Comprehensive studies of SS316L/IN718 functionally gradient material fabricated with directed energy deposition: Multi-physics & multi-materials modelling and experimental validation

Metallic Functionally gradient materials (FGMs) are featured by gradually distributed metallic compositions generating unique mechanical and physical property gradients. As a major metal additive manufacturing process, Directed Energy Deposition (DED) has become an important process for manufacturing multi-materials parts. Fabricating metallic FGMs with the DED process has been studied experimentally in recent years. However, there is a lack of an effective modelling tool to predict the material composition gradients, FGM geometry, and the FGMs building process. The goal of this research is to fill this gap by establishing a novel multi-physics & multi-material thermal fluid model to fundamentally investigate the building process of FGMs with DED. In addition to the thermal distribution, phase change, and molten pool dynamics, the material distribution and geometry of the FGM part can be predicted with the model. As a demonstration, a DED fabrication process for Stainless Steel 316L/Inconel 718 FGM structure was simulated with this modelling tool. After that, the simulation results were validated with experimentally observed material composition and FGM geometry. The novelty of this study is the simulation of FGM part fabricated with DED process by fully considering multiple physics and multiple materials.