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용탕단조한 미세강선 보강 알루미늄 복합재료의 미세조직에 대한 고찰
정봉용,이인우,박흥일,김준수,김명호 ( Bong Yong Jeong,In Woo Lee,Heung Il Park,Jun Su Kim,Myung Ho Kim ) 한국주조공학회 1994 한국주조공학회지 Vol.14 No.5
N/A Aluminum matrix composites reinforced by fine steel wires were fabricated by squeeze casting process. Preforms made of fine steel wires were prepared with different surface conditions, namely uncoated(TN), carbo-nitriding treated(TT), and brass coated(TA). Squeeze casting were performed under the pressure of 1500㎏/㎠ for 3min. during solidification, and pouring temp. of the melt being 750℃ and the steel mold being preheated at 250℃. Microstructural characteristics were evaluated, particularly concerned with the effect of the surface conditions of the preforms. The results obtained from this study are like these. TN specimens show partially non-wetted regions, due to easy formation of oxides on the surface of the fine steel wires. TT specimens show no interfacial reaction between the steel wires and the aluminum alloy matrix, possibly due to the formation of carbo-nitrided zone on the surface of the steel wires. TA specimens show excellent wettabillity between the reinforced steel wires and the aluminum alloy matrix and very thin interfacial zone is formed between them. During the solution hardening treatment of TA specimens, thickness of the interfacial reaction zones were increased with the solution treating time. TA specimens show typical ductile fracture in tensile test, but TT specimens show brittle fracture possibly due to the formation of the brittle hard surface on the steel wires during carbo-nitriding treatments. TA specimens which were reinforced with 40 vol.% of the fine steel wires exhibit high tensile strength of 77.l㎏f/㎟ and impact value of 8.l㎏f-m/㎠.
Cu-Ag 합금의 전기전도도와 기계적 특성에 미치는 P , Mg 의 영향
정봉용,김기태,정운재,김명호 ( Bong Yong Jeong,Ki Tae Kim,Woon Jae Jung,Myung Ho Kim ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.2
N/A Effects of P and Mg on the electrical conductivity and mechanical properties of Cu-Ag alloys were investigated experimentally. Small addition of these alloying elements decreased the electrical conductivity of Cu alloy greatly, especially for P addition. The maximum amounts of P addition to obtain the electrical conductivity being over 90%IACS was found to be about 0.019wt.%, and in this case recrystallization temperature of the addition was about 450˚C. The tensile strength was not changed significantly by the addition of P. However, for Cu-Ag-P-Mg alloys, P-Mg compound was precipitated by heat treatment at 450˚C for 1 hour. Such a precipitation of P-Mg compound increased the electrical conductivity of the alloy from 47~57%IACS to 72.3~86.6%IACS. (Received January 15, 1998)
시효 열처리에 따른 Cu-Be 합금의 전기,기계적 특성 고찰
류민 ( Min Ryou ),이병수 ( Byoung Soo Lee ),정봉용 ( Bong Yong Jeong ),김명호 ( Myung Ho Kim ) 한국주조공학회 2011 한국주조공학회지 Vol.31 No.6
The influence of aging treatment on the microstructure, mechanical and electrical properties of Cu-Be alloy for connector material applications was investigated. The properties of mechanical strength and electrical conductivity were found to increase with increasing aging temperature. By the way, SEM/EDS and TEM analysis exhibited that beryllides precipitation (CoBe and NiBe) with a size of 50 nm were distributed in grains. It was, therefore concluded that these beryllide precipitates improved the mechanical strength and also it was favor in increasing of electrical conductivity.
강의 플라즈마 질화시 OES 를 이용한 활성종 및 질화층 생성거동에 관한 연구
김명호,정봉용 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.12
In order to characterize the behavior of active species during the pulse plasma nitriding process, OES(optical emission spectroscopy) measurements were performed for various gas compositions, treatment temperatures, duty factors ratios and different gas pressures in the reactor. Results of the OES measurements were compared to those of the metallurgical analysis of plasma nitrided sintered steel and high speed steel substrates. It was found that the spectral intensities of N^+₂ and N₂ were influenced by treatment parameters and the thickness of nitride layer and size of micro-pore increased with increasing the temperature and pulse ratio. Especially, the compound layer was mainly influenced by gas pressure.
