Understanding AM Solidification Profile Effects on Material Inhomogenieties, Defects, and Qualification

The research objective of this proposal is to demonstrate feasibility of a solidification science based Integrated Computational Materials Engineering (ICME) that combines computational heat, mass transfer, fluid flow and mechanics simulations with thermodynamic and kinetic models to enable cellular automata (CA) framework. Its purpose is to link the AM laser power bed process parameters with as-built microstructure including phase selection, material inhomogeneities, and the potential for the occurrence of porosity and lack-of-fusion defects. The ICME prediction of 3-D distributions of the thermal gradient (G), interface velocity (R) and the melt pool fluid flow would be utilized as input to the calculation of constitutional supercooling and the columnar-to-equiaxed transition. The dynamics of solidification interface velocity will be modeled using interface response function theories to compute the inhomogeneities caused by phase selection phenomena in metals and alloys. The evolution of the solidification front will be traced within the CA grid to predict the overall solidification grain morphology and texture. ICME will be utilized to detect and/or mitigate the presence of material inhomogeneities. Deposition trials will be performed for two stainless steel alloys to demonstrate the applicability of the solidification based calculation of site-specific microstructure.