고온자전반응합성과 확산 열처리를 이용한 FeAl계 금속간화합물 복합판재의 제조

김연욱,윤영목,Kim, Yeon-Wook,Yun, Young-Mok 한국재료학회 2008 한국재료학회지 Vol.18 No.3

Fe-aluminides have the potential to replace many types of stainless steels that are currently used in structural applications. Once commercialized, it is expected that they will be twice as strong as stainless steels with higher corrosion resistance at high temperatures, while their average production cost will be approximately 10% of that of stainless steels. Self-propagating, high-temperature Synthesis (SHS) has been used to produce intermetallic and ceramic compounds from reactions between elemental constituents. The driving force for the SHS is the high thermodynamic stability during the formation of the intermetallic compound. Therefore, the advantages of the SHS method include a higher purity of the products, low energy requirements and the relative simplicity of the process. In this work, a Fe-aluminide intermetallic compound was formed from high-purity elemental Fe and Al foils via a SHS reaction in a hot press. The formation of iron aluminides at the interface between the Fe and Al foil was observed to be controlled by the temperature, pressure and heating rate. Particularly, the heating rate plays the most important role in the formation of the intermetallic compound during the SHS reaction. According to a DSC analysis, a SHS reaction appeared at two different temperatures below and above the metaling point of Al. It was also observed that the SHS reaction temperatures increased as the heating rate increased. A fully dense, well-bonded intermetallic composite sheet with a thickness of $700\;{\mu}m$ was formed by a heat treatment at $665^{\circ}C$ for 15 hours after a SHS reaction of alternatively layered 10 Fe and 9 Al foils. The phases and microstructures of the intermetallic composite sheets were confirmed by EPMA and XRD analyses.

급냉응고에 의한 Mg-5wt%Zn 합금의 결정립 미세화

김연욱,이은종,허보영 ( Yeon Wook Kim,Eun Jong Lee,Bo Young Hur ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.3

N/A In spite of the fact that magnesium has low density and good machinability, its applications are restricted as a structural engineering material because of the poor strength, ductility, and corrosion resistance of the conventional ingot metallurgy alloys. Such properties can be improved by microstructural refinement via rapid solidification processing. In this study, Mg-5wt%Zn alloys have been produced as continuous strips by the melt overflow technique. In order to evaluate the influence of the cooling rate on the grain refinement and mechanical properties, seven different thickness strips were produced by means of controlling the speed of the cooling wheel. Then the microstructual observations were undertaken with the objective of evaluating the grain refinement as function of the cooling rate. The tremendous increase in hardness of Mg-Zn alloy was mainly due to the refinement of the grain structure by the effect of rapid solidification. The formation of intermetallic phases on the grain boundaries may have a positive effect on the corroion resistance. Therefore, despite competition from many other developments, the rapid solidification process emerges as a valuable method to develop superior and commercially acceptable magnesium alloys.

Tripod Polishing을 이용한 불균질 재료의 TEM 시편준비 방법과 미세조직 관찰

김연욱,조명주,Kim, Yeon-Wook,Cho, Myung-Ju 한국현미경학회 2004 Applied microscopy Vol.34 No.2

본 실험에서는 tripod polishing 방법을 이용하여 Pd/GaN/Sapphire 박막, PZT/MgO/Si 박막, 304 stainless steel 분말, $Mo_5Si_3/Mo_2B$ diffusion couple의 매우 다양한 물성이 포함된 불균질 재료의 TEM 시편을 제작하고 분석하였다. Tripod polishing을 사용하여 시편을 준비하면 시편의 종류에 관계없이 시편의 선단부에 매우 광범위한 전자빔 투과 영역을 지닌 TEM 시편을 얻을 수 있었으며, Pd/GaN/Sapphire 박막, PZT/MgO/Si 박막과 같이 기판이 경한 반도체 재료의 경우에는 연마 정도가 균일하며 연마과정 동안 오염이 심하지 않기 때문에 ion milling으로 cleaning 없이 TEM 관찰이 가능하다. 한편 304 stainless steel 분말과 같은 금속재료의 경우 짧은 시간의 ion milling 은 시편의 오염 제거에 도움된다. $Mo_5Si_3/Mo_2B$ diffusion couple에 형성된 실리사이드는 큰 취성 때문에 polishing 동안 시편이 깨지는 현상으로 전자가 투과할 수 있을 정도의 연마가 불가능하여 1시간 정도 ion milling 연마가 필요하다. Tripod polishing으로 TEM 시편을 준비하면 분석하고자 하는 지역을 정확하고도 넓게 연마할 수 있다. 또한 비교적 짧은 시간 내에 ion milling 없이 TEM 시편을 제작할 수 있기 때문에 ion milling에서 유발되는 여러 가지 문제점들을 해결할 수 있는 장점이 있었다. 그러나 tripod polishing은 전부 수작업으로 시편을 준비하기 때문에 시편을 제작하는 과정 동안 매우 세심한 주의가 요구되며 제작자의 숙련도와 경험을 필요로 하는 단점이 있다. The TEM samples prepared by ion milling have the advantage that thin area can be obtained from almost any materials. However, it has the disadvantage that the amount of thin area can often be quite limited. For the cross-sectioned samples and grossly heterogeneous materials, the thickness of less than $0.1{\mu}m$ can be achieved by mechanical grinding and polishing (tripod polisher) and then the TEM samples may be ion-milled for final thinning or cleaning. These approaches were described in this paper. Examples of TEM observations were taken from cross-section samples of thin films on silicon and sapphire, from diffusion layers between $Mo_5Si_3\;and\;Mo_2B$, and from rapidly solidified 304 stainless steel powders embedded in electroplated copper.

