Journal of Powder Materials

Cheon-Hee Bok

3 Articles

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

Consolidation and Mechanical Property of Rapidly Solidified Al-20 wt% Si Alloy Powders by Continuous Equal Channel Multi-Angular Pressing: Seung-Chae Yoon, Cheon-Hee Bok, Min-Hong Seo, Soon-Jik Hong, Hyoung-Seop Kim; J Korean Powder Metall Inst. 2008;15(1):31-36.; DOI: https://doi.org/10.4150/KPMI.2008.15.1.031

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In this study, the bottom-up powder metallurgy and the top-down severe plastic deformation (SPD) techniques for manufacturing bulk nanomaterials were combined in order to achieve both full density and grain refinement without grain growth of rapidly solidified Al-20 wt% Si alloy powders during consolidation processing. Continuous equal channel multi-angular processing (C-ECMAP) was proposed to improve low productivity of conventional ECAP, one of the most promising method in SPD. As a powder consolidation method, C-ECMAP was employed. A wide range of experimental studies were carried out for characterizing mechanical properties and microstructures of the ECMAP processed materials. It was found that effective properties of high strength and full density maintaining nanoscale microstructure are achieved. The proposed SPD processing of powder materials can be a good method to achieve fully density and nanostructured materials.

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X-ray diffraction study on the microstructure of a Mg–Zn–Y alloy consolidated by high-pressure torsion
Péter Jenei, Jenő Gubicza, Eun Yoo Yoon, Hyoung Seop Kim
Journal of Alloys and Compounds.2012; 539: 32. CrossRef
Microstructures and mechanical properties of Mg–Zn–Y alloy consolidated from gas-atomized powders using high-pressure torsion
Eun Yoo Yoon, Dong Jun Lee, Taek-Soo Kim, Hong Jun Chae, P. Jenei, Jeno Gubicza, Tamas Ungár, Milos Janecek, Jitka Vratna, Sunghak Lee, Hyoung Seop Kim
Journal of Materials Science.2012; 47(20): 7117. CrossRef
Synthesis and microstructure control of Mg alloy powder composites by multi-extrusion
Taek-Soo Kim, Hong Jun Chae, Sun-Mi Kim, Hanshin Choi, Hye Sung Kim
Journal of Alloys and Compounds.2011; 509: S247. CrossRef

Finite Element Analysis on the Effect of Die Corner Angle in Equal Channel Angular Pressing Process of Powders: Seung-Chae Yoon, Cheon-Hee Bok, Pham Quang, Hyoung-Seop Kim; J Korean Powder Metall Inst. 2007;14(1):26-31.; DOI: https://doi.org/10.4150/KPMI.2007.14.1.026

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Manufacturing bulk nanostructured materials with least grain growth from initial powders is challenging because of the bottle neck of bottom-up methods using the conventional powder metallurgy of compaction and sintering. In this study, bottom-up type powder metallurgy processing and top-down type SPD (Severe Plastic Deformation) approaches were combined in order to achieve both real density and grain refinement of metallic powders. ECAP (Equal Channel Angular Pressing), one of the most promising processes in SPD, was used for the powder consolidation method. For understanding the ECAP process, investigating the powder density as well as internal stress, strain distribution is crucial. We investigated the consolidation and plastic deformation of the metallic powders during ECAP using the finite element simulations. Almost independent behavior of powder densification in the entry channel and shear deformation in the main deformation zone was found by the finite element method. Effects of processing parameters on densification and density distributions were investigated.

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Finite element analysis of the bending behavior of a workpiece in equal channel angular pressing
Seung Chae Yoon, Anumalasetty Venkata Nagasekhar, Hyoung Seop Kim
Metals and Materials International.2009; 15(2): 215. CrossRef

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