I am an assistant professor at Osaka University, researching atomic arrangements of amorphous (glass) and liquids, and their crystallization processes. Currently, I'm mainly studying 3D Additive Manufacturing process development based on experimental observations, computer simulations, and machine learning analysis. 

2023 March

Our research result has been published in the Computational Materials Science journal that describes a method for estimating physical properties (such as interfacial energy) in eutectic solidification by combining data assimilation, a machine learning method, with phase field (PF) simulation.

   The phase field method can effectively predict the microstructure formation of eutectic alloys. However, to reproduce the experimentally observed microstructure, a large number of simulation parameters must be correctly determined for each alloy system. In this study, we proposed a data assimilation method based on ensemble Kalman filter to determine his PF simulation parameters for unidirectional solidification of eutectic alloys by optimizing data assimilation conditions. Numerical twinning experiments revealed that the eutectic microstructure could be reproduced, but the four His PF simulation parameters remained unknown. We also investigated appropriate experimental observation conditions for estimating simulation parameters and found that a sufficient observation frequency could be determined from the solid-liquid interfacial velocity.

   Based on these results, we are currently investigating on parameter estimation through data assimilation using in-situ observation experiment data.

• Data assimilation for phase-field simulations of the formation of eutectic alloy microstructures, Y. Seguchi, M. Okugawa, C. Zhu, A. Yamanaka, Y. Koziumi, Comput. Mater. Sci. 237 (2024) 112910. https://doi.org/10.1016/j.commatsci.2024.112910.

2023 January

Our research results have been published in Materials Transactions. This is the result of the research I started after moving to Osaka University, investigating the behavior of powder in the AM PBF process using the discrete element method (DEM). This research was conducted using a method similar to the molecular dynamics calculations that I have been doing for many years. Optimization of the powder layer formation process on a simulation basis is expected.

• Raking process for Powder Bed Fusion of Ti-6Al-4V alloy Powder Analyzed by Discrete Element Method, M. Okugawa, Y. Isono, Y. Koizumi, T. Nakano, Materials Transactions, Vol. 64, No. 1 (2023) pp. 37-43. [View on-line]  

2022 November 10

Our research results were published in Materials. This paper proposes from a phase-field crystal growth simulation that it is possible to achieve ultra-fine grain structure by utilizing unique intrinsic heterogeneous nucleation in metal 3D printing of Al-Si eutectic alloys. . By expanding the concept of crystal structure design in metal 3D printing, it is expected to create higher-performance metal 3D printed parts.

• Effect of Rapid Heating and Cooling Conditions on Microstructure Formation in Laser Powder-bed fusion of Al-Si Hypoeutectic Alloy: A Phase-Field Study, M. Okugawa, Y. Furushiro, Y. Koizumi,Materials, 15 (17), 6092. [View on-line]

2022 November 4

The research result were published in Nature Communication. In intermetallic compounds, formation of a fine porous structure was found by the molten metal de-alloying method, and the peculiar ligament growth mechanism in the experiment was supported by the calculation of the atomic diffusion coefficient by molecular dynamics simulation.

• Ultrafine Nanoporous Intermetallic Catalysts by High-Temperature Liquid Metal Dealloying for Electrochemical Hydrogen Production, R. Song, J. Han, M. Okugawa, R. Belosludov, T. Wada, J. Jiang, D. Wei, A. Kubo, Y. Tian, H. Kato, M. Chen, Nature Communication, 13, (2022) 5157. [View on-line]