Phase Field Modeling of Thermal Transport for Predicting and Preventing Porosity and Solidification Cracking in Additive Manufacturing

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This project considers the geometry accuracy and mechanical quality of high-end additively manufactured metal products used in aerospace, automobile, naval, petroleum, and energy industries. Basic understanding of the high temperature process such as how laser heating interacts with metallic powders and how surface defects evolve during powder melting and fusion is key to the success of additive manufacturing. Through theoretical analysis and experimental validation, this project focuses on predicting and preventing the formation of surface defects including solidification cracks. The project will help manufacturing industry in the U.S. to develop strategies to increase mechanical performance of critical metallic parts made by additive manufacturing. Specifically, this project will benefit metallic material suppliers, manufacturing machine designers, product designers and end users. Higher education and workforce training with diversity are emphasized for the next generation of engineers in manufacturing field. The primary road block on additive manufacturing of high strength alloys is geometric accuracy, surface quality, and the quest for mechanical performance. Defects such as pores, notches, and cracks in additive manufacturing are often caused by incomplete melting of powders, interfacial instability, evaporating and recoiling, balling, spattering, and cracking during solidification. There is a great need on predictive modeling of the process dynamics at powder and microstructure levels to mitigate defects caused by above mechanisms. The project goal is to establish an integrated phase field theoretical framework for this purpose. The project includes three specific tasks: (i) resolve the dynamics and distribution of porosity by a fully coupled thermal, fluids, phase transition, and microstructure evolution model, (ii) integrate thermal fluid dynamics with elasticity, plasticity, grain microstructure evolution, and susceptibility of solidification cracking, (iii) perform experimental validations and uncertainty analysis using available data from NIST Additive Manufacturing Benchmark Test Series (AM-Bench) ranging from microstructure to thermal mechanical analysis.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.