Manipulating Nanostructure During High-Speed Casting of Glassy Metals

在加工过程中，大多数金属如铁或铝将固化成有序的原子级晶体结构。 相反，如果在加工的最后阶段受到足够的阻碍，凝固的金属将缺乏原子尺度的有序性。 在这项研究中，一个平面流铸造工艺被用来产生一个无序的结构，称为玻璃金属。玻璃金属通常具有有利的性质，例如玻璃不锈钢的超高强度。 所研究的合金的有利电磁特性是它们能够在电动汽车电力系统、风能或光伏太阳能发电场和配电等应用中实现节能。这些特性可以通过引入精细特征或纳米结构来进一步增强。 这项研究提出了一种新的方法，将这些精细功能在平面流铸造。 能够使用本身具有低碳足迹的技术制造绿色产品对社会具有双重好处。 作为该项目的一部分，社区外展将培养学生对科学、技术、工程和数学的兴趣，特别是鼓励高中女生从事技术职业，目标是提高以每秒米的速度连续快速凝固薄金属玻璃合金的能力，同时实时控制纳米晶体的形成。 寻求控制结晶发生的程度和在固化产品中结晶发生的位置。在每秒米的生产速度下，这代表了前所未有的纳米结构控制。 这项工作的智力意义涉及到非平衡材料科学的快速转变，在原子尺度上的高热梯度的存在。 该方法将包括使用改进的平面流铸造机的实验，使用X射线衍射和透射电子显微镜的产品结构的表征，材料和基板内的温度场的模拟，以及金属对金属接触事件的数学建模。这一努力的结果也将对金属以外的材料的高速非平衡处理产生影响。

During processing, most metals such as iron or aluminum will solidify into an ordered atomic-scale crystalline structure. In contrast, if sufficiently hindered during the final stages of processing, solidified metals will lack atomic-scale order. In this study, a planar-flow casting process is used to produce a disordered structure known as glassy metal. Glassy metals often have favorable properties such as ultra-high strength for a glassy stainless steel. The favorable electromagnetic properties of the alloys under study are that they enable energy-savings in applications such as electric vehicle power systems, power harvesting from wind or photovoltaic sun farms and power distribution. Such properties can be further enhanced by incorporating fine features, or nanostructure. This study proposes a new approach to incorporating these fine features during planar flow casting. To be able to manufacture green-enabling products using a technique that itself has low carbon footprint represents a double benefit to society. As part of this project, community outreach will foster the interest of school children in science, technology, engineering and mathematics with a special focus aimed at encouraging high-school girls toward technical careers.The goal is to advance the ability to rapidly solidify thin metallic glass alloys continuously at speeds of meters per second, all while controlling in real-time the formation of nanocrystals. Control is sought of the extent to which crystallization occurs and where in the solidified product it occurs. At production speeds of meters per second, this represents unprecedented nanostructure control. The intellectual significance of this work relates to the non-equilibrium materials science of rapid transformations on the atomic scale in the presence of high thermal gradients. The approach will include experiments using a modified planar-flow casting machine, characterization of the product structure using X-ray diffraction and transmission electron microscopy, simulation of the temperature field within the material and substrate, and mathematical modeling of the metal-on-metal contacting event. The results of this effort will have impact on high speed non-equilibrium processing for materials other than metals as well.