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

通过在给定基底上沉积特定材料来进行异种合金的增材制造，有可能实现具有所需性能和功能的有效轻质结构。铝-钢复合构件由于其可获得性和可承受性而在工程结构应用中具有强烈的兴趣。然而，使用目前现有的制造方法在铝合金和钢之间直接结合常常导致界面处的有害金属间化合物，从而显著降低结合强度。该奖项将解决基于摩擦的新型固态增材制造工艺的基础研究，在此过程中，由于高应变率，在不同金属界面处的局部剪切变形可能使加工合金非晶化并抑制金属间化合物的形成。然而，如何原子水平的扩散在晶界的局部变形相互作用，并抑制金属间化合物的形成是一个关键的知识差距，阻碍充分理解这样一个复杂的物理现象。对这项研究的深入了解不仅将揭示通过固态增材制造推进异种合金连接所需的关键知识，还将使高性能铝-钢复合材料部件制造的实现和商业化实现快速过渡。在整个项目中，研究材料将被纳入先进制造的几个本科生和研究生课程，以培养下一代工程师应对未来制造业的挑战。该项目的具体研究目标包括：（1）阐明高应变率固态增材制造中的非晶化机制和金属间化合物形成，其控制接合的铝-钢界面处的结合完整性，（2）研究关键工艺参数在确定由所研究的增材制造产生的铝-钢界面结合强度中的作用，以及（3）开发并实施有效的工艺建模程序以实现无金属间化合物的铝-钢复合结构。主要的复杂性是如何有效地将不同金属之间的纳米级键合现象与宏观尺度的热机械相互作用联系起来。为应对这一挑战，将采取以下多学科办法：（1）探索选择性集成的基于分子动力学和连续力学的模型，以揭示界面处的纳米级变形和材料响应，（2）进行原位过程监测和界面微观结构分析，以指导多物理场仿真模型并推进对固态金属增材制造的科学理解，以及（3）使用实验室设置验证计算程序，并评估增材制造的粘结剂组件的粘结强度。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值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.