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- 저자 : 현창용 ( C. Y. Hyun ) (검색결과 6 건)
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전기방전소결에 의해 제조된 다공성 및 다공성 표면을 갖는 Ti-6Al-4V 임플란트 : (2) 경도 및 압축강도
현창용,허재근,이원희,Hyun, C. Y.,Huh, J. K.,Lee, W. H. 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.5
Porous and porous surfaced Ti-6Al-4V implant compacts were fabricated by electro-discharge-sintering (EDS) of atomized spherical Ti-6Al-4V powders with a diameter of $100-150\;{\mu}m$, The solid core formed in the center of the compact after discharge was composed of acicular ${\alpha}+{\beta}$ Widmanstatten grains, The hardness value at the solid core was much higher than that at the particle interface or particles in the porous layer, which can be attributed to both heat treatment and work hardening effects induced from EDS, The compressive yield strength was in a range of 19 to 436 MPa which significantly depends on both input energy and capacitance, Selected porous-surfaced Ti-6Al-4V implant compacts with a solid core have much higher compressive strengths compared to the human teeth and sintered Ti dental implants.
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저진공 분위기 전기방전소결에 의해 제조된 다공성 Ti-6Al-4V 임플란트의 표면특성 연구
현창용,허재근,이원희,Hyun, C.Y.,Huh, J.K.,Lee, W.H. 한국재료학회 2006 한국재료학회지 Vol.16 No.3
A single electro-discharge-sintering (EDS) pulse (1.0 kJ/0.7 g), from a $300{\mu}F$ capacitor, was applied to atomized spherical Ti-6Al-4V powder in a low vacuum to produce porous-surfaced implant compacts. A solid core surrounded by a porous layer was formed by a discharge in the middle of the compact. XPS (X-ray photoelectron spectroscopy) was used to study the surface characteristics of the implant material. C, O, and Ti were the main constituents, with smaller amounts of Al, V, and N. The implant surface was lightly oxidized and was primarily in the form of $TiO_2$ with a small amount of metallic Ti. A lightly etched EDS implant sample showed the surface form of metallic Ti, indicating that EDS breaks down the oxide film of the as-received Ti-6Al-4V powder during the discharge process. The EDS Ti-6Al-4V implant surface also contained small amounts of aluminum oxide in addition to $TiO_2$. However, V detected in the EDS Ti-6Al-4V implant surface, did not contribute to the formation of the oxide film..
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전기방전소결에 의해 제조된 다공성 및 다공성 표면을 갖는 Ti-6Al-4V 임플란트 : (1) 제조방법 및 기본적 특성
현창용,허재근,이원희,Hyun, C. Y.,Huh, J. K.,Lee, W. H. 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.5
Implant prototypes with various porosities were fabricated by electro-discharge-sintering of atomized spherical Ti-6Al-4V powders. Single pulse of 0.75 to 2.0 kJ/0.7 g-powder, using 150, 300, and $450{\mu}F$ capacitors was applied to produce a fully porous and porous surfaced implant compact. The solid core formed in the center of the compact after discharge was composed of acicular ${\alpha}+{\beta}$ grains and porous layer consisted of particles connected in three dimensions by necks. The solid core and neck sizes increased with an increase in input energy and capacitance. On the other hand, pore volume decreased with increased capacitance and input energy due to the formation of solid core. Capacitance and input energy are the only controllable discharge parameters even though the heat generated during a discharge is the unique parameter that determines the porosity of compact. It is known that electro-discharge-sintering of spherical Ti-6Al-4V powders can efficiently produce fully-porous and porous surfaced Ti-6Al-4V implants with various porosities in a short time less then 400 isec by manipulating the discharging condition such as input energy and capacitance including powder size.
