以将热量精确地定位到需要的地方，在制造过程中暂时软化金属。然而，局部电流如何以及为什么使金属软化还不完全清楚，特别是在同时施加力的情况下。该奖项支持基础研究，以提供对金属在同时电流和压力下如何软化和粘合的理解。这样的理解将使制造工艺的发展，生产更便宜和高质量的层压金属复合材料。反过来，这将有助于低成本生产燃油效率更高的交通工具，包括飞机和汽车。研究目的是通过微观和中观尺度的研究，揭示在电流和机械复合载荷作用下材料流动应力降低的基本现象。在这项研究中，电辅助的层压金属复合材料的静态键合将在西北大学进行。层压金属复合材料将在一系列压力和连续电流条件下制造。然后对这些样品的质量进行测试，以粘结强度为标准，并通过先进的表征技术进行分析。这些表征方法由卡内基梅隆大学实施，将使用电子显微镜将金属微观结构的各个方面与粘合强度联系起来，并确定电辅助变形机制。此外，实验将在显微镜内进行，以直观地观察在原位施加连续电流和压力下金属变形的动态。这些实验将对电流对微结构、变形行为和金属键合的影响提供新的认识。

Laminated metal composites are critical to reducing the weight and energy demands of transportation vehicles. However, the manufacture of these composites is difficult, costly, and energy intensive. To make laminated metal composites, existing methods involve applying large stresses or pressures to bond multiple metal sheets through a deformation process. Using heat can soften the metal sheets during manufacturing, reducing the amount of required force. A potentially cheaper, less energy intensive, and more controllable approach is to use applied electrical current instead of pure heat. The act of driving electrical current into a metal part during deformation can localize the heat to exactly where it is needed, temporarily softening the metal during a manufacturing process. However, how and why local current flow softens metals is not completely understood, particularly when force is simultaneously applied. This award supports fundamental research to provide the understanding of how metals soften and bond under simultaneous electrical current and pressure. Such understanding will enable the development of manufacturing processes that produce cheaper and high quality laminated metal composites. In turn, this will facilitate low-cost production of transportation vehicles with better fuel efficiency, including aircraft and automobiles.The research objective is to uncover the fundamental phenomena associated with the reduction of material flow stress under the combined electrical current and mechanical loads through the investigations at the micro- and meso- scales. In this study, electrically-assisted static bonding of laminated metal composites will be carried out at Northwestern University. Laminated metal composites will be fabricated under a range of pressure and continuous electrical current conditions. These samples will then be tested for quality, in terms of bond strength, and analyzed by advanced characterization techniques. These characterization approaches, carried out at Carnegie Mellon University, will use electron microscopy to correlate aspects of the metal microstructure to bond strength and to determine electrically-assisted deformation mechanisms. Furthermore, experiments will be conducted inside the microscope in order to visualize the dynamics of metal deformation under in situ applied continuous electrical current and pressure. Such experiments will provide new understanding on the effects of electrical current on microstructures, deformation behavior, and metal bonding.