Papers by Author: Jin Chun Kim

Abstract: Hypereutectic prealloyed Al-20wt.%Si powders were prepared by the gas atomization process. Characteristics of the atomized Al-Si powders were investigated. With increasing gas pressure of the atomization, the average powder size and oxygen content decreased. Primary Si particles in the as-atomized powders were about 8-10 ㎛. Sintering behavior of the atomized Al-Si powders was discussed with sintering temperature. As-atomized powders were hot-pressed and extruded into a cylindrical shape. 96-99% of theoretical density was achieved by the hot consolidation. Microstructure changes as well as hardness and tensile properties of the samples were evaluated in this paper.

Abstract: To improve the fracture strength and wear resistance of WC-Co cemented carbide, various technologies have been developed related producing the nano crystalline. There have been extensive studied conducted to retard grain growth during liquid phase sintering. However, when this inhibitor is added by simple mixing, a micro-pores forms during sintering In this study, WC-Co nanocrystalline powders with grain growth inhibitor in the site were prepared by MTP (Mechano-Thermic carburizing Process) to minimize this formation of micro pores and to retard grain growth effectively during sintering. In addition, then the phase and grain size of WC-Co nanocrystalline powders were evaluated according to the condition of MTP.

Abstract: The bimodal-structured materials composed of Al-5wt%Mg alloy and its composites reinforced with SiC and Al2O3 particles were prepared by ball-milling and subsequent compaction under the pressure of 350MPa and sintering at temperatures ranging from 973K to 1173K for 1h, 3h and 5h. The macro-interface between Al-Mg and Al-Mg/ Al2O3 composite was macroscopically well-bonded compared to that between Al-Mg and Al-Mg/SiC composite under same sintering conditions. The bonding of macro-interface became better as the sintering time and temperature increased, resulting in that the bimodal-structured materials sintered at 1173K for 5h showed the relative density of nearly 100%. In addition, the higher sintering temperature was, the more irregular macro-interface was. The microhardness of macro-interface area was in between the Al- Mg and composites, which was independent of the sintering temperature.