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전기방전소결에 의해 제조된 다공성 Titanium 임플란트의 기계적 특성
현창용,허재근,이원희,Hyun, C.Y.,Huh, J.K.,Lee, W.H. 한국재료학회 2006 한국재료학회지 Vol.16 No.3
Porous surfaced Ti implant compacts were fabricated by electro-discharging-sintering (EDS) of atomized spherical Ti powders. Powders of $50-100{\mu}m$ in diameter were vibratarily settled into a quarts tube and subject to a high voltage and high density current pulse in Ar atmosphere. Single pulse of 0.7 to 2.0 kJ/0.7 gpowder, from 150, 300, and $450{\mu}F$ capacitors was applied in less than $400{\mu}sec$ to produce twelve different porous-surfaced Ti implant compacts. The solid core formed in the center of the compact shows similar microstructure of cp Ti which was annealed and quenched in water. Hardness value at the solid core was much higher than that at the particle interface and particles in the porous layer, which can be attributed to both heat treatment and work hardening effects induced by EDS. Compression tests were made to evaluate the mechanical properties of the EDS compacts. The compressive yield strength was in a range of 12 to 304MPa which significantly depends on input energy. Selected porous-surfaced Ti-6Al-4V dental implant compacts with a solid core have much higher compressive strengths compared to the human teeth and sintered Ti dental implants fabricated by conventional sintering process.
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초음파 속도 측정에 의한 주철의 미세구조 및 품질평가 가능성 검토
최찬양(C. Y. Choi),현창용(C. Y. Hyun),변재원(Jai-Won Byeon) 한국비파괴검사학회 2012 한국비파괴검사학회지 Vol.32 No.2
초음파 속도를 이용하여 다양한 종류의 주철에 대해 미세구조와 품질 특성을 평가하였다. 상용으로 사용되는 3종의 회주철 및 3종의 구상흑연주철을 준비하였으며, 열처리 미세구조의 영향을 평가하기 위해 구상흑연주철을 어닐링 열처리를 다르게 하여 시편을 준비하였다. 초음파 전파 속도 측정, 미세구조(펄라이트 분율, 흑연의 길이 및 구상화율) 정량화, 경도 측정을 행하여 이들 파라미터 사이의 경험적 상관관계를 확인하였다. 구상흑연주철의 초음파 전파 속도가 회주철에서의 속도보다 크게 나타났다. 구상흑연주철에서 펄라이트 미세조직의 분율이 감소할수록 경도 및 초음파 속도는 감소하였다. 초음파 속도를 주철 소재의 품질관리를 위한 비파괴평가 파라미터로서 사용할 수 있는 가능성을 보여주었다. It was attempted to evaluate the microstructure and quality of various types of cast iron by ultrasonic velocity measurement. Three types of commercial gray cast iron and ductile cast iron were used for this investigation, respectively. One type of the ductile cast iron was heat-treated as a function of annealing time to produce different microstructure. Ultrasonic velocity measurement, microstructural analysis (pearlite area fraction, graphite length and nodularity), and hardness measurement were performed to find empirical correlations among these parameters. Ultrasonic velocity of ductile cast iron was markedly faster than that of gray cast iron. Ultrasonic velocity decreased with the decrease of fraction of pearlite structure. As a quality monitoring parameter of cast iron, potential of ultrasonic velocity was suggested.
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ECAP 강가공에 의한 마그네슘 AZ31합금의 결정립 미세화 및 미세조직 불안정성
김호경 ( H. K. Kim ),정강 ( K. Chung ),현창용 ( C. Y. Hyun ) 한국열처리공학회 2004 熱處理工學會誌 Vol.17 No.3
N/A Equal channel angular pressing (ECAP) technique had been adapted to the Mg alloy (AZ31) for achieving effective grain refinement through severe deformation. The average grain size of 2.5 ㎛ could be obtained after 4 passes. The stability of the ECAPed structure at elevated temperatures was examined by annealing the ECAPed materials over a wide range of temperature between 473 and 748 K. The average activation energy, Q, for static grain growth of 1, 2 and 3 passes was 33.7 kJ/㏖ (=0.25QL, activation for lattice diffusion). The abnormally low Q value in the lower temperature range may indicate that grain growth occurs in the unrecrystallized microstructure where non-equilibrium grain boundaries containing a large number of extrinsic dislocations exist. The yield stresses of the ECAPed alloys decreased whereas the elongations increased after the ECAP process. These results should be related to the modification of texture for easier slip on basal plane.
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