Papers by Author: Chang Hee Lee

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Authors: In Chul Lim, Cheul Muu Sim, Byung Hyun Lee, S.Y. Hwang, B.J. Jun, Chang Hee Lee
Authors: In Chul Lim, B.C. Lee, Cheul Muu Sim, Moon Saeng Kim, Chang Hee Lee, B.J. Jun, H. Kobayashi, Shigeya Watanabe, Masanori Satoh
Authors: Seung Wook Lee, Joon Cheol Kim, Cheul Muu Sim, Kwang Pyo Hong, Jong Kyu Cheon, Chang Hee Lee, Young Jin Kim
Authors: Young Sup Lee, Cheol Ho Lim, C.H. Lee, K.W. Seo, Seung Y. Shin, Chang Hee Lee
Abstract: In this study, a diffusion bonding of aluminium alloy A6061 was preformed using an Ag-28Cu filler metal in order to conduct eutectic brazing. Melting mechanism was surveyed. Interface behaviors of the brazed joints were observed after brazing and T6 solution treatment. Also, tensile property of the brazed joints was examined. During diffusion bonding of Al6061 alloys with Ag-28Cu filler metal, eutectic melts were formed by eutectic reaction between Al6061 and Ag-28Cu filler metal. It was found that the reaction layer consist of two phases formed at the interface between AA6061 and Ag-28Cu filler metal. EPMA analysis revealed that two phases in the reaction layers consist of Ag-rich phase and Cu-rich phase. Tensile strength was 300 MPa after ageing treatment at 175°C.
Authors: Sang Jin Cho, Chang Hee Lee, Y.J. Kim, Myung Kook Moon, Thomas Krist
Authors: Chung Hyo Lee, Young Sup Lee, Dong Choul Cho, Chang Hee Lee
Abstract: The process of Direct Bonding Copper (DBC) is performed by a spinel reaction between CuO and Al2O3. In order to develop DBC on alumina substrate with high bonding strength, alumina substrate was preformed as follows: Cu was sputter-deposited on alumina substrate. Sputter-Deposited Cu (SDC) on alumina substrate was oxidized at 673K for 30min in air atmosphere and then stabilized at 1273K for 30min in N2 gas atmosphere to improve bonding strtrength between preformed alumina substrate and SDC layer. Subsequently, the Cu-foil (300µm) was bonded on preformed-alumina substrate in N2 gas atmosphere at 1342~1345K. It was found that optimum condition of DBC on preformed-alumina substrate could be successfully obtained at 1345K for 30min. Consequently, bonding strength of DBC on alumina substrate was the high value of 80N/cm. Observation and analysis of microstructure for Cu sputtered DBC showed that reaction compounds such as CuAlO2 and CuAl2O4 approved to be formed in the vicinity of interface between Cu and alumina substrate.
Authors: Seok Hoon Kim, Myung Kook Moon, Chang Hee Lee, Vyacheslav T. Em, Young Hyun Choi, Sang Jin Cho, Kwang Pyo Hong, Young Jin Kim, Uk Won Nam, Kyung Nam Kong
Authors: Young Soo Han, Baek Seok Seong, Chang Hee Lee, Geun Hee Lee, Chang Kyu Rhee, Wheung Whoe Kim
Authors: Young Soo Han, Eun Joo Shin, Baek Seok Seong, Chang Hee Lee, Duck Gun Park
Abstract: The irradiation induced defects of irradiated reactor pressure vessel(RPV) steel were investigated by a small angle neutron scattering. The degradation of the mechanical properties of RPV steels during an irradiation in a nuclear power plant is closely related to the irradiation induced defects. The size of these defects is known to be a few nanometers, and the small angle neutron scattering technique is regarded as the best non destructive technique to characterize the nano sized inhomogeneities in bulk samples. The RPV steel was irradiated in the HANARO reactor in KAERI. The small angle neutron scattering experiments were performed at SANS instrument in the HANARO reactor. Both unirradiated and irradiated RPV steels were measured and the SANS data of both steels were compared. The nano sized irradiation induced defects were quantitatively analyzed by SANS. The type of defects was also analyzed based on the SANS results, and the effect of the chemical composition of the RPV steel on the irradiation induced defects was discussed.
Authors: Eun Joo Shin, Baek Seok Seong, Tae Won Joung, Kwang Pyo Hong, Chang Hee Lee, Young Jin Kim
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