Bicontinuous Nanocomposite Refractories

新金属的发现和开发对于需要高强度和延展性的技术应用至关重要。 在这个项目中，我们探索了一类新的大块纳米结构金属，这种金属是通过一种称为液态金属去合金化的先进加工方法制成的，在这种方法中，将钨和钛等难熔金属的合金浸入熔融铜中，在这种条件下，钛被溶解掉，难熔金属重新组织成纳米级网络，一种桁架网络，其韧带只有几百个原子。 在冷却时，复合材料是双连续的，即由不同材料的两个互穿网络组成，硬耐火相和延性铜相，结合每种金属的最佳属性以制造新型的坚固和延性材料。 在这个项目中，我们将探索制造这些新材料的加工方法，并以系统的方式测试它们的性能，以了解控制它们行为的基本材料物理学。 我们将通过学生的参与和课堂资源的发展来传播这种理解。Technical SummaryThis project will examine the structure/processing/property relationship of a new class of nanostructured metals，which possesses a bicontinuous？旋节分解？类似于微结构，但是其中一相是硬的难熔金属如钨，而另一相是延展性金属如铜。 这些材料是使用我们称为液态金属脱合金（LMD）的新方法制成的，其中钛/耐火合金在高温下浸入铜合金熔体中。 而钛溶解到铜中，耐火材料在熔体中是不混溶的，因此在浸没期间，它通过界面扩散重组成高度多孔的结构（要除去铜相），具有从大约50 nm到5000 nm的可调长度尺度。 该过程类似于电化学去合金化，例如用于产生纳米多孔金，不同之处在于LMD中的溶解是由热力学相行为驱动的，而不是电化学溶解。 我们在这里的重点是形成的动力学和通过这种方法制造的无孔复合材料的机械性能，这在各种应用中具有潜在的实用性，具有高韧性的超强材料。 更普遍和根本的是，在LMD过程中自发形成的双连续微结构是一个平台，在其上检查相变，动力学和机械的金属材料在纳米级。 除了科学技术驱动程序，该计划将涉及学生在动力学蒙特卡罗模拟代码的开发和传播的模拟和形态演变的动力学研究在纳米结构材料，这将补充一个新的本科教科书动力学和相变材料科学的发展。

Non-Technical SummaryThe discovery and development of new metals is critical for technical applications where high strength and ductility are necessary. In this program, we explore a new class of bulk nanostructured metals made by an advanced processing method called liquid metal dealloying, in which an alloy of a refractory metal such as tungsten and titanium is immersed into molten copper under conditions in which the titanium is dissolved away and the refractory metal re-organizes itself into a nanoscale network, a kind of truss network whose ligaments are only a few hundred atoms across. Upon cooling, the composite material is bicontinuous, i.e. comprised of two interpenetrating networks of distinct materials, a hard refractory phase and a ductile copper phase, combining the best attributes of each metal to make a novel strong and ductile material. In this program, we will explore processing methods to make these new materials and test their properties in systematic ways so as to understand the fundamental materials physics that govern their behavior. We will disseminate this understanding via student participation and the development of classroom resources.Technical SummaryThis project will examine the structure/processing/property relationship of a new class of nanostructured metals, which possess a bicontinuous ?spinodal decomposition?-like microstructure, but where one phase is a hard refractory metal such as tungsten and the other phase is a ductile metal such as copper. These materials are made using a new method we call liquid metal dealloying (LMD), in which titanium/refractory alloys are immersed in copper alloy melts at elevated temperatures. Whereas titanium dissolves out into the copper, the refractory is immiscible in the melt so during immersion it reorganizes via interface diffusion into a highly porous structure (were the copper phase to be removed), with a tunable lengthscale from approximately 50 nm to 5000 nm. The process is akin to electrochemical dealloying, such as is used to create nanoporous gold, except that dissolution in LMD is driven by thermodynamic phase behavior, and not electrochemical dissolution. Our focus here is on the kinetics of formation and the mechanical properties of non-porous composites fabricated by this method, which have potential utility in the diverse number of applications for ultra-strong materials with high toughness. More generally and fundamentally, the spontaneous formation of the bicontinuous microstructure during LMD is a platform on which to examine phase transformations, kinetics, and mechanical of metallic materials at the nanoscale. In addition to the scientific technology drivers, this program will involve students in the development and dissemination of kinetic Monte Carlo simulation code for the simulation and study of the kinetics of morphological evolution in nanostructured materials that will complement the development of a new undergraduate textbook on Kinetics and Phase Transformations for Materials Science.