CAREER: Identifying the Micromechanisms Leading to Hydrogen-Induced Intergranular Fracture in Metals

职业：确定导致金属中氢致晶间断裂的微观机制

• 批准号: 1454072
• 负责人: Jaafar El-Awady
• 金额: $ 50万
• 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: 2015
• 资助国家: 美国
• 起止时间: 2015-02-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1454072&HistoricalAwards=false
• 关键词: CAREER; Identifying; Micromechanisms; Leading; Hydrogen

This Faculty Early Career Development (CAREER) Program project will identify the underlying deformation and failure mechanisms of nickel (Ni) and its alloys under coupled environmental and mechanical conditions. Nickel and nickel-based alloys are commonly used in many crucial service applications due to their high strength and fracture toughness. In many cases these materials are used in energy generating, conversion or storage systems. In such conditions a loss of toughness associated with exposure to hydrogen can occur. This award supports fundamental research on the effect of hydrogen on the deformation and fracture of metals, and will contribute to engineering practice via advances in the structural integrity of energy systems. The education and outreach tasks through this grant will contribute to efforts aiming to improve STEM achievement in Baltimore elementary public schools with a high minority student population. Practical engineering problems and solutions will be presented and discussed in the classroom with the goal to stimulate interest in engineering. Undergraduates from a local historically black college will obtain research internships allowing for active involvement in this CAREER research project. This will allow students to develop interest and foundations for careers in mechanics of materials. The primary research objectives of this CAREER project are to fundamentally identify the influence of H-diffusion on dislocation microstructure evolution, damage accumulation, and subsequent H-induced intergranular fracture of Ni crystals. We hypothesize that, unlike conventionally presumed, dislocation plasticity plays a major role in controlling material response and subsequent failure even in high-pressure H environments. We will perform unprecedented large scale 3D discrete dislocation dynamics (DDD) simulations coupled with finite element method to study dislocation evolution in H-charged single, bi, and poly-crystals. Details of the dislocation-H interactions, dislocation grain boundary interactions, and H pipe/bulk diffusion will be identified through molecular dynamics (MD) simulations, then hierarchically informed into DDD. In particular, this work will address two fundamental questions: (1) How does H influence dislocation multiplication/evolution? and (2) What is the role of H-diffusion on the evolution of the dislocation microstructure? The MD simulations will: (1) quantify H effects on the activation parameters of cross-slip; and (2) quantify H-diffusion coefficients and dislocation grain boundary interactions. Coupled H-diffusion/DDD simulations will be used to identify effects of H concentration and grain size on: (1) flow strength, and slip-morphology; and (2) dislocation evolution ahead of H-induced intergranular cracks. Simulations will be validated by comparisons with key experimental results from literature.

该学院早期职业发展(CALEAR)计划项目将确定镍(Ni)及其合金在耦合环境和机械条件下的潜在变形和失效机制。镍和镍基合金由于其高强度和断裂韧性，在许多重要的服务应用中被广泛使用。在许多情况下，这些材料用于发电、转换或储存系统。在这种情况下，可能会出现与接触氢有关的韧性损失。该奖项支持氢对金属变形和断裂的影响的基础研究，并将通过在能源系统结构完整性方面的进展为工程实践做出贡献。通过这笔赠款执行的教育和外展任务将有助于努力提高巴尔的摩少数民族学生人数较多的公立小学的STEM成绩。课堂上将介绍和讨论实际的工程问题和解决方案，目的是激发人们对工程的兴趣。来自当地一所历史悠久的黑人学院的本科生将获得研究实习机会，以便积极参与这一职业研究项目。这将使学生培养对材料力学职业的兴趣和基础。这一职业计划的主要研究目标是从根本上确定氢扩散对镍晶体位错微结构演化、损伤积累和随后的氢诱导沿晶断裂的影响。我们假设，与传统的假设不同，位错塑性在控制材料响应和随后的破坏方面发挥着主要作用，即使在高压H环境中也是如此。我们将进行史无前例的大规模三维离散位错动力学(DDD)模拟并结合有限元方法来研究带氢单晶、双晶和多晶中的位错演化。位错-H相互作用、位错晶界相互作用和H管/体扩散的细节将通过分子动力学(MD)模拟确定，然后分级通知到DDD。特别是，这项工作将解决两个基本问题：(1)H如何影响位错的增殖/演化？(2)氢扩散对位错微结构演化的作用是什么？分子动力学模拟将：(1)量化H对交叉滑移激活参数的影响；(2)量化H扩散系数和位错晶界相互作用。H-扩散/DDD耦合模拟将被用来确定H浓度和晶粒度对：(1)流动强度和滑移形态的影响；以及(2)H诱导晶间裂纹之前的位错演化。模拟将通过与文献中的关键实验结果的比较来验证。