2, Yuheng Liu3, Takayoshi Nakano1 Yuichiro Koizumi1, Masayuki Okugawa 1Professor, 2Assistant Professor, 3Specially-appointed Professor, Osaka University, Japan 30Digital Twin Science of Powder Bed Fusion Invited Talk S2-2 Metal additive manufacturing (AM), Powder Bed Fusion (PBF), can control not only the geometry but also microstructures from single crystal-like structure to fine grains by the control of solidification conditions. Solidification conditions can be tuned by the process parameters, such as beam power, scanning speeds, etc. There have been various interesting phenomena related to crystal growth as in PBF. They are quite different from those in conventional solidification process. Since the phenomenon occurs very rapidly in a narrow space, it is challenging to observe experimentally and elucidate their details despite the extensive experimental studies. Thus, computer simulations are commonly used. Computational fluid dynamics simulations elucidated that the cooling rate can be as high as 106 K/s. Even with such a high cooling rate, PBF can form single-crystal-like columnar grains. This is attributed to the extremely high temperature gradient of around 107 K/m at solidification front. On the other hand, the possibility of absolute stability needs to be taken into account for a very fast solidification rate over approximately 1 m/s. On the other hand, recently, cyberspace replicas of a system are called digital twin (DT). In general, a DT is utilized to predict phenomena occurring in the system and optimize control parameters. We propose to use a DT to elucidate the unique solidification mechanisms occurring in PBF, and we propose to define the applications of DT for obtaining scientific knowledge as “digital twin science (DTS).” In this presentation we introduce our recent studies on computer simulations and process monitoring relevant to PBF process with a special focus on the relationship between the extreme condition characteristic of the PBF process and solidification microstructures. For instance, we have elucidated the unique relationship between solidification conditions and the tendency of equiaxed grains and epitaxially grown columnar grains in the microstructures formed by electron beam irradiation on stainless steel, and laser irradiation on eutectic Al-Si alloy. Moreover, we demonstrated the repetition of epitaxial growth in laser-PBF with narrow pitch results in the formation of single crystals. Lastly, we present our recent challenges to extract information of melt-pool from the data obtained via the monitoring system consisting of on-axis and off-axis dual photodiodes, paving the way for real-time in-process examination of crystal orientation and microstructure. Accumulation of the data and knowledges DTS approach will open up a new horizon for the future technologies to create materials with desired properties with confidence, advancing the frontier of metal AM. o Abstract Session 2 ｜Yuichiro Koizumi earned his Ph.D. in 1999 from the Department of Materials Science at Osaka University. He subsequently joined the Department of Adaptive Machine Systems at Osaka University as an Assistant Professor. Later, he spent a year as a visiting scientist in the Department of Materials Science and Engineering at the Massachusetts Institute of Technology (MIT). In 2010, he became an Associate Professor at the Institute for Materials Research, Tohoku University, Sendai, Japan. By 2018, he was appointed as a professor in the Division of Materials and Manufacturing Science, Graduate School of Engineering at Osaka University, where he oversees research in Materials Design and Processing. To date, he has published approximately 200 papers. NIMS Award Symposium 2023 High-temperature MaterialsMetal Additive Manufacturing
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