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Dong-Wan Lee 2 Articles
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[English]
Selective Laser Sintering of Co-Cr Alloy Powders and Sintered Products Properties
Dong-Wan Lee, Minh-Thuyet Nguyen, Jin-Chun Kim
J Powder Mater. 2023;30(1):7-12.   Published online February 1, 2023
DOI: https://doi.org/10.4150/KPMI.2023.30.1.7
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Metal-additive manufacturing techniques, such as selective laser sintering (SLS), are increasingly utilized for new biomaterials, such as cobalt-chrome (Co-Cr). In this study, Co-Cr gas-atomized powders are used as charge materials for the SLS process. The aim is to understand the consolidation of Co-Cr alloy powder and characterization of samples sintered using SLS under various conditions. The results clearly suggest that besides the matrix phase, the second phase, which is attributed to pores and oxidation particles, is observed in the sintered specimens. The as-built samples exhibit completely different microstructural features compared with the casting or wrought products reported in the literature. The microstructure reveals melt pools, which represent the characteristics of the scanning direction, in particular, or of the SLS conditions, in general. It also exposes extremely fine grain sizes inside the melt pools, resulting in an enhancement in the hardness of the as-built products. Thus, the hardness values of the samples prepared by SLS under all parameter conditions used in this study are evidently higher than those of the casting products.

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[English]
Microstructure and Properties Comparison of Pure Cu and Cu-5 wt.% Al2O3 Composite Processed by Spark Plasma Sintering
Dinh Van Cong, Dong-Wan Lee, Su-Wan Lee, Nguyen Minh Thuyet, Nguyen Viet Hoang, Jin-Chun Kim
Received December 3, 2025  Accepted February 25, 2026  Published online February 26, 2026  
DOI: https://doi.org/10.4150/jpm.2025.00472
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AbstractAbstract
This study compares the microstructure and properties of pure Cu and Cu-5 wt.% Al2O3 composites fabricated by spark plasma sintering under strictly identical processing conditions at 800-1000 °C. Pure Cu samples achieved near-full densification and exhibited a bimodal grain structure dominated by coarse grains with increasing sintering temperature. In contrast, the composite samples showed lower density and non-monotonic densification behavior, with a minimum relative density at 900 oC and significantly refined equiaxed grains due to strong grain-boundary pinning by nano Al2O3 particles. The higher fractions of high-angle boundaries and pronounced orientation disruption were observed in the composite samples, while high-resolution analysis confirmed the presence of grain-boundary Al2O3-rich regions that restricted Cu grain coalescence and continuity of grain boundary migration. X-ray diffraction results confirmed the absence of reaction phases in both materials. Hardness peaked at 900 °C for both samples, and the composite samples showed consistently lower hardness due to retained porosity. The apparent electrical conductivity of the composite displays a non-linear temperature dependence, reflecting the competing influences of densification, microstructural recovery, and the insulating nature of Al2O3.

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