Collaborative Research: Pore Formation Mechanisms in Laser Powder-Bed Fusion Additive Manufacturing: Particle-Resolved Modeling and Fundamental Experimentation

合作研究：激光粉末床熔融增材制造中的孔隙形成机制：粒子分辨建模和基础实验

• 批准号: 1663364
• 负责人: Alexey Volkov
• 金额: $ 11.06万
• 依托单位: University of Alabama Tuscaloosa
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-06-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1663364&HistoricalAwards=false
• 关键词: Collaborative; Research; Pore; Formation; Mechanisms

Additive manufacturing (AM) has created a new paradigm of integrated materials, design and manufacturing innovations for effective product development and realization across a broad range of industries. Metal AM technologies such as selective laser melting (SLM), which uses a powder-bed and a high power laser, are especially beneficial in making complex-geometry, high-performance components without incurring tooling costs, giving early adopters a competitive advantage in the global market. One of the key challenges that hinder efficient metal AM technology implementation in industry is part quality inconsistency that is significantly affected by porosity in AM parts. Pores, with sizes of one to one hundred microns, are internal defects generated during the process and that cause large variations in part performance. Pore formation in metal AM is complex and not fully understood, making it difficult to predict for quality control. This award corroborates basic research needs of the porosity issue in metal AM parts. The project tackles original research on the coupled multi-scale and multi-physics process of heating, melting and solidification of numerous microscopic metallic particles in SLM. Research findings will not only establish correlations between the process parameters, material properties and pore attributes, but may also lead to novel techniques for mitigating pore defects, and thus, have a potential to accelerate metal AM adoption in U.S. industry. In addition, this project will contribute toward workforce training for metal AM industrial needs and attract high school students into advanced manufacturing technologies. The objectives of this research are to distinguish pore formation mechanisms in SLM and to theoretically predict, analyze and experimentally characterize the porosity in SLM parts. In this collaborative research between the University of Louisville (UofL) and the University of Alabama (UA), a hybrid numerical modeling technique will be developed for particle-resolved simulations capable of capturing different pore formation mechanisms in SLM. The model will be validated by SLM experiments of small-scale specimen fabrications, incorporating an infrared thermal imager for process temperature and melt-pool dynamics. The fabricated specimens will be measured using micro-scale x-ray computed-tomography and analyzed to attain statistical data of detailed porosity attributes for comparison with the results from numerical modeling. The research efforts will be extended to study the relationship between process parameters and morphology and distribution of porosity in SLM, and to estimate process windows that minimize pore defects. If successful, this study will distill knowledge of a convoluted multi-physics phenomenon and will offer significant insight detailing the key to particular mechanisms of different pore formations. The research results will be included in the training materials for the Additive Manufacturing Competency Center on the University of Louisville campus, providing practitioners of the SLM technology with better understanding of the relationship between processing parameters, porosity formation, and mechanical properties of critical AM-fabricated components.

增材制造（AM）创造了一种集成材料、设计和制造创新的新范式，用于在广泛的行业中进行有效的产品开发和实现。金属AM技术，如选择性激光熔化（SLM），使用粉末床和高功率激光，特别有利于制造复杂几何形状的高性能部件，而不会产生模具成本，使早期采用者在全球市场上具有竞争优势。阻碍金属增材制造技术在工业中有效实施的关键挑战之一是零件质量不一致，这受到增材制造零件中孔隙率的显著影响。孔径为1至100微米的孔隙是在加工过程中产生的内部缺陷，会导致部件性能的大幅变化。金属AM中的孔隙形成是复杂的并且尚未完全理解，使得难以预测质量控制。该奖项证实了金属AM部件中孔隙率问题的基本研究需求。该项目解决了SLM中众多微观金属颗粒的加热，熔化和凝固的耦合多尺度和多物理过程的原始研究。研究结果不仅将建立工艺参数，材料性能和孔隙属性之间的相关性，而且还可能导致减轻孔隙缺陷的新技术，从而有可能加速美国工业中金属AM的采用。此外，该项目还将为金属AM工业需求的劳动力培训做出贡献，并吸引高中生进入先进制造技术领域。本研究的目的是区分SLM中的孔隙形成机制，并从理论上预测，分析和实验表征SLM部件中的孔隙率。在路易斯维尔大学（UofL）和亚拉巴马大学（UA）之间的这项合作研究中，将开发一种混合数值模拟技术，用于能够捕获SLM中不同孔隙形成机制的粒子分辨模拟。该模型将被验证SLM实验的小规模的标本制作，将红外热成像仪的过程温度和熔池动态。将使用微尺度X射线计算机断层扫描测量和分析制造的试样，以获得详细的孔隙度属性的统计数据，用于与数值模拟的结果进行比较。研究工作将扩展到研究工艺参数与SLM中孔隙率的形态和分布之间的关系，并估计最小化孔隙缺陷的工艺窗口。如果成功的话，这项研究将提炼出复杂的多物理现象的知识，并将提供重要的见解，详细说明不同孔隙形成的特定机制。研究结果将被纳入路易斯维尔大学增材制造能力中心的培训材料中，为SLM技术的从业者提供更好地了解关键AM制造组件的工艺参数，孔隙率形成和机械性能之间的关系。