NSF-BSF:Influence of cohesion enhancing elements, impurities and hydrogen/deuterium at grain boundaries and heterophase interfaces on embrittlement of additive-manufactured steels

非技术总结：在制造、储存或服务过程中，钢暴露于氢（1H）可能会使其变脆，可能导致灾难性故障。因此，钢的氢脆（HE）在1H能源系统、汽车、航空、海洋应用、桥梁、交通基础设施和核反应堆中受到关注。原子ppm范围内的1H浓度足以使高强度钢脆化。1H在缺陷、晶界、异相界面和弹性应力场处的捕获影响其溶解度、扩散率和钢对HE的敏感性。增材制造（AM）钢可能比其对应的锻钢更容易受到HE的影响，这是由于不同的微观结构、孔隙率水平和残余应力水平。了解氢进入、局部浓度、捕获与移动的氢及其三维空间分布，对于下一代耐氢钢的化学和微观结构设计非常重要。PI提出了一项系统的研究，首先是设计一种新型的沉淀硬化不锈钢，用于选择性激光熔化;控制粉末合成和表征;通过粉末床熔融SLM和定向能量沉积激光工程净成形对钢进行AM; AM钢与其锻造对应钢相比的化学、显微组织和机械特性，在1H或2D电化学充电之前和之后。科学技术战略和合金设计原则将直接支持工业制造AM的发展。科学技术战略和合金设计原则将支持AM工业制造的发展。我们的项目将为学生和博士后提供多维培训，包括加工-结构-性能关系、材料科学工程的基本范式&、物理冶金和合金设计、高级原子级结构/化学表征、第一性原理计算、HE、力学性能评估和失效分析。技术总结：拟议研究的首要科学主题是了解不同元素，杂质和1H或2D的影响，对AM材料中与HE有关的晶界和异相界面的结合能进行了研究，重点是从经典的17-4 PH钢衍生的PH不锈钢。包括锻造17-4PH钢以提供用于与AM处理的钢进行比较的参考基础，即，QT17-4+。这将使我们能够更好地理解合金元素、杂质和1H或2D的晶粒和异相边界偏析的影响，以及不同加工条件（例如，加热速率）对微观结构（马氏体板条和原奥氏体晶界的GB特性）、GB内聚力和对HE的敏感性的影响。从这个详细的了解，我们将制定缓解战略的脆化AM和/或焊接组件，并使用合金设计原则，以优化界面的凝聚力的缺陷，关键的HE。生成的基础数据将为下一代钢铁设计铺平道路，并支持AM发展所带来的工业革命。PI将开发一个在线研究生课程，金属材料的增材制造：理论与实践，用于特拉维夫大学和西北大学的教学。学生将组成四人一组，并将所学的主题应用于快速制造设计项目。学生将获得写作和向技术观众展示的重要经验。在NUCAPT，PI将继续通过NSF资助的材料研究科学与工程中心的NSF-REU项目，SHYNE资源，针对妇女和代表性不足的少数民族，勤工俭学和高级项目学生，国立大学，国家实验室，该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准。

Non-Technical Summary:Exposure of steels to hydrogen (1H) during manufacturing, storage or service may embrittle them, potentially resulting in catastrophic failures. Therefore, hydrogen embrittlement (HE) of steels is of concern in 1H energy systems, automobiles, aviation, marine applications, bridges, transportation infrastructure, and nuclear reactors. 1H concentrations in the atomic ppm range are sufficient to embrittle high-strength steels. 1H trapping at defects, grain boundaries, heterophase interfaces, and elastic stress-fields, affects its solubility, diffusivity, and the susceptibility of steels to HE. Additively manufactured (AM) steels may be more susceptible to HE than their counterpart wrought steels due to different microstructures, porosity levels, and residual stress levels. The understanding of 1H ingress, local concentrations, trapping vs. mobile 1H, and its 3D spatial distributions, is important for chemical and microstructural design of next-generation, hydrogen-resistant steels. The PIs are proposing a systematic study starting with the design of a novel precipitation-hardened stainless steel for selective laser melting; controlled powder synthesis and characterization; AM of steels by both powder-bed fusion SLM and directed energy deposition laser engineered net shaping; chemical, microstructural, and mechanical characterization of AM steels compared to their wrought counterpart steel, before and after 1H or 2D electrochemical charging. Scientific and technological strategies and alloy design principles will directly support the development of AM for industrial manufacturing. The scientific and technological strategies and alloy design principles will support the development of AM for industrial manufacturing. Our projects will provide multi-dimensional training for students and postdocs, including processing-structure-properties relationships, the fundamental paradigm of materials science & engineering, physical metallurgy and alloy design, advanced atomic-level structural/chemical characterization, first-principles calculations, HE, mechanical properties evaluation and failure analysis.Technical Summary:The overarching scientific theme of the proposed research is to understand the effects of different elements, impurities and either 1H or 2D, on the cohesive energies of GBs and heterophase interfaces concerning HE in AM materials, focusing on PH stainless steels derived from the classical 17-4 PH steel. Wrought 17-4PH steel is included to provide a reference basis for comparison with the AM processed steels, i.e., QT17-4+. This will enable us to better understand the influence of grain- and heterophase-boundary segregation of alloying elements, impurities, and 1H or 2D, and the effects of different processing conditions (e.g., heating rates) on the microstructures (GB characteristics of martensite lath and prior austenite grain-boundaries), GB cohesion, and susceptibility to HE. From this detailed understanding, we will develop mitigation strategies for embrittlement of AM and/or welded components and use alloy design principles to optimize interfacial cohesion of the defects critical for HE. The fundamental data generated will pave the way to next-generation steel designs and support the industrial revolution created by the development of AM. The PIs will develop an online graduate-level course, Additive Manufacturing of Metallic Materials: Theory and Practice, for teaching at Tel Aviv University and Northwestern. Students will form groups of four and apply topics learned to a rapid manufacturing design project. Students will gain significant experience with writing and presenting to a technical audience. At NUCAPT, the PIs will continue undergraduate student projects through the NSF-REU programs of the NSF-funded Materials Research Science and Engineering Center, SHyNE resource, programs aimed at women and underrepresented minorities, work-study and senior project students, national universities, national laboratories, and industry.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.