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

金属玻璃是一种革命性的合金，它具有金属的杰出机械性能，但也很容易形成复杂的形状，就像聚合物一样。然而，有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。传统的焊接技术不容易应用于金属玻璃，因为所施加的热量容易使合金结晶，降低其机械性能。一种很有前途的连接金属玻璃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，由数百个相互反应的纳米级元素层组成。在这种箔中，一个小火花就能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作为连接金属玻璃的局部热源成为可能。由于加热高度局限于界面且易于消散，反应性多层膜非常适合连接热敏性材料，包括金属玻璃。通过实验和计算相结合的方法，优化设计出高强度、高韧性的接头。第二个目标是开发一种全新的多层材料，这种材料本身可以通过化学反应形成无定形金属相（类似于金属玻璃）。由于非晶合金在低温下软化，具有优异的润湿特性，并且坚固而坚韧，因此这些箔应该是粘合各种工程材料的杰出材料。在这个GOALI项目中，约翰霍普金斯大学和豪梅特研究公司的研究人员将共同开发适合金属玻璃连接的反应性多层材料。作为这种互动的一部分，研究生每年将花几个月的时间在Howmet现场。除了产学研的互动之外，私立学院还将继续增加其本科生参与研究的良好记录，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.