김명호,이정근,정봉용 한국주조공학회 1999 한국주조공학회지 Vol.19 No.4
Effects of Ca on the deoxidation and properties of pure copper were investigated by means of optical and scanning electron microscopy, nitrogen-oxygen analyzer, centurion NDT digital conductivity meter, hardness and tensile measurement. Addition of Ca in pure copper melt contained 0.036% oxygen decreased markedly oxygen content to 0.005%, and high electrical conductivity over 96% IACS was also maintained. Thus, for the production of high conductivity copper, Ca has been shown to be proper deoxidant. Softening temperature and tensile property of copper were decreased slightly due to formation of Ca-phases with addition of 0.3% Ca. It was concluded that proper amount of Ca addition for deoxidation of pure copper was about 0.05∼0.10% to obtain high conductivity and properties. (Received June 30, 1999)
펄스 플라즈마 질화처리된 소결강의 특성에 미치는 공정변수의 영향
김명호,정봉용,정구환 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.10
Sintered Fe-4 wt.%Ni-1.5 wt.%Cu-0.5 wt.%Mo steels were purse plasma nitrided and the influence of nitriding treatment conditions(temperature, gas mixture, pulse ratio) on the surface layer microstructure the micropore formation behavior and the compound layer properties of the steel has been studied. The pulse ratio was varied from 0.1 to 1, and the temperature and gas ratio(N₂:H₂) were varied from 500℃ to 570℃ and 4:1, 1:1, 1:4, respectively. The number and size of micropore in the compound layer were decreased in a pulsed DC glow discharge by reducing the plasma power and the partial pressure of nitrogen gas. The cross-sectional WDX analysis showed that the penetration depth of nitrogen in sintered steed was 3 times thicker than that of bulk material.
SCM 440 의 마이크로 펄스 플라즈마 질화처리시 펄스비 변화에 따른 질화층 특성변화
김명호,정봉용,정구환 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.2
The aim of this work is to develop the understanding of micro-pulsed plasma nitriding from the microstructural observations. In order to examine the difference of micro-pulsed plasma nitriding, pulse ratio was varied ranges from 0.1 to 1 by controlling both the pulse duration time and the pulse repetition time. Properties of the nitrified layer were analysed by using optical microscope, scanning electron microscope(SEM), atomic force microscope(AFM), X-ray diffractometer(XRD) and micro-vickers hardness tester. It was found that both the compound layer thickness and the case depth decreased with decreasing of pulse ratios and surface roughness also decreased with decreasing of pulse ratios.
주철의 플라즈마 산화처리시 표면특성 및 흑연에칭거동에 미치는 duty factor 의 영향
김명호,정봉용 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.11
The influence of pulsed-dc plasma oxidation and nitriding treatment on the surface microstructure with variation of duty factors of cast iron is studied. The phase compositions of the layers were evaluated by using X-ray diffraction. OES(Optical Emission Spectroscopy) have been applied to analyse the active species during plasma oxidation. Surface properties of plasma oxidation and nitriding treated specimens were summarized. Oxide composition was not changed with duty factor (0.1∼0.9, pulse on-off time : 100∼900 ㎲, pulse frequency 1,000 Hz), but the retained α-Fe reduced significantly with increasing duty factor. The intensity ratio of oxygen plasma spectra shows that the formation density of oxygen radical reached maximum at duty factor of 0.5 and etching depth was 1,840 ㎚ under that condition.
김명호,정봉용 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.8
Ductile cast iron was treated with the so-called duplex surface treatment process, which is a combined plasma nitriding and oxidation process. The surface and cross-sectional microstructures and corrosion characteristics were analyzed. Potentiodynamic polarization curves were obtained at room temperature from the samples immersed in 3% NaCl solution. In case of the oxidation after nitriding, oxide layer(double layers of Fe₂O₃ and Fe₃O₄was found to be formed on the top of the compound layer(γ'- Fe₄N). The value of the measured parameter Ra(roughness average) of plasma nitrided sample was higher than that of plasma oxidation treated sample. The untreated sample showed typical graphitic corrosion, and the plasma treatment was found to increase the corrosion resistance.