High entropy effects from variable chemical order in multi-principal element solution alloys

多主元素溶液合金中可变化学顺序的高熵效应

• 批准号: 1804320
• 负责人: Mingwei Chen
• 金额: $ 40.2万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1804320&HistoricalAwards=false
• 关键词: entropy; effects; variable; chemical; order

Non-technical Abstract:This project advances the field by answering a fundamental materials science question, the structure (in this case, the local chemical order, LCO)-property relationship in the emerging high entropy alloys (HEAs, where multiple elements are mixed in equal amounts and the resulting alloy retains a single atomic structure). The focus is on the signature 'high entropy effect' that sets these HEAs apart from traditional solid solutions. The research highlights the wide variety of local chemical order on the atomic-to-nanometer level and therefore 'plenty of room at the bottom' for rich property possibilities. It will also deliver a powerful toolset (realistic interaction potentials) for the atomistic modeling community working on HEAs to gain atomistic insight into the underlying deformation mechanisms. This work also offers niche benefits for society and education. First, from the application standpoint, the LCOs in HEAs open a vast playground to tailored properties in solution alloys. For example, a random solution is amenable to extensive shaping at room temperature. After shaping, the part can be heated to an intermediate temperature to develop LCO over an extended period of time, gaining strength for load-bearing applications. Second, this research will improve the understanding of closely-related concentrated alloys, such as the very popular stainless steels. Third, the new alloys with partial chemical order will enrich the basic courses in materials science, such as Thermodynamics and Phase Transformations, so that future students can practice a real-world example of 'solution' in their hands, one that can be manipulated to go all the way from chemically random to highly ordered, and see for themselves what various enthalpy and entropy terms do to the starting random solution. The findings of new alloys and new properties will be broadly disseminated at international conferences and in first-class journals.Technical Abstract:Configurational entropy has been perceived as the key factor in stabilizing multi-principal element single-phase solid solutions (SS), the so-called "high entropy alloys" (HEAs). However, the role of entropy in phase selection was overrated, as these concentrated alloys have complex chemical interactions, such that the random SS is only metastable except at very high temperatures. The goal of this project is to highlight a hitherto less-noticed, and arguably more important, trait of 'high entropy', and illustrate its impact on the defect behavior and mechanical properties. It will be illustrated that HEAs are not really chemically disordered, but rather have large variability of local chemical order (LCO) of the various species on the lattice sites. This, while precluding the hypothetical extreme of ideal random solution, represents a vast range of possible structural arrangements that can be tailored to change HEA properties, beyond traditional solutions and intermetallics. Molecular dynamics simulations will be conducted with realistic empirical interatomic potentials developed specifically for HEAs, to systematically i) map out the LCOs possible in HEA at a given composition and its strong dependence on the processing temperature; ii) demonstrate that the partial chemical order sensitively and drastically changes generalized planar fault energy, not only in terms of its sample-average, but also its spatial variation; and iii) unveil how the different LCOs influence the behavior of dislocation, in particular its energy landscape and the activation parameters that govern the mechanical strength.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.

摘要：该项目通过回答一个基本的材料科学问题，即新兴高熵合金（HEAs，多种元素等量混合，所得合金保持单一原子结构）的结构（在这种情况下，局部化学顺序，LCO）-性能关系，推动了该领域的发展。重点是将这些HEAs与传统固体解决方案区分开来的标志性“高熵效应”。这项研究强调了在原子到纳米水平上局部化学秩序的广泛多样性，因此“底部有足够的空间”来实现丰富的属性可能性。它还将为在HEAs上工作的原子建模社区提供一个强大的工具集（现实的交互潜力），以获得对潜在变形机制的原子性洞察。这项工作也为社会和教育提供了利基效益。首先，从应用的角度来看，高等教育机构中的lco为定制溶液合金的性能开辟了广阔的天地。例如，随机解在室温下可以进行广泛的整形。成型后，可以将零件加热到中等温度，以在较长时间内形成LCO，从而获得承载应用的强度。其次，这项研究将提高对密切相关的浓缩合金的理解，例如非常流行的不锈钢。第三，具有部分化学有序的新合金将丰富材料科学的基础课程，如热力学和相变，这样未来的学生就可以在他们手中实践一个现实世界的“溶液”例子，一个可以被操纵的“溶液”可以从化学随机到高度有序，并亲眼看到不同的焓和熵项对开始的随机溶液有什么影响。新合金和新性能的发现将在国际会议和一流期刊上广泛传播。技术摘要：构型熵被认为是稳定多主元单相固溶体（SS）的关键因素，即所谓的“高熵合金”（HEAs）。然而，熵在相选择中的作用被高估了，因为这些浓缩合金具有复杂的化学相互作用，因此随机SS除了在非常高的温度下只能是亚稳态的。该项目的目标是突出迄今为止较少注意到的，并且可以说是更重要的“高熵”特征，并说明其对缺陷行为和机械性能的影响。这将说明HEAs并不是真正的化学无序，而是在晶格位置上的不同物种的局部化学顺序（LCO）有很大的变化。这在排除理想随机溶液的假设极端的同时，代表了广泛的可能的结构安排，可以定制来改变HEA的性质，超越传统的溶液和金属间化合物。分子动力学模拟将使用专门为HEAs开发的现实经验原子间电位进行，以系统地i)绘制给定组成下HEA中可能的lco及其对加工温度的强烈依赖性；Ii)证明了局部化学阶序对广义平面断层能的敏感和剧烈变化，不仅体现在其样本平均值上，而且体现在其空间变异上；iii)揭示不同的lco如何影响位错的行为，特别是其能量格局和控制机械强度的激活参数。该奖项反映了美国国家科学基金会的法定使命，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。

项目成果

Universal scaling law of glass rheology

• DOI: 10.1038/s41563-021-01185-y
• 发表时间: 2020-08
• 期刊: Nature Materials
• 影响因子: 41.2
• 作者: Shuangxi Song;F. Zhu;Mingwei Chen

Decoupling between Shockley partials and stacking faults strengthens multiprincipal element alloys

• DOI: 10.1073/pnas.2114167118
• 发表时间: 2021-12
• 期刊: Proceedings of the National Academy of Sciences
• 作者: Zongrui Pei;Siyuan Zhang;Yinkai Lei;Fan Zhang;Mingwei Chen

Hidden Effects of Negative Stacking Fault Energies in Complex Concentrated Alloys

• DOI: 10.1103/physrevlett.126.255502
• 发表时间: 2021-06-21
• 期刊: PHYSICAL REVIEW LETTERS
• 影响因子: 8.6
• 作者: Pei, Zongrui;Dutta, Biswanath;Chen, Mingwei
• 通讯作者: Chen, Mingwei

Strengthening in multi-principal element alloys with local-chemical-order roughened dislocation pathways

• DOI: 10.1038/s41467-019-11464-7
• 发表时间: 2019-08-08
• 期刊: NATURE COMMUNICATIONS
• 影响因子: 16.6
• 作者: Li, Qing-Jie;Sheng, Howard;Ma, Evan
• 通讯作者: Ma, Evan

Unusual dislocation behavior in high-entropy alloys

• DOI: 10.1016/j.scriptamat.2020.02.021
• 发表时间: 2020-05-01
• 期刊: SCRIPTA MATERIALIA
• 影响因子: 6
• 作者: Ma, Evan