Experimental and Theoretical Investigations of Gum Metal

胶质金属的实验和理论研究

• 批准号: 1105081
• 负责人: Daryl Chrzan
• 金额: $ 42万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1105081&HistoricalAwards=false
• 关键词: Experimental; Theoretical; Investigations; Gum; Metal

TECHNICAL SUMMARY: Gum metals are Ti-Nb based alloys that display remarkable mechanical properties, including super-elasticity, super-strength, large ductility, zero coefficient of thermal expansion and elastic constants that remain constant over a range of temperatures. Surprisingly, plasticity in these materials appears to be mediated neither by dislocation motion nor by phase transformation. Instead, these materials appear to deform at their ideal strength. If so, these alloys represent a new type of structural alloy. Their unusual mechanical behavior is linked to a strong elastic anisotropy that develops as the composition of the alloy is driven towards a phase transformation. This anisotropy allows for easy dislocation pinning, the extreme spreading of the dislocation cores, and plays a role in the suppression of phase transformations that might otherwise weaken the alloys. The project involves two primary goals. First it aims to understand experimentally the precise mechanism governing plasticity in these unusual alloys. This understanding will be developed using a combination of nanoindentation and transmission electron microscopy experiments. Second, the project will develop theoretical tools and ideas capable of explaining the observed deformation behavior. Initial theoretical studies will focus on the structure of dislocations within Gum Metals paying particular attention to the implications of spread dislocation cores and dislocation core overlap. The understanding so obtained will be used to identify new alloys systems with the potential to deform similarly to Gum Metals.NON-TECHNICAL SUMMARY: The ideal strength of a material is the largest possible load the material can withstand before becoming permanently deformed. Typically, the observed strength of a material is 1/100th or less of its ideal strength, largely because defects known as dislocations are able to move throughout the crystal at stresses well below the ideal strength. This understanding lies at the heart of modern metallurgy, and guides the development of most structural alloys. Gum Metal is a recently discovered Ti-Nb based alloy with a long list of remarkable mechanical properties. The most striking characteristic is that Gum Metal appears to deform at ideal strength via a unique dislocation-free deformation mechanism. The goal of this research is to identify and understand the deformation mechanism(s) that gives rise to the remarkable properties of Gum Metal, and to use this understanding to develop the metallurgical principles that govern Gum Metal behavior. These principles will then be used to search for new materials that display mechanical properties similar to Gum Metal. The identification of novel metallurgical principles has the potential to enable the development of a new class of structural materials. Such materials would impact a broad range of technologies including transportation and energy generation. Students working towards their doctoral degrees will conduct much of the research. Course materials geared toward introducing high school physics students to the discipline of materials science and engineering will be developed and exemplified by the role of structural materials in the sport of skateboarding---a sport popular with teenagers.

技术摘要：橡胶金属是钛铌基合金，具有卓越的机械性能，包括超弹性、超强度、大延展性、零热膨胀系数以及在一定温度范围内保持恒定的弹性常数。 令人惊讶的是，这些材料的塑性似乎既不是由位错运动也不是由相变介导的。 相反，这些材料似乎会在理想强度下变形。 如果是这样，这些合金代表了一种新型结构合金。它们不寻常的机械行为与强弹性各向异性有关，这种各向异性是随着合金成分发生相变而产生的。 这种各向异性使得位错钉扎变得容易，位错核极度扩散，并在抑制相变方面发挥作用，否则相变可能会削弱合金。该项目涉及两个主要目标。 首先，它的目的是通过实验了解控制这些不寻常合金可塑性的精确机制。 这种理解将通过纳米压痕和透射电子显微镜实验的结合来发展。 其次，该项目将开发能够解释观察到的变形行为的理论工具和想法。 最初的理论研究将集中于橡胶金属内的位错结构，特别关注扩散位错核心和位错核心重叠的影响。如此获得的理解将用于识别具有与橡胶金属类似的变形潜力的新合金系统。非技术摘要：材料的理想强度是材料在永久变形之前可以承受的最大可能载荷。通常，观察到的材料强度为其理想强度的 1/100 或更低，这主要是因为位错缺陷能够在远低于理想强度的应力下在整个晶体中移动。 这种理解是现代冶金学的核心，并指导着大多数结构合金的开发。 Gum Metal 是一种最近发现的 Ti-Nb 基合金，具有一系列卓越的机械性能。最显着的特征是，橡胶金属似乎通过独特的无位错变形机制以理想的强度变形。 这项研究的目标是识别和理解产生橡胶金属卓越性能的变形机制，并利用这种理解来开发控制橡胶金属行为的冶金原理。 然后，这些原理将用于寻找具有与橡胶金属相似的机械性能的新材料。 新型冶金原理的确定有可能开发出新型结构材料。此类材料将影响包括运输和能源生产在内的广泛技术。 攻读博士学位的学生将进行大部分研究。旨在向高中物理学生介绍材料科学与工程学科的课程材料将通过结构材料在滑板运动（一项深受青少年欢迎的运动）中的作用来开发和举例说明。