Ink-based additive manufacturing of high-entropy alloys from oxide and hydride powders

非技术摘要金属的添加制造(3D打印)正在为民用和国防应用的美国制造业带来革命性的变化，因为它允许在一次操作中创建复杂形状的物体，通常是通过使用激光熔化金属粉末。受聚合物3D打印的启发，这项工作专注于一种新颖的3D打印方法-3D墨水挤压-以创建坚固而轻便的金属对象。含有金属氢化物(氢化物)前驱体粉末和粘结剂的液体油墨被逐层挤压成固体细丝，然后加热以除去溶剂、粘结剂和氢，留下金属粉末的骨架。这种骨架在高温下加热，使金属粉末致密化，形成坚固而轻质的金属结构。与更成熟的制造方法相比，这种有希望的方法具有许多关键优势，包括成本更低、由于在空气中进行室温打印而提高了能效，以及形成更坚固的金属部件。该项目的总体目标是确定和预测这一前景看好的先进制造方法的关键参数。此外，一款基于网络的免费视频游戏PRIMA(金属和合金墨水打印机器人)正在为6-12年级的孩子们开发，该游戏向青少年(6-12年级)传达3D打印技术的设计和科学原理，以刺激、教育和激励他们从事STEM和制造业教育和职业。技术摘要本研究探索与一种新的添加剂制造方法-金属墨水挤压打印相关的基本物理现象。在这种方法中，含有混合(Co，Cr，Fe，Ni)氧化物颗粒或混合(Hf，Nb，Ta，Ti，Zr)氢化物颗粒的油墨被挤压印刷成细丝(单独或组装成微晶格)，然后还原/分解成金属，相互扩散形成高熵合金(HEA)，并进行烧结。系统地研究了共还原(对于氧化物)或共分解(对于氢化物)、金属互扩散和孔洞演化作为颗粒组成、大小和堆积分数的函数、还原物种(H2或C)以获得力学见解。同时，利用非原位金相技术和原位同步辐射X射线衍射法和层析成像技术研究了纤维、支柱和微桁架在挤压、均质和烧结过程中的气孔(部分烧结残留或通过发泡/保持器添加)的演变。这些实验数据允许开发基于扩散的模型和有限元模型，以便根据合成的微晶格、支柱孔隙率、相和几何形状预测和优化这一新的制造方法的特定机械性能。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。

Non-technical AbstractAdditive manufacturing (3D printing) of metals is revolutionizing US manufacturing for civilian and defense applications, as it allows the creation of complex-shaped objects in a single operation, typically by melting metal powders with a laser. Inspired by polymer 3D printing, this work focuses on a novel 3D printing method - 3D ink-extrusion - to create strong and lightweight metallic objects. A liquid ink containing metal-hydrogen (hydride) precursor powders and a binder is extruded into solid filaments, layer by layer, which is then heated to remove the solvent, binder and hydrogen, leaving behind a skeleton of metal powders. This skeleton is heated at a high temperature to densify the metal powders to form a strong and lightweight metallic structure. This promising approach has many key advantages as compared to the more established manufacturing methods, including lower costs, improved energy efficiency due to room-temperature printing in air, and formation of more robust metal components. The overall goal of this project is to identify and predict the critical parameters of this promising advanced manufacturing method. Furthermore, a web-based free-access video game, PRIMA (Printing Robots with Inks of Metals and Alloys), is being developed for youngsters (grades 6-12) that conveys the design and scientific principles of 3D-printing techniques in order to excite, educate, and motivate them to pursue STEM and manufacturing education and careers.Technical AbstractThis study explores the fundamental physical phenomena associated with a novel additive manufacturing approach, metallic ink-extrusion printing. In this method, inks containing mixed (Co,Cr,Fe,Ni) oxide particles or mixed (Hf,Nb,Ta,Ti,Zr) hydride particles are extrusion-printed into filaments (stand alone or assembled into micro-lattices), which are then reduced/decomposed to metals, inter-diffused to form high-entropy alloys (HEA), and sintered. Systematic studies of the co-reduction (for oxides) or co-decomposition (for hydrides), metal inter-diffusion and porosity evolution are performed as a function of particle composition, size and packing fraction, reducing species (H2 or C) for mechanistic insights. Also, the evolution of pores (remaining from partial sintering or added via foaming/space-holders) during the extrusion, homogenization and sintering of fibers, struts and micro-trusses are examined by both ex situ metallographic techniques and in situ synchrotron x-ray diffraction and tomography. These experimental data allow for the development of diffusion-based models and finite-element models in order to predict and optimize this novel manufacturing approach for specific mechanical properties based on the synthesized micro-lattices, strut porosity, phases, and geometry.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.