Journal of Powder Materials

Byong-Sun Chun

7 Articles

Fabrication of Fe coated Mg Based Desulfurization Powder by Mechanical Alloying Process: Joon-Woo Song, Otaduy Guillermo, Byong-Sun Chun, Soon-Jik Hong; J Korean Powder Metall Inst. 2012;19(3):226-231.; DOI: https://doi.org/10.4150/KPMI.2012.19.3.226

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Abstract PDF: In this research, the coating behavior of Mg and Fe desulfurization powder fabricated by low energy and conventional planetary mill equipment was investigated as a function of milling time, which produces uniform Fe coated powders due to milling energy. Since high energy ball milling results in breaking the Fe coated Mg powders into coarse particles, low energy ball milling was considered appropriate for this study, and can be implemented in desulfurization industry widely. XRD and FE-SEM analyses were carried out to investigate the microstructure and distribution of the coating material. The thickness of the Fe coating layer reaches a maximum of 14 µm at 20 milling hours. The BCC structures of Fe particles are deformed due to the slip system of Fe coated Mg particles.

Synthesis and Characterization of (AgSbTe₂)₁₅(GeTe)₈₅ Thermoelectric Powder by Gas Atomization Process: Hyo-Seob Kim, Jin-Kyu Lee, Jar-Myung Koo, Byong-Sun Chun, Soon-Jik Hong; J Korean Powder Metall Inst. 2011;18(5):449-455.; DOI: https://doi.org/10.4150/KPMI.2011.18.5.449

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In this study, p-type (AgSbTe_2)_15(GeTe)_85: TAGS-85 compound powders were prepared by gas atomization process, and then their microstructures and mechanical properties were investigated. The fabricated powders were of spherical shape, had clean surface, and illustrated fine microstructure and homogeneous AgSbTe_2 + GeTe solid solution. Powder X-ray diffraction results revealed that the crystal structure of the TAGS-85 sample was single rhombohedral GeTe phase, which with a space group R_3m. The grain size of the powder particles increased while the micro Vickers hardness decreased with increasing annealing temperature within the range of 573 K and 723 K due to grain growth and loss of Te. In addition, the crystal structure of the powder went through a phase transformation from rhombohedral (R_3m) at low-temperature to cubic (F_m-3m) at high-temperature with increasing annealing temperature. The micro Vickers hardness of the as-atomized powder was around 165 Hv, while it decreased gradually to 130 Hv after annealing at 673K, which is still higher than most other fabrication processes.

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Thermoelectric properties of n-type Bi2Te3 alloys produced by a combined process of magnetic pulsed compaction (MPC) and spark plasma sintering (SPS)
Chul-Hee Lee, M. Fatih Kilicaslan, Babu Madavali, Soon-Jik Hong
Research on Chemical Intermediates.2014; 40(7): 2543. CrossRef

Phase Transformation and Microstructure of FeSi₂ Thermoelectric Compounds Manufactured by Powder Metallurgy: Kyoung-Tae Park, Jin-Gyo Shin, Soon-Jik Hong, Byong-Sun Chun; J Korean Powder Metall Inst. 2010;17(6):482-488.; DOI: https://doi.org/10.4150/KPMI.2010.17.6.482

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Abstract PDF: In this study, FeSi_2 as high temperature performance capable thermoelectric materials was manufactured by powder metallurgy.The as-casted Fe-Si alloy was annealed for homogenization below 1200°C for 3 h. Due to its high brittleness, the cast alloy transformed to fine powders by ball-milling, followed by subsequent compaction (hydraulic pressure; 2 GPa) and sintering (1200°C, 12 h). In order to precipitate beta-FeSi_2, heat treatment was performed at 850°C with varying dwell time (7, 15 and 55 h). As a result of this experiment thermoelectric phase beta-FeSi_2 was quickly transformed by powder metallurgical process. There was not much change in powder factor between 7h and 55h specimens.

