Additive manufacturing (AM), also known as 3D printing, is a next generation technology for cost-effective and accelerated way of manufacturing complex-shaped metallic components by successively adding and melting layers of alloy powder directly controlled by a 3D computer-aided design dataset. It has many critical applications in NASA missions such as those found in propulsion and spacecraft. Prior to acceptance of AM processes by NASA, other government agency, and commercial space missions, however, a longstanding technical challenge is the qualification and certification of AM processes and systems for critical, high-value metallic components. The main objective of the proposed research is to develop a physics-based, predictive modeling approach for a rigorous yet efficiency way of certification of AM processing parameters, alloy composition, and resulting microstructures for the desired properties of metallic components via Laser-Powder Bed Fusion (L-PBF) AM process. Particularly, an integrated process-microstructure models will make it attainable for significantly new capable for multiple laser passes, drastically improving the relevance of process-microstructure models to actual AM production scenario.