CAREER: Order-induced heterogeneities in the deformation behavior of FCC concentrated solid solutions

该奖项全部或部分由2021年美国救援计划法案（公法117-2）资助。非技术性摘要实现新的更强的材料是新兴技术在民用基础设施、汽车和航空航天等各种应用领域取得成功的关键因素。例如，电动车辆的范围可以用更强的合金（即，金属和添加剂的混合物），通过实现较低重量的车辆部件而不损害乘客安全。提高强度的一个关键途径是通过理解合金如何变形（即，响应加载）。传统的理解强调添加剂化学和浓度在定向变形中的重要性。然而，这种理论在解释具有异常大浓度添加剂的合金的行为方面存在缺陷。这些浓缩合金包括许多技术上重要的材料，如高强度钢。为了解决这些缺点，这项研究工作探讨了以下问题：如何原子级组织的添加剂在集中的合金影响合金如何弯曲？这个问题的动机是假设，除了化学和浓度，添加剂组织在指导弯曲中发挥重要和未被认识到的作用。为了揭示这种联系，最前沿的机械测试技术和计算模型的开发和使用。除了推进材料测试工具外，这项工作还为这些特殊类别的合金如何弯曲提供了新的基本见解，为工程材料提供了基础性的理解，提高了强度。更广泛地说，这一努力的成果提供了关键的数据集和方法，使研究界能够进行新的调查，并有助于美国先进制造业的竞争优势。这些发现是基于虚拟现实的本科教育学习材料的基础，以及初中和高中的推广。这些教学活动的目标是通过利用虚拟现实（VR）作为向广大学生传达材料科学概念的工具，扩大对科学，技术，工程和数学（STEM）的参与。这些活动的另一个预期成果是招募学生，包括来自代表性不足群体的学生，参加这项工作的研究任务，从而加强STEM管道。  技术摘要本研究的重点是以下问题：溶质组织的长度尺度如何驱动浓固溶体的变形行为？在集中系统的背景下，这种努力的动机是观察到的溶质势能的波动，出现在位错的长度尺度。这些波动支撑了本研究的中心假设-即，化学短程有序引起可预测的，统计的不均匀性，在势能景观的浓缩固溶体，影响各种变形机制之间的竞争。为了回答上述问题，正在开发和利用补充实验（包括纳米弯曲测试技术）和计算研究工具（如尺度桥接动力学蒙特卡罗模拟）。面心立方CrCoNi系统被选为本调查的基准，但该方法可以推广到其他集中系统的科学和技术的利益。具体成果包括：1）利用化学有序作为结构参数绘制机制竞争趋势的形变机制图; 2）将化学短程有序与形变过程势能垒中长度尺度分辨涨落联系起来的统计关系;以及3）一种新的测量中尺度变形的实验-计算方法，其弥合了模拟与理论之间的时间和空间差距。更广泛地说，这项工作的成果为研究界提供了新的工具，以探索复杂合金中的多尺度关系，以及验证原子间相互作用势的关键实验数据集。教育和推广活动的特点是虚拟现实（VR）模块，以说明原子堆积，固溶体形成和滑移等概念。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Non-technical SummaryThe realization of new, stronger materials is a critical element to the success of emerging technologies in a diverse set of application areas including civil infrastructure, automotive, and aerospace. For example, the ranges of electric vehicles can be improved with stronger alloys (i.e., mixtures of metals and additives), by enabling lower weight vehicle components without a compromise to passenger safety. One key pathway to improving strength is through an understanding of how alloys deform (i.e., respond to loading). Traditional understanding emphasizes the importance of additive chemistry and concentration in directing deformation. However, this rationale has shortcomings in explaining the behavior of alloys with unusually large concentrations of additives. These concentrated alloys include many technologically important materials such as high strength steels. To address these shortcomings, this research effort explores the following question: How does the atomic-scale organization of additives in concentrated alloys influence how the alloy bends? This question is motivated by the hypothesis that, in addition to chemistry and concentration, the additive organization play an important and under-recognized role in directing bending. To reveal this link, forefront mechanical testing techniques and computational models are developed and used. In addition to advancing tools for materials testing, this effort provides new fundamental insights for how these special class of alloys bend, that provides a foundational understanding to engineer materials with improved strength. More broadly, the outcomes of this effort deliver key datasets and methodologies, which enable new investigations within the research community, and contribute to the competitive advantage of America’s advanced manufacturing industries. These findings are the basis of virtual reality-based learning materials for undergraduate education, and middle- and high-school outreach. The objective of these instructional activities is to broaden participation in science, technology, engineering and mathematics (STEM) by leveraging virtual reality (VR) as a tool to convey materials scientific concepts to a broad range of students. Another intended outcome of these activities is the recruitment of students, including those from underrepresented groups, to participate in the research tasks of this effort, and thereby enhance the STEM pipeline.  Technical SummaryThe research focuses on the following question: How does the length scale of solute organization drive the deformation behavior of concentrated solid solutions? Within the context of concentrated systems, the motivation for this effort is the observed fluctuations in solute potential energies that emerge at the length scale of dislocations. These fluctuations underpin the central hypothesis of this investigation – that is, chemical short-range order gives rise to predictable, statistical heterogeneities in the potential energy landscape of concentrated solid solutions that influence the competition between various deformation mechanisms. To answer the question above, complementary experimental, including a nanobending testing technique, and computational research tools, such as scale-bridging kinetic Monte Carlo simulation, are being developed and utilized. The face-centered cubic CrCoNi system is selected as a benchmark for this investigation, yet the approach can be generalized to other concentrated systems of scientific and technological interest. Specific outcomes from this effort include 1) deformation mechanism maps that chart the trends in mechanism competition using chemical ordering as a structural parameter; 2) statistical relationships that link chemical short-range order with the length scale-resolved fluctuations in the potential energy barriers of deformation processes; and 3) a new experimental-computational approach to measure mesoscale deformation that bridges the temporal and spatial gap between simulations and theory. More broadly, the outcomes of this effort provide the research community with new tools to explore multiscale relationships in complex alloys, and key experimental datasets to validate interatomic potentials. The education and outreach activities feature virtual reality (VR) modules in order to illustrate concepts such as atomic packing, solid solution formation and slip.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.