Fundamental Understanding of Amorphization Mechanism and Intermetallic Prevention in Friction-based Solid-state Additive Manufacturing of Aluminum-steel Bimetallic Components

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Additive manufacturing of dissimilar alloys through depositing specific materials on a given substrate has the potential to achieve effective lightweight structures with required performance and functionality. Aluminum-steel bimetallic components are of strong interest in engineering structural applications because of their availability and affordability. However, direct bonding between aluminum alloys and steels using currently existing manufacturing methods often leads to detrimental intermetallic compounds at the interface, significantly degrading the bonding strength. This award will tackle fundamental research of a novel friction-based solid-state additive manufacturing process, during which localized shear deformation, due to high strain-rates, at dissimilar metallic interfaces may amorphize the processed alloys and suppress intermetallic formation. However, how atomic level diffusion at the bimetallic interface interacts with localized deformations and inhibits the formation of intermetallic compound is a critical knowledge gap hindering full comprehension of such a complex physical phenomenon. Thorough understanding from this research will not only reveal key knowledge necessary to advance dissimilar alloys joining by solid-state additive manufacturing, but also enable a rapid transition for realization and commercialization of high-performance aluminum-steel bimetallic component manufacture. Throughout the project, research materials will be incorporated into several undergraduate and graduate level courses in advanced manufacturing to prepare next-generation engineers for future manufacturing challenges.The specific research objectives of this project include: (1) elucidating the amorphization mechanism and intermetallic formation in high strain-rate solid-state additive manufacturing, which govern the bonding integrity at the joined aluminum-steel interface, (2) investigating the roles of key process parameters in determining aluminum-steel interfacial bond strengths produced by the studied additive manufacturing, and (3) developing and implementing an effective process modeling procedure to achieve intermetallic-free aluminum-steel bimetallic structures. The primary complexity is how to effectively interrelate nanoscale bonding phenomena between dissimilar metals to a macro-scale thermomechanical interactions. To address this challenge, the following multidisciplinary approaches will be pursued: (1) exploring selectively integrated molecular-dynamic and continuum-mechanics based models to reveal the nanoscale deformation and material responses at the interface, (2) performing in-situ process monitoring and interfacial microstructure analysis to guide the multi-physics simulation model and advance the scientific understanding of solid-state metal additive manufacturing, and (3) validating computational procedures using a laboratory setup and evaluating the bond strength of additively produced bimetallic components.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.