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

通过在给定的衬底上沉积特定的材料来添加制造不同的合金，有可能获得具有所需性能和功能的有效的轻质结构。铝-钢双金属构件由于其可获得性和可负担性，在工程结构应用中引起了极大的兴趣。然而，使用现有的制造方法直接连接铝合金和钢往往会在界面上产生有害的金属间化合物，从而显著降低结合强度。该奖项将致力于一种新型摩擦型固态添加剂制造工艺的基础研究，在此过程中，由于高应变率，不同金属界面上的局部剪切变形可能会使处理后的合金非晶化，并抑制金属间化合物的形成。然而，双金属界面的原子能级扩散如何与局域形变相互作用并抑制金属间化合物的形成，是阻碍人们充分理解这种复杂物理现象的关键知识缺口。通过这项研究的深入了解，不仅将揭示通过固态添加剂制造连接不同合金所需的关键知识，而且还将使高性能铝-钢双金属部件制造的实现和商业化快速过渡。该项目的具体研究目标包括：(1)阐明高应变率固态添加剂制造中的非晶化机制和金属间化合物的形成，这支配着铝-钢连接界面的结合完整性；(2)研究关键工艺参数在决定所研究的添加剂制造产生的铝-钢界面结合强度中的作用；以及(3)开发和实施有效的工艺模拟程序，以获得无金属间化合物的铝-钢双金属结构。主要的复杂性是如何有效地将不同金属之间的纳米尺度结合现象与宏观尺度的热机械相互作用联系起来。为了应对这一挑战，将采取以下多学科方法：(1)探索基于选择性集成的分子动力学和连续介质力学的模型，以揭示界面上的纳米级变形和材料响应；(2)执行现场过程监控和界面微结构分析，以指导多物理模拟模型，并促进对固态金属添加剂制造的科学理解；以及(3)使用实验室设置验证计算程序，并评估添加生产的双金属组件的结合强度。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。

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.