Collaborative Research: Formation and Stability of Eutectic Nanostructures in Laser-Irradiated Particle Suspensions

合作研究：激光照射颗粒悬浮液中共晶纳米结构的形成和稳定性

• 批准号: 1663085
• 负责人: J. Floro
• 金额: $ 37.66万
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-10-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1663085&HistoricalAwards=false
• 关键词: Collaborative; Research; Formation; Stability; Eutectic

Powder metallurgy, in which complex parts are made by fusing together a metal powder, has a large economic footprint in the USA. This footprint will only grow as additive manufacturing (AM) techniques become more pervasive. A pressing concern with AM is that the parts produced often have worse mechanical properties than parts produced from forging or machining. The goal of this collaborative project is to develop new approaches to create a nanoscale physical structure within powder particles in order to improve mechanical properties (strength and thermal conductivity) of final parts. To accomplish this, this research will use lasers to melt different metal and ceramic alloys that have a special chemical composition, known as a eutectic, which produces an internal sheet-like structure. By lasing the powders while they are in a fluid that extracts heat quickly, the eutectic structure can be preserved when the particle solidifies. This work will suspend the powder particles in liquid and solid media that can remove heat, but these media must not react, boil, or obscure the laser. Experiments will be combined with modeling to understand the removal of heat, and to simulate how the internal structure forms within indivdual spherical particles under these conditions. Success in this research would enable a new class of tailored materials to be used in sintering and additive manufacturing to rapidly manufacture complex pieces with improved technical properties. This will have significant direct benefits for the aerospace, automotive, medical products, and defense industries. In addition, the PIs have a good history of recruiting underrepresented minority students in their research, and this effort will continue.Pulsed laser melting and cooling in certain fluids can provide very fast solidification rates to form nanoscale eutectic structures. Unfortunately, in materials with high optical absorption, lasers with nanosecond pulse widths only melt the near-surface region and cannot be considered true bulk processing techniques. This research will circumvent this limitation by using laser irradiation of eutectic alloys in powder form. Most investigations of eutectic solidification in discrete particles have used molten droplets formed by atomization, where heat extraction from the particle into a surrounding gas is inefficient. Although rapid eutectic solidification still occurs, atomization results in highly heterogeneous internal microstructures, which are undesirable with respect to many technical properties. This research will employ particles suspended in liquid or solid media that can extract heat much more efficiently following pulsed laser melting. The suspensions will be volume-restricted such that boiling of the media in contact with the molten particles is suppressed, thereby maintaining effective heat dissipation. In addition, by controlling the laser power and number of pulses, it is possible to partially melt a particle if desired. The experiments will examine these processes in metallic, semiconducting and metal-oxide alloy powders. The dynamic rapid solidification process in bulk and three-dimensional particles will be simulated in detail using the phase field modeling approach. The stability of the nanoscale eutectic structure during spark plasma sintering of the produced particulate material will also be examined.The Broader Impacts of this research include the new processing approaches that create tailored microstructures in feedstock materials for use in sintering and additive manufacturing that will yield improved mechanical and electrical properties in rapidly-manufactured components. This will have significant direct benefits for the aerospace, automotive, medical products, and defense industries.

粉末冶金，其中复杂的零件是由熔融在一起的金属粉末，在美国有很大的经济足迹。随着增材制造（AM）技术变得越来越普遍，这种足迹只会增加。AM的一个紧迫问题是，生产的零件往往比锻造或机加工生产的零件具有更差的机械性能。该合作项目的目标是开发新的方法，在粉末颗粒内创建纳米级物理结构，以提高最终部件的机械性能（强度和导热性）。为了实现这一目标，这项研究将使用激光熔化不同的金属和陶瓷合金，这些合金具有特殊的化学成分，称为共晶，产生内部片状结构。当粉末处于快速吸热的流体中时，通过激光照射粉末，当颗粒固化时，共晶结构可以被保留。这项工作将使粉末颗粒悬浮在可以散热的液体和固体介质中，但这些介质不得发生反应，沸腾或遮挡激光。实验将与建模相结合，以了解热量的去除，并模拟在这些条件下单个球形颗粒内部结构的形成。这项研究的成功将使一类新的定制材料能够用于烧结和增材制造，以快速制造具有改进技术性能的复杂零件。这将为航空航天、汽车、医疗产品和国防工业带来巨大的直接利益。此外，PI在招募少数民族学生参与其研究方面有着良好的历史，这一努力将继续下去。脉冲激光熔化和冷却在某些流体中可以提供非常快的凝固速率，形成纳米级共晶结构。不幸的是，在具有高光学吸收的材料中，具有纳秒脉冲宽度的激光仅熔化近表面区域，并且不能被认为是真正的体加工技术。本研究将通过使用粉末形式的共晶合金的激光辐照来规避这一限制。大多数离散颗粒中的共晶凝固的研究使用通过雾化形成的熔融液滴，其中从颗粒到周围气体中的热提取是低效的。虽然快速共晶凝固仍然发生，雾化导致高度不均匀的内部微观结构，这是不可取的，就许多技术性能。这项研究将采用悬浮在液体或固体介质中的颗粒，这些颗粒可以在脉冲激光熔化后更有效地提取热量。悬浮液将是体积受限的，使得与熔融颗粒接触的介质的沸腾被抑制，从而保持有效的散热。此外，通过控制激光功率和脉冲数，如果需要，可以部分熔化颗粒。实验将研究这些过程中的金属，半导体和金属氧化物合金粉末。采用相场模拟方法，详细模拟了块状和三维颗粒的动态快速凝固过程。该研究的更广泛的影响包括新的加工方法，在烧结和增材制造中使用的原料材料中创建定制的微观结构，这将在快速制造的部件中产生更好的机械和电气性能。这将为航空航天、汽车、医疗产品和国防工业带来巨大的直接利益。

项目成果

Lamellar instabilities during scanning laser melting of Al–Cu eutectic and hypoeutectic thin films

Al-Cu共晶和亚共晶薄膜扫描激光熔化过程中的层状不稳定性

• DOI: 10.1016/j.jallcom.2021.158800
• 发表时间: 2021
• 期刊: Journal of Alloys and Compounds
• 影响因子: 6.2
• 作者: Sullivan, E.J.;Tomko, J.A.;Skelton, J.M.;Fitz-Gerald, J.M.;Hopkins, P.E.;Floro, J.A.
• 通讯作者: Floro, J.A.

Efficacy of elemental mixing of in situ alloyed Al-33wt%Cu during laser powder bed fusion

• DOI: 10.1016/j.jmatprotec.2021.117379
• 发表时间: 2022-01
• 期刊: Journal of Materials Processing Technology
• 影响因子: 6.3
• 作者: J. Skelton;E. Sullivan;J. Fitz-Gerald;J. Floro

On the Morphology Changes of Al and Al-Cu Powder After Laser Melting

• DOI: 10.1007/s11663-020-01902-z
• 发表时间: 2020-07
• 期刊: Metallurgical and Materials Transactions B
• 作者: J. Skelton;C. V. Headley;E. Sullivan;J. Fitz-Gerald;J. Floro