Collaborative Research: Integrating Nanoparticle Self-assembly into Laser/Powder-based Additive Manufacturing of Multimodal Metallic Materials

Design of multimodal microstructures has emerged as a promising strategy for the discovery and development of metallic materials with a great strength-ductility combination for structural applications. Such a design strategy is of particular importance for elemental or single-phase metals. However, current manufacturing methodologies for multimodal material fabrications face a major technical challenge of controlling the three-dimensional microstructural heterogeneity. This collaborative research award supports fundamental research towards understanding the mechanisms of how nanoparticles assemble on their own in laser/powder-based additive manufacturing (AM) to alter grain nucleation and growth and achieve effective manufacturing of multimodal materials with desired microstructural heterogeneity. By including special nanoparticles in powder feedstock and plausibly achieving self-assembly of added nanoparticles in solidification fronts, this fabrication means, capable of influencing grain sizes and geometries if successful, will lead to a manufacturing technology for a large variety of multimodal metallic materials with improved properties towards critical applications in aerospace, automotive, military, and biomedical industries. This joint project will also provide a training platform for a diversified student body through research opportunities and will broaden participations from women and underrepresented students in research. The theme and results of this project will be utilized to enhance the engineering partnership with local community colleges around the region of the two institutions. The overall goal of this research is to gain fundamental understanding of the mechanisms that govern nanoparticle self-assembly behavior, microstructure evolution, and property enhancement in AM of multimodal titanium and its alloys using a laser heat source and powder feedstock. The effect of nanoparticle self-assembly at the liquid-crystal interface on solidification front stability and grain nucleation and growth during laser AM will first be investigated using three-dimensional phase-field simulation incorporating CALPHAD databases with experimental characterizations of grain changes. Next, using micromechanical modeling and crystal plasticity simulations, the team will elucidate the modified and improved strength-ductility combinations as affected by the three-dimensional distribution of multimodal grain structures. With the knowledge of grain modification and three-dimensional grain structure designs, metal AM experiments, using both powder-bed fusion (PBF) and directed energy deposition (DED), while integrating nanoparticle self-assembly, will be systematically designed and performed to investigate and establish the process-microstructure-property relationship. The new knowledge of nanoparticle self-assembly at the liquid-crystal interfaces during rapid solidification as in PBF and DED will be beneficial to other fusion-based manufacturing technologies, including welding, casting, and electron-beam manufacturing. Furthermore, basic knowledge of process-microstructure-property relationship in metal AM will lead to the development of novel multimodal materials with potentially unprecedented mechanical properties for widespread applications. This project is jointly funded by the Advanced Manufacturing program and the Established Program to Stimulate Competitive Research (EPSCoR). 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.