A High-Throughput Computational and Experimental Approach to the Design of Multi-Principal Element Alloys

摘要为了满足下一代高性能运输和能源系统的设计要求，需要发现和开发具有最佳性能组合的新型金属材料。从历史上看，金属合金的发展集中在用一种主要元素（如铝或钛）修改合金，加入少量其他元素。这种策略忽略了由几种元素大致相等组成的合金所代表的巨大设计空间。由于在这个设计空间中存在数百万种组合，因此使用传统的试错方法来确定感兴趣的特定组合将非常耗时且昂贵。需要一种快速和廉价的方法来有效地筛选可能的候选组合物。该项目使用计算机模拟来识别具有改善性能潜力的元素组合，然后仅制造最有希望的组合以供进一步考虑。为了进一步降低成本，一种先进的基于3D打印的合成方法被用于构建由大约100种不同成分组成的紧凑材料库。合金库的建造在几分钟内完成，只使用了几克材料。筛选库以确定具有强度、密度、成本或其他性能最佳组合的特定组合物。这种“高通量”的金属合金设计方法将大大提高效率，降低发现和优化新型高性能金属材料所需的成本。此外，该项目将有助于培养在计算和高效制造方法方面受过培训的科学和工程劳动力，并通过针对不同学区的初中和高中教师的讲习班影响K-12科学和工程教育。技术摘要：为了满足下一代高性能运输系统、发电机和储能设备的设计要求，需要发现和开发具有增强性能的新型结构合金。多主元素合金（mpea）由几种组成元素组成，但没有主要的溶剂种类，由于传统合金设计方法的耗时性，它代表了广阔的设计空间。该合作项目的目的是利用高通量方法研究化学成分对以BCC相为主的mpea的相稳定性和力学性能的作用。该项目整合了第一性原理密度泛函理论（DFT）计算和最先进的激光沉积合成技术，以快速发现具有理想强度、密度、熔化温度和成本组合的mpea。利用像差校正扫描透射电子显微镜成像和光谱学对其局部结构进行了表征，并结合DFT计算阐明了构型熵、混合焓、晶格应变等因素对相稳定性的影响。利用纳米压痕和其他微力学方法表征了力学性能随成分的变化，并将其与结构相关联，以建立适当的结构-性能模型。具有最有希望的微尺度性能的合金将被批量制备，用于进一步分析和模型验证。通过在多组分设计空间的全部范围内进行快速评估，该项目有可能加深科学界对这些复杂合金的理解，并确定具有大大改进和意想不到的性能组合的新材料。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。

Non-technical AbstractMeeting the design requirements of the next generation of high performance transportation and energy systems requires the discovery and development of new metallic materials with optimal combinations of properties. Historically, the development of metallic alloys has focused on modifying alloys with one dominant element, such as aluminum or titanium, by adding small percentages of other elements. This strategy neglects the vast design space represented by alloys consisting of several elements in roughly equal fractions. Because many millions of combinations exist within this design space, identifying specific compositions of interest using conventional trial-and-error approaches to alloy development would be very time-consuming and expensive. A rapid and inexpensive method for efficiently screening the possible candidate compositions is required. This project uses computer simulations to identify combinations of elements with the potential for improved properties, and then manufactures only the most promising combinations for further consideration. To further reduce costs, an advanced 3D printing-based synthesis method is used to construct compact material libraries consisting of approximately 100 distinct compositions. The alloy library construction is accomplished in minutes, using only a few grams of material. The libraries are screened to identify the specific compositions with the best combinations of strength, density, cost, or other properties. This 'high-throughput' approach to metal alloy design will dramatically increase efficiency and reduce the cost required to discover and optimize new high performance metallic materials. Furthermore, the project will contribute to development of a science and engineering workforce trained in computational and efficient manufacturing methods, as well as impact K-12 science and engineering education through workshops targeting middle and high school teachers from diverse school districts.Technical AbstractMeeting the design requirements of the next generation of high performance transportation systems, power generators, and energy storage devices requires the discovery and development of new structural alloys with enhanced properties. Multi-principal element alloys (MPEAs), consisting of several constituent elements but no dominant solvent species, represent a vast yet under-explored design space due to the time-consuming nature of traditional alloy design methods. The objective of this collaborative project is to investigate the role of chemical composition on the phase-stability and mechanical properties of MPEAs having a dominant BCC phase using a high-throughput approach. The project integrates first-principles density-functional theory (DFT) calculations and state-of-the-art laser deposition-based synthesis to rapidly discover MPEAs with desirable combinations of strength, density, melting temperature, and cost. The local structure is characterized using aberration-corrected scanning transmission electron microscope imaging and spectroscopy, which are combined with DFT calculations to elucidate the roles of configurational entropy, mixing enthalpy, lattice strains and other factors on phase stability. Variations in the mechanical properties with composition are characterized using nanoindentation and other micromechanical methods and correlated with the structure in order to develop appropriate structure-property models. Alloys with the most promising microscale properties will be prepared in bulk for further analysis and model validation. By enabling rapid evaluation over the full breadth of the multicomponent design space, the project has the potential to deepen the scientific community's understanding of these complex alloys and identify new materials with vastly improved and unexpected combinations of properties.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.