Understanding the Fundamental Deformation Processes of BCC Refractory High Entropy Alloys using Experimentally-Validated Kinetic Monte Carlo Simulations

使用经过实验验证的动力学蒙特卡罗模拟了解 BCC 难熔高熵合金的基本变形过程

• 批准号: 1905822
• 负责人: Jaime Marian
• 金额: $ 43.21万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1905822&HistoricalAwards=false
• 关键词: Understanding; Fundamental; Deformation; Processes; BCC

NON-TECHNICAL SUMMARY:Developing new materials is at the heart of technology advancements such as cellphones, earthquake-resistant structures, or advanced satellites and space probes. One area where new materials are sorely needed is that of energy generation based on standard steam cycles. There, one way to reduce greenhouse gas emissions is to increase the thermodynamic efficiency of the plants. This can be done by developing materials that can sustain higher operating temperatures than the current standard set by nickel-based superalloys. High-entropy alloys are one such class of materials that hold the promise of increasing the operating temperature by up to 300~500 degrees. High-entropy alloys are made up of four or more chemical elements (specifically transition metal elements) in equal proportions, and thus have a very complex chemistry. This project focuses on understanding the deformation behavior and strength of these alloys at high temperatures using the most advanced computational and experimental tools at the atomic scale. The goal is to discover the mechanisms that make these systems strong at high temperature so that we can design yet better alloys and use them to replace current materials in power generation plants to increase their efficiency. For this, a diverse group of students and scientists will be engaged, including women, latino students from the Los Angeles area, and military veterans, which bring discipline, focus, and familiarity with high-precision machinery and computers. This project will be able to advance our goals towards reducing the carbon footprint of existing power plants, and contribute to other applications such as improved jet and rocket engines and safer nuclear power plants. TECHNICAL SUMMARY:Refractory high entropy alloys (RHEA) are a class of materials consisting of four or more refractory metal elements in equiatomic proportions. These alloys show great promise for high temperature applications due to their high strength and ductility in a wide temperature range, potentially superior to even Ni-based superalloys. These systems usually crystallize in a body-centered cubic (bcc) alloy, which suggests that their plastic response is controlled by thermally activated motion of screw dislocations. However, the high strength of these systems at high temperature does not fit standard theories of lattice resistance and solid solution hardening. In this project, a kinetic Monte Carlo (kMC) model of screw dislocation glide will be developed. The alloy will be represented as an effective medium characterized by an atomic averaging of all the alloy elements, and where each atom then is treated as a solute in this effective environment. The project focuses on the NbMoTaW system as a representative RHEA. The computational approaches will be validated using in-situ transmission electron microscopy nanomechanical tests of single-crystal specimens, which will be used to study the temperature, orientation and strain rate dependence of the alloy. Ultimately, the tools developed under this proposal will be useful to assess how refractory high entropy alloys deform as a function of temperature and strain rate, with the goal of improving the high temperature behavior of these systems and evaluating their potential to increase the efficiency of power plants. The proposal contains a plan to involve both undergraduate students and students of underrepresented minorities in the research activities. As well, the proposal investigators will reach out to minority students and Armed Forces veterans pursuing undergraduate degrees in science and engineering. The results of this proposal will be used to enhance the content of several courses at UCLA where dislocations, strengthening mechanisms, and metals plasticity are a central part of the syllabus.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.

非技术摘要：开发新材料是技术进步的核心，例如手机，抗震结构或先进的卫星和太空探针。迫切需要新材料的一个区域是基于标准蒸汽循环的能源发电。在那里，减少温室气体排放的一种方法是提高植物的热力学效率。这可以通过开发可以维持比基于镍的Superalloys设定的当前标准的材料来完成。高渗透合金是一种这样的材料，具有将工作温度提高300〜500度的承诺。高渗透合金由相等比例的四个或多个化学元件（特别是过渡金属元件）组成，因此具有非常复杂的化学作用。该项目的重点是使用原子规模上最先进的计算和实验工具在高温下在高温下的变形行为和强度。目的是发现使这些系统在高温下强大的机制，以便我们可以设计出更好的合金并使用它们来代替发电厂中的当前材料以提高其效率。为此，将订婚一群学生和科学家，包括妇女，洛杉矶地区的拉丁裔学生和退伍军人，这些学生对高精度的机械和计算机带来了纪律，重点和熟悉。该项目将能够促进我们的目标，以减少现有发电厂的碳足迹，并为其他应用做出贡献，例如改善的喷气式和火箭发动机以及更安全的核电站。 技术摘要：难治性的高熵合金（RHEA）是一类材料，由四个或更多的耐火金属元素组成，分别是等值的。这些合金在宽温度范围内的高强度和延展性，对高温应用显示出巨大的希望，甚至可能优于基于NI的超合金。这些系统通常以身体为中心的立方（BCC）合金结晶，这表明它们的塑料响应是通过螺钉位错的热激活运动控制的。但是，这些系统在高温下的高强度不符合晶格耐药性和实心溶液硬化的标准理论。在这个项目中，将开发螺钉脱位滑行的动力学蒙特卡洛（KMC）模型。合金将被表示为有效培养基，其特征是所有合金元素的原子平均值，然后在这种有效环境中将每个原子视为溶质。该项目专注于NBMOTAW系统作为代表性RheA。计算方法将使用原位传输电子显微镜纳米力学测试进行验证，该测试将用于研究合金的温度，方向和应变速率依赖性。最终，根据该提案开发的工具将有助于评估难治性高熵合金如何随温度和应变速率变形，目的是改善这些系统的高温行为并评估它们提高功率效率的潜力植物。该提案包含一项计划，涉及本科生和代表性不足的少数群体的学生参与研究活动。同样，提案调查人员还将与攻读科学和工程学学位的少数族裔学生和武装部队退伍军人接触。该提案的结果将用于增强UCLA上多个课程的内容，在该课程中，位错，加强机制和金属可塑性是教学大纲的核心部分。该奖项反映了NSF的法定任务，并被认为是通过使用评估的支持值得的。基金会的智力优点和更广泛的影响审查标准。

项目成果

Cross-kinks control screw dislocation strength in equiatomic bcc refractory alloys

• DOI: 10.1016/j.actamat.2021.116875
• 发表时间: 2021-04
• 期刊: Acta Materialia
• 影响因子: 9.4
• 作者: Xinran Zhou;Sicong He;J. Marian

Microscale deformation controlled by compositional fluctuations in equiatomic Nb–Mo–Ta–W alloys

等原子 Nb-Mo-Ta-W 合金成分波动控制的微尺度变形

• DOI: 10.1016/j.msea.2022.143892
• 发表时间: 2022
• 期刊: Materials Science and Engineering: A
• 作者: Pozuelo, Marta;Marian, Jaime
• 通讯作者: Marian, Jaime