Collaborative Research: Deformation Mechanisms in Microstructurally Tailored High Strength Alloys Near the Ideal Limit

非技术描述：强度越来越高的材料通常是材料科学家用于结构工程应用的目标--更坚固的材料使结构更安全，重量更轻，从而更节能地运输。有几种途径可以通过控制材料中的缺陷来提高强度。然而，迄今为止的努力未能使物质力量接近强化的圣杯，也就是所谓的理想力量。这一失败并不是因为缺乏材料工程，材料设计或加工方面的创新也不能立即解决问题。相反，从材料变形物理的角度来看，以前的方法在范围上过于有限，本研究通过考虑控制材料结构的新设计路径来解决这一问题，进而控制强度的缺陷。该项目的发现适用于化学复杂性增加的先进材料，这是现代工程应用所需的。正在开发一种超越传统机构障碍的交互式在线学习模块--工程教育中的力学互动团队(MINT)倡议--以使合作大学的学生与专注于材料科学尖端主题的新虚拟学习模块合作。通过与加州大学欧文分校高级铸造研究中心的合作，最初的研究生课程重点正在扩大到本科生，并通过与加州大学欧文分校高级铸造研究中心的合作，进一步扩大到使用相关设计问题的工作专业人员。技术描述：这项研究通过对位错成核和扩展作为纳米结构合金中的限速变形机制的基本了解，使材料具有接近理想的强度。在纳米结构合金中，缺陷约束以及与晶界和晶格溶质的相互作用是塑性的局部障碍。需要回答的具体研究问题包括：(I)在溶质修饰的界面上和在纳米合金晶体内传播的位错成核的重要过渡态和相关的能垒是什么，(Ii)界面结构和掺杂后的能量变化如何改变位错的成核/传播，以及(Iii)晶内溶质原子如何影响位错的传播，这些原子可能成为局部钉扎点，但也改变了晶格的性质？这项研究的一个实用假设是，通过协同掺杂来稳定晶界以防止局部塑性和延迟缺陷形核，同时抑制位错通过纳米晶内部的扩展，可以最大限度地提高纳米晶合金的强度。利用原子模拟、多模式结构表征和独特的微观机械测试相结合的方法，这一假说正在纳米结构的铝和铜合金中得到验证，它们本质上不同的层错能量将提供不同的受限滑移事件。从广义上讲，这项研究将在纳米工程金属材料中定义新的强化范式，并建立溶质偏向界面能景观的机制基础，以了解受限滑移环境中的基本位错物理。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL DESCRIPTION: Materials with higher and higher strengths are often the target of materials scientists for structural engineering applications – stronger materials enable safer structures as well as lightweighting for more energy-efficient transportation. Several pathways are available for enhancing strength through control over defects in the material. However, efforts to-date have failed to bring material strengths anywhere near the holy grail of strengthening, referred to as the ideal strength. This failure has not come from a lack of materials engineering, nor would innovations in materials design or processing immediately solve the problem. Instead, prior approaches have been too limited in scope from the viewpoint of the material’s deformation physics, which is addressed in this research by considering novel design pathways for controlling material structure and, in turn, the defects that govern strength. The findings of this project are applicable to advanced materials with increased chemical complexity, which are desired for modern engineering applications. An interactive online learning module transcending traditional institutional barriers – denoted the Mechanics Interactive Teaming (MINT) initiative in engineering education – is being developed to engage students cooperatively at the partnering universities with new virtual learning modules focused on cutting-edge topics in materials science. The initial focus on graduate curricula is being broadened to reach undergraduates through the Women in Science and Engineering Program at Stony Brook University and further expanded for working professionals using relevant design problems through collaboration with the Advanced Casting Research Center at UC Irvine.TECHNICAL DESCRIPTION: This research enables materials with near-ideal strength by developing a fundamental understanding of dislocation nucleation and propagation as rate-limiting deformation mechanisms in nanostructured alloys where defect confinement and interaction with grain boundary and lattice solutes act as local barriers to plasticity. Specific research questions to be answered include: (i) what are the important transition states and associated energy barriers for dislocation nucleation at solute-decorated interfaces and for propagation within a nanoscale alloy crystal, (ii) how does interfacial structure and energy variation upon doping alter dislocation nucleation/propagation, and (iii) how do solute atoms inside the grain, which can potentially act as local pinning points but also alter the properties of the lattice, influence dislocation propagation? A practical hypothesis of this research is that the strength of nanocrystalline alloys can be maximized by synergistic doping to stabilize the grain boundaries against local plasticity and delay defect nucleation while simultaneously inhibiting dislocation propagation through the nanograin interiors. Using a combination of atomistic modeling, multi-modal structural characterization, and unique micromechanical testing, this hypothesis is being tested in nanostructured aluminum and copper alloys, where their intrinsically different stacking fault energies will provide access to different confined slip events. In a broad sense, this research will define new strengthening paradigms in nanoengineered metallic materials and establish the mechanistic underpinnings of solute-biased interfacial energy landscapes for understanding fundamental dislocation physics in confined slip environments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.