Collaborative Research: Integrating Nanoparticle Self-assembly into Laser/Powder-based Additive Manufacturing of Multimodal Metallic Materials

多模态微结构设计已成为一种很有前途的策略，用于发现和开发具有良好强度-延性组合的金属材料。这种设计策略对元素或单相金属特别重要。然而，当前的多模态材料制造方法面临着控制三维微观结构非均质性的主要技术挑战。该合作研究奖支持对纳米颗粒如何在激光/粉末增材制造（AM）中自行组装机制的基础研究，以改变晶粒成核和生长，并实现具有所需微观结构非均质性的多模态材料的有效制造。通过在粉末原料中加入特殊的纳米颗粒，并在凝固前沿实现添加的纳米颗粒的自组装，这种制造方法如果成功的话，能够影响晶粒尺寸和几何形状，将导致一种制造技术，用于各种多模态金属材料，这些材料具有改进的性能，可用于航空航天、汽车、军事和生物医学行业的关键应用。这一联合项目还将通过研究机会为多样化的学生群体提供培训平台，并将扩大妇女和代表性不足的学生对研究的参与。该项目的主题和成果将用于加强与两所大学所在地区的当地社区大学的工程伙伴关系。本研究的总体目标是通过激光热源和粉末原料对多模态钛及其合金增材制造中纳米颗粒自组装行为、微观结构演变和性能增强的机制进行基本理解。在激光增材制造过程中，纳米颗粒在液晶界面的自组装对凝固前沿稳定性和晶粒形核和生长的影响将首先通过三维相场模拟研究，结合calphhad数据库和晶粒变化的实验表征。接下来，利用微观力学建模和晶体塑性模拟，该团队将阐明受多模态晶粒结构三维分布影响的改进和改进的强度-塑性组合。在晶粒改性和三维晶粒结构设计的基础上，我们将系统地设计和进行金属增材制造实验，利用粉末床熔合（PBF）和定向能沉积（DED），同时集成纳米粒子自组装，以研究和建立工艺-微观结构-性能之间的关系。在PBF和DED等快速凝固过程中，纳米粒子在液晶界面自组装的新知识将有利于其他基于熔合的制造技术，包括焊接、铸造和电子束制造。此外，金属增材制造中工艺-微观结构-性能关系的基本知识将导致具有潜在前所未有的机械性能的新型多模态材料的发展，从而广泛应用。该项目由先进制造计划和促进竞争研究的既定计划（EPSCoR）共同资助。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。

Design of multimodal microstructures has emerged as a promising strategy for the discovery and development of metallic materials with a great strength-ductility combination for structural applications. Such a design strategy is of particular importance for elemental or single-phase metals. However, current manufacturing methodologies for multimodal material fabrications face a major technical challenge of controlling the three-dimensional microstructural heterogeneity. This collaborative research award supports fundamental research towards understanding the mechanisms of how nanoparticles assemble on their own in laser/powder-based additive manufacturing (AM) to alter grain nucleation and growth and achieve effective manufacturing of multimodal materials with desired microstructural heterogeneity. By including special nanoparticles in powder feedstock and plausibly achieving self-assembly of added nanoparticles in solidification fronts, this fabrication means, capable of influencing grain sizes and geometries if successful, will lead to a manufacturing technology for a large variety of multimodal metallic materials with improved properties towards critical applications in aerospace, automotive, military, and biomedical industries. This joint project will also provide a training platform for a diversified student body through research opportunities and will broaden participations from women and underrepresented students in research. The theme and results of this project will be utilized to enhance the engineering partnership with local community colleges around the region of the two institutions.The overall goal of this research is to gain fundamental understanding of the mechanisms that govern nanoparticle self-assembly behavior, microstructure evolution, and property enhancement in AM of multimodal titanium and its alloys using a laser heat source and powder feedstock. The effect of nanoparticle self-assembly at the liquid-crystal interface on solidification front stability and grain nucleation and growth during laser AM will first be investigated using three-dimensional phase-field simulation incorporating CALPHAD databases with experimental characterizations of grain changes. Next, using micromechanical modeling and crystal plasticity simulations, the team will elucidate the modified and improved strength-ductility combinations as affected by the three-dimensional distribution of multimodal grain structures. With the knowledge of grain modification and three-dimensional grain structure designs, metal AM experiments, using both powder-bed fusion (PBF) and directed energy deposition (DED), while integrating nanoparticle self-assembly, will be systematically designed and performed to investigate and establish the process-microstructure-property relationship. The new knowledge of nanoparticle self-assembly at the liquid-crystal interfaces during rapid solidification as in PBF and DED will be beneficial to other fusion-based manufacturing technologies, including welding, casting, and electron-beam manufacturing. Furthermore, basic knowledge of process-microstructure-property relationship in metal AM will lead to the development of novel multimodal materials with potentially unprecedented mechanical properties for widespread applications. This project is jointly funded by the Advanced Manufacturing program and the Established Program to Stimulate Competitive Research (EPSCoR).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.