Numerical investigation of dissimilar material interfaces in multi-material LPBF process

Multi-material laser powder bed fusion (LPBF) is a major advancement in additive manufacturing, enabling the production of components with spatially varied properties and tailored functionalities. This capability supports the development of novel alloys and complex, multifunctional structures with enhanced performance characteristics. A critical aspect of multi-material LPBF is the transition zone, where material interaction and fusion occur, directly influencing the mechanical properties, structural integrity, and overall performance of the printed component. However, challenges at the interface, or fusion zone, include macro-segregation of alloying elements leading to chemical inhomogeneity, as well as thermophysical property mismatches that contribute to defects such as pores, cracks, and lack of fusion. Also, microstructural evolution in the transition zone plays a crucial role in determining the final part’s mechanical properties, as solute segregation impacts strength, ductility, corrosion resistance.
To address these challenges, a comprehensive understanding of the fundamental physics governing multi-material LPBF is essential. Numerical modeling offers valuable insights into the complex mechanisms of heat transfer, material flow, solidification dynamics, and phase transformations. This thesis develops a high-fidelity computational fluid dynamics (CFD) model in OpenFOAM to simulate metal mixing within the transition zone under a moving laser heat source, along with a phase-field (PF) model to study the rapid solidification. These numerical models are integrated with experimental studies to (1) address macrosegregation and chemical inhomogeneity, (2) investigate the mechanisms governing defect formation and mitigation strategies at dissimilar material interfaces, and (3) examine microsegregation and microstructural evolution under varying process conditions. This numerical approach provides critical insights into the design of multi-material LPBF systems, improving manufacturability and performance of additively manufactured multi-material components.