CAREER: Advancing Laser Powder Bed Fusion with Non-Spherical Powder

该学院早期职业发展(CALEAR)奖将支持旨在解决当前添加剂制造(AM)实践的局限性的研究，这些AM实践主要使用昂贵和能源密集型球形粉末材料。冷机械驱动方法使用往复刀具的磨粒研磨，实现了精确的粉末粒度分布，从而减少了能量输入，生产出了无气孔的金属粉末。该项目的目标是：(1)通过多模式粒子和混合粉末分配器增强粉末传播动力学，以及(2)改善激光与粉末的相互作用和微观结构控制。如果成功，项目成果可能会扩大材料选择，使各种AM工艺(如粘结剂喷射和激光/电子束粉床融合)的生产更具成本效益和可持续性。该项目为不同类型的本科生提供了研究机会，包括来自代表性不足群体和退伍军人的学生。通过实践研究经验、外展活动和创建视频动画，该项目将使未被充分代表的社区和高中生参与金属添加剂制造领域。该职业研究项目旨在解决三个基础研究问题：(1)非球形粉末特性，如形貌和尺寸，影响粉末-粉末相互作用，可能导致较低的堆积密度和不均匀的粉末床层。这将通过开发一种使用多模式粉末尺寸的沉积机制和一种创新的非接触式静电粉末撒布器来解决。(2)激光与粉末的相互作用受形状、形貌和尺寸分布等特性的影响。在较高的激光扫描速度下，由于非球形粉末的遮蔽效应，导致稳定/不稳定小孔模式的移动，将影响工艺图和颗粒的机械互锁。将利用同步加速器X射线成像和多物理模型等现场观测，对激光-粉末相互作用进行全面研究。这种方法旨在揭开潜在的物理和制定处理策略，以有效地解决预期的缺陷。(3)阴影效应导致的局部冷却速度降低影响了凝固过程、冲击组织和最终的力学性能。这将通过调整工艺参数和应用后热处理来解决，如热等静压，预计将实现等轴晶组织，以改善强度和塑性，可与变形合金媲美。研究成果有可能弥合基本理解和实际应用之间的差距，为添加剂制造创造一个可持续的未来。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This Faculty Early Career Development (CAREER) award will support research that intends to address the limitations of current additive manufacturing (AM) practices that primarily use expensive and energy-intensive spherical powdered materials. The cold mechanically driven method employs attrition milling with a reciprocating cutter, achieving precise powder size distribution, leading to the production of pore-free metal powders with reduced energy input. The project aims to: (1) enhance powder-spreading dynamics through multimodal particles and a hybrid powder dispenser, and (2) improve laser-powder interaction and microstructure control. If successful, the project outcomes may expand material choices, making production more cost-effective and sustainable across various AM processes such as binder jetting and laser/electron beam powder bed fusion. The project provides research opportunities to a diverse pool of undergraduate students, including those from underrepresented groups and veterans. Through hands-on research experiences, outreach activities, and the creation of video animations, the project will engage underrepresented communities and high school students in the field of metal additive manufacturing. The CAREER research project aims to address three fundamental research problems: (1) Non-spherical powder characteristics, such as morphology and size, impact powder-powder interactions, potentially leading to lower packing density and non-uniform powder beds. This will be addressed by developing a deposition mechanism using multimodal powder sizes and an innovative non-contact electrostatic powder spreader. (2) Laser-powder interaction is affected by characteristics such as shape, morphology, and size distribution. The shift in the stable/unstable keyhole mode due to the shadowing effect of non-spherical powder at higher laser scan speeds will influence the process map, and mechanical interlocking of particles. Comprehensive investigations into laser-powder interactions will be undertaken, using in-situ observations such as synchrotron X-ray imaging and multi-physics modeling. This approach aims to unravel the underlying physics and formulate processing strategies to effectively address anticipated defects. (3) Locally reduced cooling rates from the shadowing effect influence solidification, impacting microstructure and resultant mechanical properties. This will be addressed by adjusting process parameters and applying post-heat treatments, such as hot isostatic pressing, which is expected to achieve equiaxed grain structures for improved strength and ductility comparable to wrought alloys. The research outcomes have the potential to bridge the gap between fundamental understanding and practical applications, fostering a sustainable future for additive manufacturing.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.