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MA법으로 제조된 Ni기 합금에서 Y<sub>2</sub>O<sub>3</sub> 첨가에 따른 인장강도변화와 시효처리 효과
김일호,이원식,고세현,장진만,권숙인,Kim, Il-Ho,Lee, Won-Sik,Ko, Se-Hyun,Jang, Jin-Man,Kwun, Sook-In 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.1
Ni-20Cr-20Fe-5Nb alloy with or without $Y_2O_3$ was manufactured by mechanical alloying process and consolidated by spark plasma sintering (SPS). The grain size of the alloy with $Y_2O_3$ was smaller than that of alloy without $Y_2O_3$ which results from the effect of $Y_2O_3$ suppressing grain growth. The tensile strength at room temperature was increased by the addition of $Y_2O_3$ but decreased abruptly at temperature above $600^{\circ}C$. It seems to result from the change of deformation mechanism due to fine grain size, that is, grain boundary sliding is predominant at above $600^{\circ}C$ while internal dislocation movement is predominant at below $600^{\circ}C$. After conventional heat treatment process of solution treatment and aging, a small amount of ${\delta}(Ni_3Nb)$ phase was formed in Ni-20Cr-20Fe-5Nb alloy while a large amount of ${\gamma}"(Ni_3Nb)$ was formed in Inconel 718 in the previous report. This is due to exhaustion of Nb content by the formation of NbC during consolidation.
무전해 도금을 이용한 AlN/Cu 복합재료 제조와 AlN 입자크기에 따른 복합재의 열특성 평가
조성철 ( Sung Chul Cho ),고세현 ( Se Hyun Ko ),김혜성 ( Hye Sung Kim ),안재평 ( Jae Pyung Ahn ),한준현 ( Jun Hyun Han ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.12
AlN/Cu composite powders with a core-shell structure were synthesized by a new technique using electroless plating of Cu on AlN particles and consolidated by spark plasma sintering (SPS). Dependence of the thermal conductivity and coefficient of thermal expansion (CTE) of the AlN/Cu composites on the particle size of AlN were studied. The thermal conductivity and coefficient of thermal expansion were significantly dependent on the existence of both boundary pores surrounding the Cu-coated AlN particles and the internal pores of the AlN particles. In order to eliminate the pores, the temperature and pressure of SPS were increased and the AlN particles were heat-treated at high temperature. Adoption of the core-shell AlN/Cu composite powders facilitated the fabrication of AlN/Cu composites with low porosity and uniform distribution in the AlN in Cu matrix.
마이크로PIM용Fe마이크로-나노복합분말피드스톡제조시혼합거동과미세구조변화
이원식 ( Won Sik Lee ),이재성 ( Jai Sung Lee ),고세현 ( Se Hyun Ko ),유우경 ( Woo Kyung You ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.7
The present investigation has been performed on the mixing behavior and microstructural development during fabrication of Fe micro-nano powder feedstock for a micro-powder injection molding process. The mixing experiment using a screw type blender system was conducted to measure the variations of torque and temperature during mixing of Fe powder-binder feedstock with progressive powder loading for various nano-powder compositions up to 25%. It was found that the torque and the temperature required in the mixing of feedstock increased proportionally with increasing cumulative powder loading. Such an increment was larger in the feedstock containing higher content of nano-powder at the same powder loading condition. However, the maximum value was obtained at the nano-powder composition of not 25% but 10%. It was owing to the 'roller bearing effect' of agglomerate type nano-powder acting as lubricant during mixing, consequently leading to the rearrangement of micro-nano powder in the feedstock. It is concluded that the improvement of packing density by rearrangement of nano-powders into interstices of micro-powders is responsible for the maximum powder loading of about 71 vol.% in the nano-powder composition of 25%.
신제식 ( Je Sik Shin ),김기태 ( Ki Tae Kim ),고세현 ( Se Hyun Ko ),안동진 ( Dong Jin An ),김명호 ( Myung Ho Kim ) 한국주조공학회 2013 한국주조공학회지 Vol.33 No.1
In order to develop an aluminum alloy, that can combine high thermal conductivity and good castability and anodizability, aluminum alloys with low Si content, such as Al-(0.5~1.5)Mg-1Fe-0.5Si and Al-(1.0~1.5)Si-1Fe-1Zn, were designed. The developed aluminum alloys exhibited 170~190% thermal conductivity (160~180 W/mK), 60~85% fluidity, and equal or higher ultimate tensile strength compared with those of the ADC12 alloy. In each developed alloy system, the thermal conductivity decreased and the strength increased with the increment of Mg and Si, which are the significant alloying elements. The fluidity was in reverse proportion to the Mg content and in proportion to the Si content. The Al-(0.5~1.5)Mg-1Fe-0.5Si alloys exhibited better fluidity in thick-wall castings, while the Al-(1.0~1.5)Si-1Fe-1Zn alloys were better in thin-wall castability due to their lower surface energies. The fluidity behavior was complexly affected by the heat release for the solidification, viscosity, solidification range, and the type, quantity, and formation juncture of the main secondary phase.
