A New Experimental/Computational Approach for Predicting Phase Evolution and Defect Thermodynamics: Application to Concentrated Multicomponent Ni-Based Superalloys

预测相演化和缺陷热力学的新实验/计算方法：在浓多组分镍基高温合金中的应用

• 批准号: 0804610
• 负责人: David Seidman
• 金额: $ 59万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-06-01 至 2012-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0804610&HistoricalAwards=false
• 关键词: New; Experimental; Computational; Approach; Predicting

TECHNICAL: PIs will study temporal evolution of microstructures in concentrated Ni-based superalloys, which are used in the aviation, electric generation, chemical, and gas and oil industries. Their microstructures consist of coherent ordered gamma?(g?)-precipitates in a disordered FCC gamma(g)-matrix. There are significant unanswered questions concerning the early stage nucleation of the coherent g?-phase and phase separation from the g-matrix. Additionally, the temporal evolution of the crystallography and morphology of the g?-precipitates will be studied at all relevant length scales (micron to subnanoscale) using scanning electron, electron transmission, and high-resolution electron microscopies. In parallel with the experimental research, PIs will perform lattice kinetic Monte Carlo (LKMC) simulation, based on a vacancy diffusion mechanism, to simulate the temporal evolution of the microstructures at the same length scale as the LEAP tomograph reconstructions, where the kinetic parameters are experimental and/or calculated from first-principles density functional theory (DFT). PIs will study the kinetic pathways for nucleation in Ni-Al-Cr alloys whose mean compositions are close to the solvus line and therefore they may follow classical nucleation theory (CNT). Additionally, PIs will study two Ni-Al-Cr alloys with similar volume fractions of the g?-phase whose mean compositions are farther from the solvus line and hence less likely to obey CNT. All the experimental results are to be compared to LKMC simulation and diffusion theory. To analyze the data, a new theory of nucleation in concentrated multi-component alloys is developed that takes full advantage of a normal mode analysis to reformulate the theory of coherent phase separation that incorporates the complete details of solid-state diffusion. Additionally, PIs are exploring ways to rephrase CNT based on a diffusion equation. Finally, to make a link between the microstructure and the high-temperature mechanical properties of Ni-based superalloys PIs will calculate the Helmholtz free energy of anti-phase boundaries (APBs), sigma-APB. PIs present a new approach, the residence weight algorithm, which combines density functional calculations and Monte Carlo simulations, to calculate the APB free energy. PI?s atomic scale approach to studying the temporal evolution of microstructures is significantly different from existing methods in that PIs combine atomic-scale experimentation, simulation, and diffusion theory. The combined experimental/computational approach will allow an atomistic description that spans the subnanometer to mesoscopic length scales with unprecedented fidelity. NON-TECHNICAL: Through the Northwestern University Center for Atom-Probe Tomography (NUCAPT) PIs are educating undergraduate work-study, senior-thesis, research-experiences for undergraduate students (REU), and research experiences for teachers (RET) to perform atom-probe tomography using a LEAP tomograph. These programs have and will involve men, women and legal minority groups, Hispanic, and African-American. NUCAPT also provides APT services to other universities, national laboratories, and industrial firms. Additionally, PIs will develop a summer workshop on ?Linking Atomic-Scale Experiments and Computations,? to be held during the summer of the 2nd year of the grant at Northwestern. This course will be geared toward graduate students interested in atomic-scale and multiscale computation, and atomic-scale experimentation, as well as young faculty members and industrial participants. PIs are planning for ca. 50 participants and intend to charge a modest registration fee to cover costs.

技术：PIS将研究集中基于NI的超合金的微观结构的时间演化，这些合金用于航空，发电，化学，天然气和石油工业。它们的微观结构由连贯的有序伽马？（g？）组成 - 在FCC伽马（G）-matrix中沉淀。关于相干g？ - 相和与g矩阵的相位分离的早期成核存在明显的未解决问题。另外，将使用扫描电子，电子传输和高分辨率电子显微镜在所有相关长度尺度（微米到亚纳米级的微米）上研究晶体学和形态的时间演变。与实验研究同时，PIS将基于空置扩散机制执行晶格动力学蒙特卡洛（LKMC）模拟，以模拟微观结构的时间演化与LEAP阶级重建相同长度的时间演化，其中动力学参数是实验性和/或计算的，并且来自第一构化的函数（dfft formational doctions doctions doctions doctions doctials doctional doctional doctions dfff）。 PI将研究Ni-Al-CR合金中成核的动力学途径，其平均成分接近溶剂线，因此它们可以遵循经典成核理论（CNT）。此外，PI将研究两种ni-al-CR合金，具有相似的g？阶段的体积分数，其平均成分远离溶剂线，因此不太可能服从CNT。所有实验结果均应与LKMC模拟和扩散理论进行比较。为了分析数据，开发了浓缩多组分合金中的新成核理论，该理论可以充分利用正常模式分析，以重新制定相干相分离理论，该理论结合了固态扩散的完整细节。另外，PI正在探索基于扩散方程的重新介绍CNT的方法。最后，为了在基于Ni的Superalloys的微观结构与高温机械性能之间建立联系，PI将计算抗相物边界（APB）的Helmholtz自由能，Sigma-apb。 PI提出了一种新方法，即将密度功能计算和蒙特卡洛模拟结合的居住权重算法，以计算APB自由能。 PI的原子量表方法研究微观结构的时间演变与现有方法显着不同，因为PIS结合了原子级实验，模拟和扩散理论。合并的实验/计算方法将允许一个原子描述以前所未有的忠诚度跨越亚纳光度的介观长度尺度。非技术性：通过西北大学原子 - 探针断层扫描中心（Nucapt）PIS PIS正在教育本科工作，高级论文，本科生的研究经验（REU）和教师（RET）的研究经验（RET），以使用LEAP Tomography进行Atom Probobsography。这些计划具有并将涉及男性，女人和合法的少数群体，西班牙裔和非裔美国人。 Nucapt还为其他大学，国家实验室和工业公司提供了适当的服务。此外，PI将在链接原子级实验和计算上开发一个夏季研讨会，？将在赠款第二年在西北部举行。本课程将针对对原子级和多尺度计算以及原子级实验以及年轻教职员工和工业参与者感兴趣的研究生。 PI正在计划CA。 50名参与者打算收取适度的注册费来支付费用。