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Eun-Ji Cha 2 Articles
Optimization of VIGA Process Parameters for Power Characteristics of Fe-Si-Al-P Soft Magnetic Alloy using Machine Learning
Sung-Min Kim, Eun-Ji Cha, Do-Hun Kwon, Sung-Uk Hong, Yeon-Joo Lee, Seok-Jae Lee, Kee-Ahn Lee, Hwi-Jun Kim
J Powder Mater. 2022;29(6):459-467.   Published online December 1, 2022
DOI: https://doi.org/10.4150/KPMI.2022.29.6.459
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Soft magnetic powder materials are used throughout industries such as motors and power converters. When manufacturing Fe-based soft magnetic composites, the size and shape of the soft magnetic powder and the microstructure in the powder are closely related to the magnetic properties. In this study, Fe-Si-Al-P alloy powders were manufactured using various manufacturing process parameter sets, and the process parameters of the vacuum induction melt gas atomization process were set as melt temperature, atomization gas pressure, and gas flow rate. Process variable data that records are converted into 6 types of data for each powder recovery section. Process variable data that recorded minute changes were converted into 6 types of data and used as input variables. As output variables, a total of 6 types were designated by measuring the particle size, flowability, apparent density, and sphericity of the manufactured powders according to the process variable conditions. The sensitivity of the input and output variables was analyzed through the Pearson correlation coefficient, and a total of 6 powder characteristics were analyzed by artificial neural network model. The prediction results were compared with the results through linear regression analysis and response surface methodology, respectively.

Micro-deformation behavior of Brittle Hf-based Metallic Glass during Mechanical Milling
Song-Yi Kim, A-Young Lee, Eun-Ji Cha, Do-Hun Kwon, Sung-Uk Hong, Min-Woo Lee, Hwi-Jun Kim, Min-Ha Lee
J Powder Mater. 2018;25(3):246-250.   Published online June 1, 2018
DOI: https://doi.org/10.4150/KPMI.2018.25.3.246
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In this study, we investigate the deformation behavior of Hf44.5Cu27Ni13.5Nb5Al10 metallic glass powder under repeated compressive strain during mechanical milling. High-density (11.0 g/cc) Hf-based metallic glass powders are prepared using a gas atomization process. The relationship between the mechanical alloying time and microstructural change under phase transformation is evaluated for crystallization of the amorphous phase. Planetary mechanical milling is performed for 0, 40, or 90 h at 100 rpm. The amorphous structure of the Hf-based metallic glass powders during mechanical milling is analyzed using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Microstructural analysis of the Hf-based metallic glass powder deformed using mechanical milling reveals a layered structure with vein patterns at the fracture surface, which is observed in the fracture of bulk metallic glasses. We also study the crystallization behavior and the phase and microstructure transformations under isothermal heat treatment of the Hf-based metallic glass.


Journal of Powder Materials : Journal of Powder Materials