CAREER: Understanding Joining Mechanisms in Dissimilar Metal Additive Manufacturing

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This Faculty Early Career Development (CAREER) grant focuses on research to create strong joints between dissimilar alloys, a critical aspect of making multi-alloy components through the laser-based additive manufacturing or three-dimensional (3D) printing process. This approach achieves multi-functional parts with enhanced properties combined in a single component. These components are of particular interest to defense, health, manufacturing, space, and energy sectors where high quality, complex, and customized parts with the most desired performance are needed, which impacts US industry and economy. The research goal is to understand how laser-melting of mixed metals and alloys in a wire-feed, powder-feed process affects the joining of different alloys towards the fabrication of defect-free dissimilar metal components. To achieve this, thermal and fluid flow behavior within the melted dissimilar alloys is studied using computational modeling and experimental processing. This research enables the desired properties in 3D printed multi-material components to be spatially varied. This project aims to integrate research with teaching, mentoring, and training of students at different levels, especially, women and underrepresented minorities. In support of the notion that the Arts activate creative thinking, the project offers summer programs involving hands-on activities based on Art and STEM integration to encourage K-12 students to pursue science and engineering fields.Additive manufacturing (AM) allows for the simultaneous achievement of design freedom and the incorporation of spatially varying properties in the production of multi-material components. The research objective is to gain a comprehensive understanding of the effects of additive manufacturing process physics on dissimilar joining mechanisms. This is achieved by investigating the role of process-induced mixing at the dissimilar alloy interfaces. The central hypothesis is that the microstructure of the mixing-resultant alloy is directly influenced by the degree of process-induced mixing, which, in turn, is governed by thermal fluid flow and thermal history of the melt-pool. This phenomenon is predominantly driven by the combined effects of additive manufacturing process parameters and thermo-physical properties at the dissimilar interface. The researched framework integrates multi-scale, multi-physics modeling with laser-based wire-feed, powder-feed directed energy deposition (DED) fabrication experiments and microstructural analysis. Additionally, DFT and CALPHAD models are created to analyze the thermal history, composition, and melt pool dimensions of the dissimilar melt-pools. This information aids in identifying the specific joining mechanisms in dissimilar metal additive manufacturing, such as bimetallic joints, compositional gradient joints, and transition layer joints. This research advances the field of additive manufacturing to enable the creation of innovative high performance multi-material components with enhanced functionality.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.