다이캐스팅용 고열전도도 Al-Zn-Mg-Fe 합금의 특성에 미치는 Zn 및 Mg 첨가량의 영향
김기태 ( Ki Tae Kim ),임영석 ( Young Suk Lim ),신제식 ( Je Sik Shin ),고세현 ( Se Hyun Ko ),김정민 ( Jeong Min Kim ) 한국주조공학회 2013 한국주조공학회지 Vol.33 No.3
The effects of Zn and Mg amounts on the solidification characteristics, microstructure, thermal conductivity and tensile strength of Al-Zn-Mg-Fe alloys were investigated for the development of high thermal conductivity aluminium alloys for die casting. Zn and Mg amounts in Al-Zn-Mg-Fe alloys had a little effect on the liquidus / solidus temperature, the latent heat for solidification and the fluidity of Al-Zn-Mg-Fe alloys. Thermo-physical modelling of Al-Zn-Mg-Fe alloys by JMatPro program showed MgZn2, AlCuMgZn and Al3Fe phases on microstructure of their alloys. Increase of Zn and Mg amounts in Al-Zn-Mg-Fe alloys resulted in gradual reduction of the thermal conductivity of their alloys. Increase of Mg amounts in Al-2%Zn-Mg-Fe alloys had little effect on the tensile strength of their alloys, but increase of Mg amounts in Al-4%Zn-Mg-Fe alloys resulted in steep increase of the tensile strength of their alloys.
In-Mold Rheology 평가를 통한 분말사출성형공정 최적화
장진만(Jin Man Jang),차범하(Bermha Cha),서정식(Jungsik Seo),고세현(Se-Hyun Ko),손성호(Seong Ho Son),이원식(Wonsik Lee),나영상(Young-Sang Na) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
두 종류의 피드스톡과 몰드를 이용하여 각각의 몰드에 대한 In-mold Rheology 곡선을 산출하였으며, 이를 통해 rheology거동을 변화시키는 요인에는 피드스톡의 물리적 특성(점도) 뿐 아니라 몰드의 형상 및 크기 또한 포함이 됨을 확인하였다. Rheology평가를 통해 설정된 최적의 사출속도가 사출 성형체와 소결체에 미치는 영향을 관찰한 결과 전체적인 형상 및 크기는 유사하게 나타나는 반면 가장자리 부분의 예리함과 조직의 차이를 나타내었다.
차범하(Bermha Cha),장진만(Jin Man Jang),서정식(Jungsik Seo),고세현(Se-Hyun Ko),손성호(Seong Ho Son),이원식(Wonsik Lee),유우경(Woo Kyung You),이재성(Jai-Sung Lee) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
재활용된 티타늄 수소화물 분말을 사용하여 피드스톡을 제조하고, 이를 이용하여 사출성형공정 조건을 최적화 하였다. 원료분말은 Ti chip의 재활용 공정을 통해 제조된 평균 350nm 크기의 분말을 사용하였으며, 피드스톡 제조 시 최적 분말 고상율은 68%였다. 제조된 피드스톡은 2000Pa.s 이하의 점도를 나타냈으며, 최적의 사출조건으로 미세한 부분까지 건전하게 성형된 사출체를 제조하였다. 또한 피드스톡의 열분석 결과를 이용하여 탈지 및 탈수소화 공정의 최적화를 이루었으며, 고진공하에서 소결 시 완전치밀화를 얻을 수 있었다.
Al-2Zn-0.2Fe-xMg 합금의 물성 및 주조특성에 미치는 Mg함량의 영향
김정민 ( Jeong Min Kim ),박준식 ( Joon Sik Park ),김기태 ( Ki Tae Kim ),고세현 ( Se Hyun Ko ) 한국주조공학회 2012 한국주조공학회지 Vol.32 No.2
Aluminium-silicon based casting alloys have received an attention for high electrical and thermal conductivity applications, however relatively low conductivity of Al-Si alloys often limits the application. Efforts have been made to develop new high conductivity aluminium casting alloys containing no or less silicon. In this study Al-Zn-Fe based alloys were selected as the new alloys, and the effect of Mg additions on their properties and casting characteristics were investigated. As the magnesium content was increased, the tensile strength of Al-2Zn-0.2Fe based alloy was remarkably increased, while the electrical conductivity was deteriorated. It was observed that the fluidity of the alloys was generally inversely proportional to the Mg content but the hot cracking resistance was rather proportional to it. Cooling curve analyses were carried out to measure the actual solidification range and dendrite coherency temperature.