GOALI: Welding Bulk Amorphous Alloys and Producing Fully Amorphous Joints Using Reactive Multilayers

金属玻璃是一类革命性的合金，它具有金属的卓越机械性能，但也可以很容易地形成复杂的形状，很像聚合物。然而，一个限制是难以将单个金属玻璃部件连接到更大的组件中。传统的焊接技术很难应用于金属玻璃，因为加热容易使合金晶化，降低其力学性能。连接金属玻璃的一种有前途的方法是使用反应性多层箔，这是一种新型的纳米工程材料，由数百层相互作用的纳米级元素组成，具有强烈的相互反应倾向。在这种具有小火花的箔中可以产生极快的化学反应，在千分之几秒内产生1500摄氏度或更高的温度。这使得使用反应性多层膜作为连接金属玻璃的局部热源成为可能。由于加热在界面处高度局部化且容易消散，反应性多层膜非常适合连接热敏性材料，包括金属玻璃。通过结合实验和计算工具，箔的设计将得到优化，以生产高强度、高韧性的接头。第二个目标是开发一种全新的多层膜，这种多层膜本身由于化学反应而形成非晶态金属相(类似于金属玻璃)。由于非晶态合金在低温下会软化，具有良好的润湿特性，并且坚固坚韧，因此这些箔应该是粘接各种工程材料的优秀材料。在这个目标计划中，来自约翰霍普金斯大学和Howmet研究公司的研究人员将合作开发为连接金属玻璃量身定做的反应性多层膜。作为这种互动的一部分，研究生每年将在Howmet现场呆上几个月。除了产业界和学术界的互动，私人投资机构将继续增加他们在本科生参与研究的强劲记录，包括女性和少数族裔学生。

Metallic glasses are a revolutionary class of alloys that have the outstanding mechanical properties of metals, but which may also easily formed into complex shapes, much like polymers. One limitation, however, is the difficulty in joining individual metallic glass components into larger assemblies. Traditional welding techniques cannot be easily applied to metallic glasses, because the heat applied tends to crystallize the alloys, degrading their mechanical properties.A promising approach to joining metallic glasses is to use reactive multilayer foils, which are a new class of nano-engineered materials consisting of hundreds of alternating nanoscale layers of elements which have a strong tendency to react with each other. An extremely rapid chemical reaction can be generated in such a foil with a small spark, generating temperatures of 1500 C or more in a few thousandths of a second. This makes it possible to use a reactive multilayer as a local heat source for joining metallic glasses. Because the heating is highly localized at the interface and readily dissipated, reactive multilayers are ideally suited to joining heat-sensitive materials, including metallic glasses. By combining experimental and computational tools, the design of the foils will be optimized to produce high strength, high toughness joints. A second goal is to develop an entirely new class of multilayers that themselves form amorphous metallic phases (similar to metallic glasses) as a result of the chemical reaction. Because amorphous alloys soften at low temperatures, have excellent wetting characteristics, and are strong and tough, these foils should be outstanding for bonding a wide variety of engineering materials. In this GOALI program, researchers from Johns Hopkins University and Howmet Research Corporation will work together to develop reactive multilayers tailored to joining of metallic glasses. As part of this interaction, graduate students will spend several months each year on site at Howmet. In addition to the industry-academia interaction, the PIs will continue to add to their strong record of undergraduate participation in research, including female and minority students.