Effect of Ball milling Time on Graphite Dispersion and Mechanical Properties in Rapidly Solidified 6061 Al Composite: Hyeon-Taek Son, Jae-Seol Lee, Soon-Jik Hong, Byong-Sun Chun; J Korean Powder Metall Inst. 2009;16(3):209-216.; DOI: https://doi.org/10.4150/KPMI.2009.16.3.209

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A composite of rapidly solidified Al-6061 alloy powder with graphite particle reinforcements was prepared by ball milling and subsequent hot extrusion. The microstructure and mechanical properties of these composites were investigated as a function of milling time. With increasing milling time, the gas atomized initially and spherical powders became elongated with a maximum aspect ratio after milling for 30 h. Then, refinement and spheroidization were achieved by further milling to 70 h with a homogeneous and fine dispersion of graphite particles forming between the matrix alloy layers. The best compression and wear properties were obtained in the powder milled for 70 h, associated with the increased fine and homogeneous distribution of graphite particles in the aluminum alloy matrix.

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Fabrication of Fe coated Mg Based Desulfurization Powder by Mechanical Alloying Process
Joon-Woo Song, Otaduy Guillermo, Byong-Sun Chun, Soon-Jik Hong
Journal of Korean Powder Metallurgy Institute.2012; 19(3): 226. CrossRef

Analysis of Densification Behavior during Powder Equal Channel Angular Pressing using Critical Relative Density Model: Cheon-Hee Bok, Ji-Hoon Yoo, Seung-Chae Yoon, Taek-Soo Kim, Byong-Sun Chun, Hyoung-Seop Kim; J Korean Powder Metall Inst. 2008;15(5):365-370.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.365

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In this study, bottom-up powder processing and top-down severe plastic deformation processing approaches were combined in order to achieve both full density and grain refinement with least grain growth. The numerical modeling of the powder process requires the appropriate constitutive model for densification of the powder materials. The present research investigates the effect of representative powder yield function of the Shima-Oyane model and the critical relative density model. It was found that the critical relative density model is better than the Shima-Oyane model for powder densification behavior, especially for initial stage.

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Analysis of Densification Behavior of Magnesium Powders in Extrusion using the Critical Relative Density Model
Seung-Chae Yoon, Hong-Jun Chae, Taek-Soo Kim, Hyoung-Seop Kim
Journal of Korean Powder Metallurgy Institute.2009; 16(1): 50. CrossRef

Finite Element Analysis of Densification Behavior during Equal Channel Angular Pressing Process of Powders: Seung-Chae Yoon, Pham Quang, Byong-Sun Chun, Hong-Ro Lee, Hyoung-Seop Kim; J Korean Powder Metall Inst. 2006;13(6):415-420.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.415

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Abstract PDF: Nanostructured metallic materials are synthesized by bottom-up processing which starts with powders for assembling bulk materials or top-down processing starting with a bulk solid. A representative bottom-up and top-down paths for bulk nanostructured/ultrafine grained metallic materials are powder consolidation and severe plastic deformation (SPD) methods, respectively. In this study, the bottom-up powder and top-down SPD approaches were combined in order to achieve both full density and grain refinement without grain growth, which were considered as a bottle neck of the bottom-up method using conventional powder metallurgy of compaction and sintering. For the powder consolidation, equal channel angular pressing (ECAP), one of the most promising method in SPD, was used. The ECAP processing associated with stress developments was investigated. ECAP for powder consolidation were numerically analyzed using the finite element method (FEM) in conjunction with pressure and shear stress.

Elevated Temperature Strength and Microstructure of Atomized and Ball-milled Al-xFe-yCr Alloys: Kyeong-Hwan Kim, Byong-Sun Chun; J Korean Powder Metall Inst. 2000;7(4):197-204.

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Abstract PDF: Gas atomization mechanical alloying and hot pressing have successfully made high temperature Al-9.45Fe-4.45Cr alloy. The microstructure and mechanical properties of this alloy has been studied by using optical microscope, scanning electron microscope, transmission electron microscope, X-ray diffractometer and compressive tester. It contains high concentration of transition elements of Fe and Cr, which form thermally stable dispersoids in the aluminum matrix. Proper oxidation of powders during ball milling strengthens the bulk extrudates by providing the obstacle particles. The oxide particles are very chemically and thermally stable and prevent the coarsening of the intermediate compounds.

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