Understanding the Hardening Mechanisms Associated with Short-Range Atom Clusters in High Entropy Alloys

非技术总结该奖项支持金属材料力学行为的理论和计算研究和教育。金属和合金是制造业和结构应用的主力材料。这主要是因为它们具有良好的强度平衡，金属对变形和破坏的抵抗力，以及延展性，即金属在断裂前经历不可逆变形的能力。通常存在强度和延性之间的权衡，材料的强度增加不可避免地伴随着延性的牺牲。高熵合金是一类新的材料，它含有五种或五种以上不同元素的几乎相同数量的原子。其非传统的多元素集中成分有望实现强度和延展性的非凡组合。然而，控制高熵合金强度和延展性的基本机制在很大程度上还没有被探索出来。本课题主要研究高熵合金的微观变形机制。成分波动对合金中原子周期性排列缺陷所引起的变形过程的影响将通过原子尺度上的计算机模拟来研究；结果将进一步与实验相比较。所获得的物理见解将对指导具有优异强度-塑性组合的新型高熵合金的未来发展具有重要意义。该项目将促进理论和实验之间的合作。教育活动将提供机会向学生介绍模拟材料的计算机建模技术，并激励学生追求科学和工程方面的职业。技术总结该奖项支持理论和计算研究和教育，以促进对高熵合金变形机制的基本理解。强度和延展性是工程应用中金属和合金最重要的机械性能之一。高熵合金含有接近等原子比例的五种或五种以上不同元素的高浓度。控制高熵合金强度和塑性的机制仍然知之甚少。本项目致力于了解短程团簇在面心立方高熵合金应变硬化和拉伸塑性中的作用机制。多组分原子间相互作用势将被用来进行分子动力学和原子反应路径模拟，以研究由短程团簇介导的位错钉扎和交叉滑移过程。将研究应力、温度、团簇大小和密度的影响。模拟结果将与位错机制和变形微观组织的实验特征进行比较。所获得的洞察力对于利用短程团簇在高熵合金中实现优异的强度-塑性组合具有重要意义。该项目将向学生介绍先进的建模技术。研究成果将被纳入高中课程模块和微观力学研究生课程。本科生将参与这项研究。这些教育活动旨在激励学生追求科学和工程方面的职业。这一奖项反映了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。

NONTECHNICAL SUMMARYThis award supports theoretical and computational research and education on mechanical behaviors of metallic materials. Metals and alloys are the workhorse materials for the manufacturing industry and structural applications. This is mainly because they have a good balance of strength, a metal's resistance to deformation and failure, and ductility, a metal's ability to undergo irreversible deformation before rupture. Usually there is a strength-ductility tradeoff, a gain in strength in a material is inevitably accompanied by a sacrifice in ductility. High entropy alloys are a new class of materials that contain nearly equal numbers of atoms of five or more different elements. Their unconventional concentrated multiple element compositions hold promise for achieving an exceptional combination of strength and ductility. However, the fundamental mechanisms that control the strength and ductility in high entropy alloys down to the atomic scale remain largely unexplored. This project focuses on investigation of the microscopic deformation mechanisms in high entropy alloys. Effects of the composition fluctuations on deformation processes mediated by defects in the periodic arrangement of atoms in the alloy will be studied by computer simulations on the scale of atoms; the results will be further compared with experiments. The physical insights gained will be important for guiding the future development of new high entropy alloys with a superior strength-ductility combination. The project will foster collaborations between theory and experiment. Educational activities will offer opportunities to introduce students to computer modeling techniques for simulating materials and to inspire students to pursue careers in science and engineering.TECHNICAL SUMMARYThis award supports theoretical and computational research and education to advance the fundamental understanding of deformation mechanisms in high entropy alloys. Strength and ductility are among the most important mechanical properties of metals and alloys for engineering applications. High entropy alloys contain high concentrations of five or more different elements in near equiatomic proportions. The mechanisms controlling the strength and ductility of high entropy alloys remain poorly understood. This project is focused on understanding the mechanistic role of short-range clusters in the strain hardening and tensile ductility of face-centered cubic high entropy alloys. Multi-component interatomic potentials will be used to perform molecular dynamics and atomistic reaction pathway simulations for studying the dislocation pinning and cross-slip processes mediated by short-range clusters. Effects of stress, temperature, cluster size and density will be investigated. The modeling results will be compared with experimental characterizations of dislocation mechanisms and deformation microstructures. The insights gained are important for harnessing the short-range clusters to achieve a superior strength-ductility combination in high entropy alloys. The project will introduce advanced modeling techniques to students. The research results will be incorporated into a high-school course module as well as a graduate course on micromechanics. Undergraduate students will be involved in the research. These educational activities are aimed to inspire students to pursue careers in science and engineering.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.