Theoretical and Experimental Investigations of Gum Metal

技术：pi将追求一个变革性的研究计划，详细研究最近发现的一类Ti-Nb合金的机械性能，称为胶金属。胶金属表现出超弹性、高强度和显著的延展性，这些都是在没有传统的、位错介导的塑性的情况下。在先前由NSF NIRT资助（部分）的一项工作中，pi已经对这些材料的机械性能进行了初步分析。具体来说，pi已经证明树胶金属在其理想强度极限附近变形。此外，pi表明，即使在接近理想强度的应力下，位错也很容易被钉住。通过纳米压痕实验，pi表明材料通过（明显）纳米尺度体积元的连续旋转而变形。所有这些性质都与电子填充引起的从体心立方到六边形紧密堆积结构的转变有关。pi将在两个方向上大大扩展他们对胶金属行为的先前研究。首先，pi将对树胶金属的机械性能有更详细的了解。这些研究将扩展到包括位错核心的研究，以及与纳米压痕相关的纳米级变形模式的更详细的映射。pi将使用理论来识别新的合金，这些合金是口香糖金属行为的候选者。pi将以薄膜形式合成合金并直接探索其力学性能。非技术：胶金属的行为为材料理论家和冶金学家提供了几个令人兴奋的机会。由于这些材料的力学性能与可以使用最好的基于总能量的量子力学方法直接计算的数量有关，因此这些合金的快速，计算机辅助的高级工程确实有机会。此外，理论将用于确定胶金属行为的其他候选者。pi的工作旨在利用这些机会，它将促进对胶质金属行为的理解，更广泛地说，是对冶金可能性的理解。该项目将在许多方面产生广泛的影响。首先，将有两名研究生直接参与这个项目，他们在这个项目中进行的研究将推进他们的博士学位。每位学生都将被鼓励撰写论文，并参加专业协会的会议，以传播他们的研究成果。其次，研究成果将直接纳入伯克利分校研究生水平的计算材料科学课程。第三，pi将招募本科生参与该项目，利用伯克利旨在吸引代表性不足群体学生参与研究的项目。从更广泛的角度来看，具有与80年来冶金智慧相冲突的机械性能的合金的存在确实令人兴奋。先进材料工程的潜力是显而易见的。该研究计划可能会导致具有“超级”性能和许多技术应用的广泛的新型合金。

TECHNICAL: PIs will pursue a transformative research program to study in detail the mechanical properties of the recently discovered class of Ti-Nb alloys known as Gum Metals. Gum Metals display super-elasticity, high strength, and significant ductility all in the absence of traditional, dislocation mediated plasticity. In an effort previously funded (in part) through an NSF NIRT, PIs have conducted a rudimentary analysis of the mechanical properties of these materials. Specifically, PIs have demonstrated that Gum Metals are deforming near their ideal strength limit. Further, PIs demonstrated that the dislocations may be pinned easily, even at stresses approaching the ideal strength. Using nanoindentation experiments, PIs showed that the material deforms through (apparently) continuous rotations of nanoscale volume elements. All of these properties have been linked to an electron-filling-induced transition from a body-centered cubic to a hexagonal close packed structure. PIs will expand substantially their prior investigations of Gum Metal behavior in two directions. First, PIs will develop a more detailed understanding of the mechanical properties of Gum Metals. These studies will expand to include the study of dislocation cores, as well as more detailed mapping of the nanoscale deformation patterns associated with nanoindentation. PIs will use theory to identify new alloys that are candidates for Gum Metal behavior. PIs will synthesize the alloys in thin film form and explore directly their mechanical properties. NON-TECHNICAL: Gum Metal behavior presents several exciting opportunities for materials theorists and metallurgists. Since the mechanical properties of these materials are linked to quantities that can be computed directly using the best available quantum mechanical based total energy methods, there is a genuine opportunity for rapid, computer aided, advanced engineering of these alloys. Further, theory will be used to identify other candidates for Gum Metal behavior. PIs' work is aimed at exploiting these opportunities, and it will advance the understanding of Gum Metal behavior and, more generally, an understanding of metallurgical possibilities. The project will have a broad impact in a number of ways. First, there will be two graduate students working directly on the project, and their research conducted within this program will advance their Ph.D. studies. Each student will be encouraged to write papers and to attend meetings of professional societies in order to disseminate their research results. Second, the research results will be incorporated directly into the graduate level Computational Materials Science course taught at Berkeley. Third, the PIs will recruit undergraduates to work on the project using programs at Berkeley aimed at engaging students from underrepresented groups in research. Within a much broader perspective, the existence of alloys with mechanical properties that conflict with 80 years of metallurgical wisdom is truly exciting. The potential for the engineering of advanced materials is clear. The research program may lead to a broad new class of alloys with "super" properties and numerous technological applications.