Laser Additive Manufacturing of Metal Matrix Nanocomposites

激光添加制造是3D打印家族中的一种分层沉积工艺，对于直接生产复杂的金属零件具有重要意义。近年来，纳米颗粒增强金属材料(即金属基纳米复合材料)在显著提高力学性能方面显示出巨大的潜力。因此，激光添加法制备金属基纳米复合材料具有广阔的应用前景。然而，在金属零件的激光添加制造中，一些长期存在的挑战限制了机械性能和形状精度。该奖项支持基础研究，以提供打破现有障碍所需的知识，扩大航空航天、国防、汽车和生物医药行业的工艺能力和应用空间，从而增强美国在全球先进制造业的竞争力。将通过课程开发和改进来加强对本科生和研究生的工程教育。该项目还将吸引更多历史上代表性不足的学生。该项目的研究目标是了解(1)不同类型、载荷、大小和形状的纳米粒子对微观结构、材料性能、表面光洁度/精度和残余应力的累积影响；(2)在金属基纳米复合材料的激光添加制造中，纳米粒子对熔池和熔覆层的激光吸收和热物理性能的影响。单层和多层(3~5层)金属基纳米复合材料与不同类型、不同载量、不同尺寸和形状的纳米颗粒将被激光沉积。光学和电子显微镜、白光干涉仪、X射线衍射和微/纳米机械测试将分别用于测量微结构、表面光洁度/精度、残余应力和材料性能。添加剂制造过程中的激光吸收将通过光功率传感器测量；激光诱导熔池和沉积纳米复合材料的热物理性质将通过实验确定，包括比热(通过差示扫描量热法)、导热系数(通过激光闪光法)、熔池粘度(通过高温粘度计)和熔池表面张力(通过座滴实验)。

Laser additive manufacturing, a layered deposition process in the family of 3D Printing, is of significance to directly produce complex metallic parts. Nanoparticle reinforced metallic materials (i.e. metal matrix nanocomposites) have recently demonstrated great potentials to achieve significantly enhanced mechanical properties. Laser additive manufacturing of metal matrix nanocomposites will thus be promising for widespread applications. However, there are some long-standing challenges limiting the mechanical performance and shape accuracy in laser additive manufacturing of metal parts. This award support fundamental research to provide knowledge needed to break the existing barriers and extend the process capability and application space in aerospace, defense, automotive, and biomedical industries, thus enhancing US competiveness in global advanced manufacturing. Engineering education for both undergraduate and graduate students will be enhanced through curriculum developments and improvements. The project will also attract more historically underrepresented students. K-12 students, teachers, and industries will be exposed to the new technology.The research objective of this project is to understand (1) the accumulative effects of nanoparticles (of various types, loadings, sizes, and shapes) on microstructure, material properties, surface finish/accuracy, and residual stress; and (2) the effects of nanoparticles on laser absorption and thermophysical properties of molten pool and deposited layers in laser additive manufacturing of metal matrix nanocomposites. Single and multiple layers (3~5 layers) of metal matrix nanocomposites with nanoparticles (of various types, loadings, sizes, and shapes) will be laser deposited. Optical and electron microscopies, white light interferometer, X-ray diffraction, and micro/nano-mechanical testing will be used to measure microstructure, surface finish/accuracy, residue stress, and material properties, respectively. Laser absorption during additive manufacturing will be measured by optical power sensor; thermophysical properties of laser-induced molten pool and deposited nanocomposites will be determined experimentally, including specific heat (by differential scanning calorimetry), thermal conductivity (by laser flash method), viscosity of molten pool (by high temperature viscometer), and surface tension of molten pool (by sessile drop experiments).