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김형석,전채홍,송권,권숙인 ( Hyung Seok Kim,C . H . Jeon,Gun Song,S . I . Kwun ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.1
Pure copper is widely used for base material for electrical and electronic parts because of its good electrical conductivity. However, it has such a low strength that various alloying elements are added to copper to increase its strength. Nevertheless, alloying elements which exist as solid solution elements in copper matrix severely reduce the electrical conductivity. The reduction of electrical conductivity can be minimized and the strengthening can be maximized by TMT(Thermo-Mechanical Treatment) in copper alloys. In this research, the effects of TMT on mechanical and electrical properties of Cu-Ni-Al-Si-P, Cu-Ni-Al-Si-P-Zr and Cu-Ni-Si-P-Ti alloys aged at various temperatures were investigated. The Cu alloy with Ti showed the hardness of Hv 225, electrical conductivity of 59.8%IACS, tensile strength of 572MPa and elongation of 6.4%.
Al-Mg합금의 압연변수에 다른 미세구조의 변화와 고온인장특성
김태규,전채홍,권숙인,박종우 ( Tae Kue Kim,C . H . Jeon,S . I . Kwun,Jong Woo Park ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.2
The effect of alloying elements, precipitate size, its distribution, and dislocation substructure resulted from warm rolling or cold rolling in the superplastic Al-Mg alloy system was investigated. One of the major requirements for fine structure superplasticity is that the grain size should be very small. Fine grain structure is controlled by the dislocation substructure and the dynamic recrystallization during hot or warm working. The recovery of Al-Mg base alloys was constrained resulting in relatively high dislocation density when the alloys were warm rolled. In particular, Al-Mg-Zr alloy exhibited the smallest sub-grain size among Al-Mg alloys containing Mn, Cu, Zr as a third element. The Al-Mg-Mn alloy cold rolled 80% after hot rolling showed the maximun strain rate sensitivity exponent, m, of 0.75 under strain rate of 7.1×10^(-4)/s at 500℃. The elongation of the alloys was limited in spite of high m values due to large dispersoids containing appreciable amount of Fe impurities.
수퍼 2상 스테인리스강의 열처리 조건변화에 따른 첨가원소 질소의 거동
김형석,전채홍,송권,권숙인 ( Hyung Seok Kim,C . H . Jeon,Gun Song,S . I . Kwun ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.1
After changing the heat treating atmosphere of nitrogen gas, argon gas and vacuum, the nitrogen contents, microstructural changes, hardness and corrosion resistance of 0.25wt.%N alloyed super duplex stainless steel have been investigated in the temperature range from 1050℃ to 1350℃. The nitrogen content showed to be increased up to 0.36wt.% after heat treating the specimen in nitrogen gas at 1200℃, while the decrement of nitrogen content in vacuum atmosphere was shown down to 0.03wt.% at 1350℃. After heat treating in the mixed gas atmosphere of argon and nitrogen at 1250℃, the surface γ phase existed as α+γ phase increased with increasing nitrogen gas content. The γ single phase appeared at the surface above 80%N₂gas, while the surface α single phase was shown below 20%N₂gas. When heat treating the specimen in nitrogen gas at 1050℃, the hardness of austenite phases increased above Hv 40 at the surface layer compared to the hardness of the core parts, while decrement of denitriding effect caused to the hardness nearly unchanged between surface and the core parts after heat treating in vacuum atmosphere. The surface γ single phase specimen showed superior corrosion resistance than the surface α single phase specimen. The surface α phase existed in the α+γ microstructure showed higher corrosion resistance after heat treating in the nitrogen gas atmosphere than the a phase heat treated in the argon gas and vacuum atmosphere.
김용환(Y. H. Kim),송진헌(J. H. Song),권숙인(S. I. Kwon),전채홍(C. H. Jeon),박기성(K. S. Park),김승태(S. T. Kim) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8
High temperature brazing with nickel-based filler metal was carried out to study the high temperatuer brazing behavior of superalloys. Both additive metal(IN 738) and the filler metals(AMDRY DF-4B and AMS 4778) were provided in a from of mixed with gas atomized powders and organic binder. This brazing paste was inserted into the gap between the joining parts, and a pressure of 0.05 to IMPa was applied to joining parts. The brazing process was conducted in vacuum furnace under2×10??torr. The microstructure and porosity of the brazed area were characterised by SEM, EDX and image analyser. The Cr borides with a blocky morphology were presents in the matal braged with DF-4B filler metals. Ni-Ni₃B eutectic phase was observed in both filler metals. The area braged with DF 4B exhibited much higher porosity than the one with AMS 4778. the pressure of 0.1-0.4MPa was found to produce lower porosity.
신명철,권숙인,전채홍 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.2
The fractal geometry is a non-Euclidean geometry which describes the naturally irregular or fragmented shapes, so that it can be applied to fracture surface of a material to investigate the fracture process. The fractal dimension of irregular surface has fractal values ranging from 2 to 3, and that of irregular line profile has fractal values ranging from 1 to 2. In this investigation, this fractal geometry was appiled to the fracture surface of Al-Li alloy in order to correlate the fracture phenomena to microstructures of this alloy. Vertical section fracture profile methods were used to determine the fractal dimension, D_F. We found a correlation between fractal dimension and toughness of the alloy. More specifically, the logarithm values of toughness increased with those of (D_F-1), but not linearly when arbitrary lengths of measuring unit were used to depict the fracture line profile. However, a very good linear correlation was observed when the length of measuring unit was chosen such that its magnitude is of microstructural size. The microstructures affecting fracture processes were found to be grain size, slip step and fibering size in Al-Li alloy.