인공치근용 CP - Ti 과 Ti 합금의 기계적 성질 및 내식성

김연욱,정종평 ( Yeon Wook Kim,Chong Pyoung Chung ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.5

N/A Commercially pure titanium(cp-Ti) and Ti-15wt%Zr-4wt%Nb-4wt%Ta alloy were melted in vacuum induction furnace. According to the chemical analysis, the content of carbon was above ASTM standard in the cast ingots because of using graphite crucible. The TEM micostructures of cp-Ti and Ti alloy shows that chemically stable TiC precipitates distribute in α-Ti matrix. In order to examine the properties of cp-Ti and Ti-Zr-Nb-Ta alloy for dental applications, mechanical properties and corrosion resistance were investigated. The anodic polarization properties of Ti-Zr-Nb-Zr alloy were almost same as that of cp-Ti in 1% lactic acid. However, as the results of the anodic polarization test in 5% HCl, it was known that Ti-Zr-Nb-Zr alloy showed a rapid decrease in current density at higher potential in comparison with cp-Ti. The yield stress and tensile strengh in Ti-Zr-Nb-Ta were σ_0.2=623 MPa, σ_T.S.=708 MPa and these results showed 30% increase in yield stress in comparison with cp-Ti. (Received August 4, 1998)

급냉응고와 원소첨가에 의한 Mg-Zn 합금의 미세조직 제어

김연욱,허보영 ( Yeon Wook Kim,Bo Young Hur ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.3

N/A Interest in rapid solidification of magnesium alloys stems from the fact that conventional ingot metallurgy alloys exhibit poor strength, ductility, and corrosion resistance. Such properties can be improved by microstructural refinement via rapid solidification processing. In this study, Mg-Zn alloys have been produced as continuous strips by melt overflow technique. In order to evaluate the influence of additional elements on the grain refinement and mechanical properties, Th and Zr were added in rapidly solidified Mg-5wt%Zn alloy. Then the microstructual observations were undertaken with the objective of evaluating the grain refinement as function of the cooling rate and the additional elements. The tremendous increase in hardness of Mg-Zn base alloys was mainly due to the refinement of the grain structure by the effect of rapid solidification and alloying elements. The formation of intermetallic phases on the grain boundaries may have a positive effect on the corroion resistance. Therefore, despite competition from many other developments, the rapid solidification processing of magnesium alloys emerges as a valuable method to develop superior and commercially acceptable magnesium alloys. (Received May 14, 1998)

고온자전합성과 확산 열처리를 이용한 V 이 첨가된 TiAl계 금속간화합물 복합판재의 제조

김연욱,Kim, Yeon-Wook 한국재료학회 2002 한국재료학회지 Vol.12 No.9

The Ti-aluminide intermetallic compound was formed from high purity elemental Ti and Al foils by self-propagating, high-temperature synthesis(SHS) in hot press. formation of $TiAl_3$ at the interface between Ti and Al foils was controlled by temperature, pressure, heating rate, and so on. According to the thermal analysis, it is known in this study that the heating rate is the most important factor to form the intermetallic compound by this SHS reaction. The V layer addition between Al and Ti foils increased SHS reaction temperatures. The fully dense, well-boned inter-metallic composite($TiA1/Ti_3$Al) sheets of 700 m thickness were formed by heat treatment at $1000^{\circ}C$ for 10 hours after the SHS reaction of alternatively layered 10 Ti and 9 Al foils with the V coating layer. The phases and microstructures of intermetallic composite sheets were confirmed by EPMA and XRD.

기술자료 : EPMA 분석법

김연욱 ( Yeon Wook Kim ) 한국주조공학회 2003 한국주조공학회지 Vol.23 No.1

비귀금속 치과용 합금의 주조성과 기계적 특성

김연욱 ( Yeon Wook Kim ) 한국주조공학회 2007 한국주조공학회지 Vol.27 No.4

HP-JK 기반의 자율주행 기법

김연욱 ( Yeon Wook Kim ),박성훈 ( Seong Hun Park ),전다빈 ( Da Bin Jun ),한창현 ( Chang Hyun Han ),최재성 ( Jaesung Choi ) 한국정보처리학회 2017 한국정보처리학회 학술대회논문집 Vol.24 No.2

Using a small computer called Raspberry Pie, the webcam is interlocked with the webcam to detect the desired color using hsv and find the representative line using the hough transform in the detected color. Another new line is extracted and the coordinates where the lines meet are called the vanishing point and we want to make a system that autonomously travels through the vanishing point.

농작업용 보완대체의사소통 앱을 위한 통신 및 그림 메시지 표현 연구

김연욱(Yeon Wook Kim),김태원(Tae Won Kim),조우형(Woo Hyeong Cho),이상민(Sangmin Lee) 한국재활복지공학회 2021 한국재활복지공학회 학술대회논문집 Vol.2021 No.4