CAREER: Understanding Bond Formation, Microstructural Development and Mechanical Properties in Cold Spray Additive Manufacturing – A Unified Experimental and Numerical Approach

基于熔融的增材制造（AM）已被用于高价值金属部件制造。然而，由于高的工艺温度（通常超过组分材料的熔点）以及大的相关热梯度和快速冷却速率，存在限制。另一方面，诸如冷喷涂技术之类的非熔融金属增材制造，其中微小的粉末颗粒被加速到超音速以在冲击时碰撞、结合到底层材料并在底层材料上堆积，可以大大减轻熔融根源的挑战。该学院早期职业发展（CAREER）奖支持研究开发冷喷涂AM的工艺-微观结构-性能关系的基本理解，使用新型高速单颗粒冲击测试，辅以多尺度数值建模，研究单个粘结颗粒，冷喷涂工艺的构建模块，然后扩展到零件级研究。该研究将为冷喷涂增材制造提供可靠和以性能为导向的工艺设计，并有可能通过在需要时实现可持续和敏捷的制造和维修来加强国防和其他行业。所获得的知识也可以转化为航空航天、建筑和能源应用的其他固态连接或增材技术。该团队将通过设计的增材制造工具包进行实践活动，吸引K-12学生和教育工作者。该项目还将通过为期10周的夏令营促进少数民族学生参与先进制造业。该CAREER项目的总体目标是建立一个统一的框架，以了解和预测冷喷涂沉积物的临界速度，冲击引起的微观结构发展，微观尺度的结合强度和宏观尺度的机械性能。将进行激光诱导微尺度射弹撞击试验，并进行高分辨率成像，以产生轮廓分明的高速单个粘结颗粒，其微观结构和性能将通过先进的电子显微镜和微机械测量进行表征。第一层的影响和粒子对后续层的影响将进行系统的研究。将科学地揭示冲击速度、氧化层厚度、颗粒尺寸和温度以及冲击角度在粘结界面和局部粘结强度特性中的作用。此外，将建立有限元建模，结合基于位错的本构模型，氧化层断裂，和内聚键合，这将被用来预测的冲击引起的微观结构的变化和粘结强度。微观尺度的模拟将通知一个宏观尺度的模型来计算冷喷涂试样的机械性能。在多尺度模型中还将考虑颗粒尺寸、温度和氧化层厚度分布导致的不同统计效应来源。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。

Melting-based additive manufacturing (AM) has been utilized for high-value metallic component manufacture. Limitations exist, however, due to the high process temperatures, (often beyond the melting point of component materials), and the large associated thermal gradients and rapid cooling rates. On the other hand, non-melting metal AM such as cold spray technology, in which tiny powder particles are accelerated to a supersonic speed to collide, bond to and build up underlying materials upon impact, may considerably alleviate the melting-rooted challenges. This Faculty Early Career Development (CAREER) award supports research in developing a fundamental understanding of the process-microstructure-property relationships for cold spray AM using novel high-speed single-particle impact testing, complemented by multi-scale numerical modeling, to study individual bonded particles, the building blocks of the cold spray process, and then expand to a part-level study. The research will enable reliable and performance-oriented processing design for cold spray AM, with a potential to strengthen the Nation’s defense and other industries through enabling sustainable and agile manufacturing and repair at the point of need. The knowledge gained may also be translated to other solid-state joining or additive technologies for aerospace, construction and energy applications. The team will engage K-12 students and educators through hands-on activities with a designed additive manufacturing toolkit. The project will also promote participation from underrepresented minority students in advanced manufacturing through 10-week summer camps in a research laboratory.The overall goal of this CAREER project is to establish a unified framework to understand and predict the critical velocity, impact-induced microstructural development, micro-scale bond strength, and macro-scale mechanical properties of cold-sprayed deposits. Laser-induced micro-scale projectile impact testing will be conducted with high-resolution imaging to produce well-defined high-velocity individual bonded particles, with microstructures and properties characterized by advanced electron microscopy and micro-mechanical measurements. Both the first layer impacts and particle impacts on subsequent layers will be systematically investigated. The role of the impact velocity, oxide layer thickness, particle size and temperature, and impact angle in the characteristics of bonded interfaces and local bond strengths will be scientifically revealed. Further, finite element modeling incorporating a dislocation-based constitutive model, oxide layer fracture, and cohesive bonding will be established, which will be used to predict the impact-induced microstructure changes and bond strengths. The micro-scale simulations will inform a macro-scale model to calculate the mechanical properties of cold-sprayed specimens. Different sources of statistical effects resulting from the distribution of particle sizes, temperatures, and oxide layer thicknesses will also be considered in the multi-scale model.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.