Phase Field Crystal Simulation of Grain Growth in BCC Metals during Additive Manufacturing
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Phase Field Crystal Simulation of Grain Growth in BCC Metals during Additive Manufacturing Hang Ke and Ioannis Mastorakos Department of Mechanical and Aeronautical Engineering, Clarkson University, Potsdam, NY 13699, USA ABSTRACT In this work, we demonstrate that the phase field crystal (PFC) method can be applied to identify and predict the microstructure evolution during the solidification of the BCC metals in additive manufacturing. The results reveal the columnar structure of the grains, which matches the grain growth observed in real samples produced with the additive manufacturing technique. The effect of ambient temperature, seed-seed distance and seed-seed misorientation on the grain growth has been investigated. In addition, the formation of crystal defects during the process is recorded and the resulted long-range stresses are calculated using the eigenstresses theory. INTRODUCTION Additive manufacturing, also known as 3D printing, is rising popularity during the last few years due to its wide applications in various industrial areas. In additive manufacturing metallic powders are deposited, one layer at the time, on a substrate bed and melted to produce the desired geometry [1]. Researchers and engineers are optimistic that this future technology can fulfill the dreams of designing and fabricating in house any part or component with the support of computer aided design (CAD) [2]. However, despite all the progress that has been made, not enough emphasis has been given to the microstructures of the build parts, which is actually very significant to the properties and performance of the final product. The microstructure and mechanical properties of the build part can be affected by the process parameters, such as laser beam power, beam scan speed, powder feed rate, powder layer thickness and preheat temperature, during the solidification part in additive manufacturing [3]. To control and model the whole solidification process, knowing the influence of these parameters to the microstructure of the final part is really important. Many computational approaches have arisen to simulate microstructure evolution of materials. One of the most popular methods is the phase field (PF) approach. Sahoo and Chou [4] developed a PF model of the microstructure evolution of the Ti-6Al-4V alloy in electron beam additive manufacturing process. They incorporated the temperature gradient and solidification velocity as the simulation parameters, and showed that columnar dendritic spacing and width of dendrites decreases with the increase in temperature gradient and beam scan speed. Kundin et al. [5] studied the microstructure formation of Inconel 718 superalloy using PF model. They evaluated the model via comparison to Green-function calculations and Kurz-Fisher model predictions. Krivyilov et al. [6] developed a PF model of metal powder consolidation and tested with the carbonyl iron powder. Their simulations showed a good agreement with the experimental data in the consolidation time. Recently, a new approach to PF method appea
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