CAREER: Advanced Surface Coating of Metallic Powders by Vibration-Enhanced High-Power Impulse Magnetron Sputtering for Sintering-Based Manufacturing

烧结是利用粉末原料生产密度可控材料的最实用的制造工艺之一。然而，生产工业应用的粉末合金前驱体是具有挑战性的。尽管通过传统的烧结方法，预混纯金属粉末的成分范围很广，但现代烧结技术的快速加热和快速冷却不可避免地会导致新的但不必要的化学梯度，以及组织和性能的各向异性。该学院早期职业发展奖将研究高功率脉冲磁控溅射工艺，作为一种先进的金属粉末表面改性技术。在形成核/壳体系的粉末上沉积薄膜可以使不同的合金在用作粉末原料时组织更加均匀和可控。这种新型粉末将为航空航天、汽车、能源和医疗保健行业的可再生部件的成本效益烧结提供可靠的原材料供应。该项目的综合教育和外展活动将主要集中在：1)教育和培训妇女和代表不足的少数族裔，作为先进制造业的下一代高技能领导者；2)建立一个多样化的本科生渠道，与弗吉尼亚州的詹姆斯·麦迪逊大学合作，通过特别的暑期项目进行研究生学习；以及3)实施一套在线虚拟实验室，研究核心/外壳结构的先进材料表征以及材料加工。该项目的总体研究目标是为将微米和纳米粉末表面改性为促进烧结基过程中三相转变的核/壳系统奠定科学基础。各种组合的核心/外壳(例如，铝-铜、钛-铜、铜-铬和镍-铬等)将是用于建模的共晶成分，因为它们与工业相关，形成沉淀硬化合金的能力，以及优异的高温性能。假设高功率脉冲磁控溅射结合持粉器的振动运动可以在粉末上获得共形薄膜，这是产生良好微结构的必要条件。为了验证这一假设，该项目将研究溅射放电，以了解包括振动在内的复杂几何形状(如球形粉末)上薄膜的成核和生长机制。本研究还旨在了解粉末-薄膜界面在核/壳两相扩散偶中的作用及其对烧结最终零件组织的影响。该项目的综合战略将带来一种制造适用于现代烧结工艺的核/壳材料的新方法。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。

Sintering is one of the most practical manufacturing processes in producing density-controlled materials from powder feedstock. However, producing industrially applicable powder alloy precursors is challenging. Although pre-mixing pure metal powders have allowed a wide range of compositions by conventional sintering, rapid heating and cooling in modern sintering techniques inevitably results in new but unwanted chemical gradients, as well as microstructural and property anisotropy. This Faculty Early Career Development (CAREER) award will investigate a high-power impulse magnetron sputtering process as an advanced technology to modify the surface of metallic powders. The deposition of thin films on the powders forming core/shell systems can provide solutions to make different alloys with more homogeneous and controlled microstructures when used as powder feedstock. This new class of powders will enable a reliable supply of raw materials for cost-effective sintering of reproducible components in the aerospace, automotive, energy, and healthcare industries. The integrated educational and outreach activities of this project will broadly concentrate on: 1) educating and training women and underrepresented minorities as the future generation of highly-skilled leaders in advanced manufacturing, 2) establishing a pipeline of diverse undergraduate students to pursue graduate studies in collaboration with James Madison University in Virginia through special summer programs, and 3) implementing an online set of virtual laboratories in advanced materials characterization of core/shell structures as well as materials processing. The overall research objective of this project is to establish the scientific underpinnings for the surface modification of micro- and nano-powders into core/shell systems that promote three-phase transformations in sintering-based processes. The core/shell of various combinations (e.g., aluminum-copper, titanium-copper, copper-chromium and nickel-chromium, etc.) will be the eutectic compositions for modeling because of their industrial relevance, an ability to form precipitation hardening alloys, and excellent high-temperature properties. It is hypothesized that high-power impulse magnetron sputtering combined with the vibrational motions of powder holders can achieve conformal thin films on powders, which are desired to produce favorable microstructures. To test the hypothesis, the project will study sputtering discharges to understand the nucleation and growth mechanism of thin films on complex geometries such as spherical powders when including vibrations. This research also aims to understand the role of powder-film interface in the two-phase core/shell diffusion couple and its effect on the final part microstructure from sintering. The combined strategy of the project will lead to a new method of manufacturing core/shell materials suitable for modern sintering processes.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.