Pore Formation and Polymer Thermal Debinding during Vapor-Induced Phase Separation-Enabled Metal Printing

金属增材制造对于从汽车零件到喷气发动机到医疗植入物的复杂金属部件的制造具有极大的兴趣。尽管其优于传统的金属制造方法，但目前的金属增材制造技术面临着挑战，包括处理可能爆炸的金属粉末，以及用异质材料制造零件以增强零件性能。本项目旨在探索一种室温聚合物粘合剂辅助金属印刷技术，该技术使用由金属粉末和溶解的聚合物制成的悬浮油墨。新工艺有两个优点：（1）使用金属-聚合物悬浮油墨减少了机器操作员处理和吸入金属粉末的危险;（2）通过调整悬浮油墨的金属成分，可以沉积异质材料。同时，该项目将促进以科学为基础的制造业教育，以扩大在STEM中代表性不足和少数民族学生的参与，并为快速发展的制造业培养制造业劳动力。在各种金属打印技术中，粉末床融合（PBF）和定向能量沉积（DED）是最常见的模式。PBF和DED是能量驱动的高温打印工艺，需要在打印前后处理金属粉末。结合粉末挤出的进步允许使用以细丝形式预结合的金属粉末，然而，这限制了材料的选择。气相诱导相分离三维打印技术（VIPS-3DP）利用金属-聚合物悬浮液作为构建材料，VIPS作为固化机制。将所得金属-聚合物绿色部件进一步加工用于聚合物热脱脂和烧结以获得最终金属部件。本研究的目的是研究在印刷过程中的金属-聚合物绿色部件中的互连孔隙空间的形成的聚合物粘合剂的VIPS诱导的固化的效果和由此产生的互连孔隙对聚合物热脱脂过程中的裂纹发生的影响。该研究将通过两个任务来实现：（1）多孔微观结构演变和热脱脂过程的理论建模，以及（2）印刷绿色，棕色和最终部件的微观结构和机械性能的实验表征。 该奖项反映了NSF的法定使命，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。

Metal additive manufacturing has been of great interest for the fabrication of complex metallic components ranging from automobile parts to jet engines to medical implants. Despite its advantages over conventional metal fabrication methods, current metal additive manufacturing technologies are subject to challenges including handling metal powders, which can be explosive, and fabricating parts with heterogeneous materials to enhance part properties. This project aims to explore a room-temperature polymer binder-assisted metal printing technology, which uses suspension inks made of metallic powders and dissolved polymer. The new process has two advantages: (1) using metal-polymer suspension inks reduces the hazards of handling and inhaling metallic powders for machine operators; and (2) heterogeneous materials can be deposited by adjusting the metal composition of suspension inks. Simultaneously this project will stimulate science-based manufacturing education to broaden the participation of underrepresented and minority students in STEM and prepare a manufacturing workforce for the fast-evolving manufacturing industry.Of various metal printing technologies, powder bed fusion (PBF) and directed energy deposition (DED) are the most common modalities. PBF and DED are energy-driven high-temperature printing processes and require handling metal powders before and after printing. Advances in bound powder extrusion allow the use of metal powders pre-bound in the form of a filament, which, however, limits the choices of materials. The vapor-induced phase separation-enabled three-dimensional printing technology (VIPS-3DP) utilizes metal-polymer suspensions as build materials and VIPS as the solidification mechanism. The resultant metal-polymer green parts are further processed for polymer thermal debinding and sintering to get final metallic parts. The objective of this research is to study the effect of the VIPS-induced solidification of polymer binder on the formation of an interconnected pore space in metal-polymer green parts during printing and the effect of the resulting interconnected pores on the crack occurrence during polymer thermal debinding. The research will be implemented via two tasks: (1) theoretical modeling of the porous microstructure evolution and thermal debinding processes, and (2) experimental characterization of printed green, brown, and final parts in terms of their microstructure and mechanical properties. The resulting knowledge of the VIPS-induced porous microstructure and its effect on thermal debinding may lead to new sustainable metal additive manufacturing technologies.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.