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Al-Li-Cu-Mg합금의 조직과 기계적 성질에 미치는 가공열처리의 영향
우기도,조현기 ( Kee Do Woo,Hyun Kee Cho ) 한국열처리공학회 1990 熱處理工學會誌 Vol.3 No.1
Effects of thermomechanical treatments(TMT) on the microstructures and mechanical properties in Al-2.27%, Li-1.28%, Cu-0.63%, Mg-0.12%, Zr alloy were investigated. The TMT process improved the tensile strength. Growth of δ`, S` and T₁phases was restrained by TMT processes while the density of δ`, S` and T₁phases was increased by TMT processes. The TMT treated specimens tend to fail in inter-subboundary mode. The increases of strength by the T-HA processes were compared to those of the T-AHA processes.
Sc을 첨가한 Al-7.7wt%Zn-2.0wt%Mg-1.9wt%Cu합금의 고온 변형거동
우기도,유용석,김석원,Woo, Kee-Do,Ryu, Yong-Seok,Kim, Sug-Won,Deliang Zhang 한국재료학회 2003 한국재료학회지 Vol.13 No.12
The Al-7.7Zn-2.0Mg-1.9Cu-0.1Zr-0.1Sc alloy exhibited excellent elongation by the new thermomechanical treatment (TMT) process; solution treatment and furnace cooling\longrightarrowhot and cold rolling and then annealing for short time. Tensile test at high temperature from 430 to $500^{\circ}C$ has been performed with various strain rates using for the Al-7.7Zn-2.0Mg-1.9Cu-0.1Zr-0.1Sc alloy obtained by the TMT process. The elongation of the Al-7.7Zn-2.0Mg-1.9Cu-0.1Zr-0.1Sc was 550% tensile tested at $470^{\circ}C$ temperature and 2.2 $\times$ $10^{-3}$ $s^{-1}$ strain rate. The m value of Al-7.7Zn-2.0Mg-1.9Cu-0.1Zr-0.1Sc alloy deformed 85% increased from 0.33 to 0.46 with increasing total elongation. This new TMT process was very simple and easy to make the sheets in the company.
자동차 차체재료용 Al-Mg-Si-Cr-Be-(Mn) 합금의 기계적 성질과 석출거동
우기도,황인오,나홍석,문호정 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.6
Al-Mg-Si base alloys have a good strength, formability, corrosion resistance and bake hardenability. But the bake hardenability of Al-Mg-Si-Cr-Be alloy is better than that of Al-Mg-Si alloy. Mn is added to improve the toughness in Al-Mg-Si alloys. But the precipitation behavior of Al-Mg-Si based alloys with large amount of Mn addition($gt;0.5 wt%) has not been reported yet. Therefore, the mechanical property and precipitation behavior of the Al-Mg-Si-Cr-Be alloy with 0.5-1.5%Mn was observed using the hardness and tensile tests, differential scanning calorimetry(DSC) and transmission electron microscope(TEM). The tensile strength of Al-Mg-Si-Cr-Be alloy increased with the increase of Mn content without decrease of elongation due to the increase of Mn dispersoid. Therefore, the combination of properties such as strength and ductility in the Al-Mg-Si-Cr-Be-Mn alloy was better than that in the Al-Mg-Si-Cr-Be alloy. The formation energy of β$quot; phase of Al-Mg-Si-Cr-Be alloy is decreased by the addition of Mn. But The precipitation of β' phase of Al-Mg-Si-Cr-Be alloy is little affected by the addition of Mn.
우기도,김동건,이현범,문민석,기웅,권의표,Woo, Kee-Do,Kim, Dong-Keon,Lee, Hyun-Bom,Moon, Min-Seok,Ki, Woong,Kwon, Eui-Pyo 한국재료학회 2008 한국재료학회지 Vol.18 No.6
Single-crystal $ZnIn_2S_4$ layers were grown on a thoroughly etched semi-insulating GaAs (100) substrate at $450^{\circ}C$ with a hot wall epitaxy (HWE) system by evaporating a $ZnIn_2S_4$ source at $610^{\circ}C$. The crystalline structures of the single-crystal thin films were investigated via the photoluminescence (PL) and Double-crystal X-ray rocking curve (DCRC). The temperature dependence of the energy band gap of the $ZnIn_2S_4$ obtained from the absorption spectra was well described by Varshni's relationship, $E_g(T)=2.9514\;eV-(7.24{\times}10^{-4}\;eV/K)T2/(T+489K)$. After the as-grown $ZnIn_2S_4$ single-crystal thin films was annealed in Zn-, S-, and In-atmospheres, the origin-of-point defects of the $ZnIn_2S_4$ single-crystal thin films were investigated via the photoluminescence (PL) at 10 K. The native defects of $V_{Zn}$, $V_S$, $Zn_{int}$, and $S_{int}$ obtained from the PL measurements were classified as donor or acceptor types. Additionally, it was concluded that a heat treatment in an S-atmosphere converted $ZnIn_2S_4$ single crystal thin films into optical p-type films. Moreover, it was confirmed that In in $ZnIn_2S_4$/GaAs did not form a native defects, as In in $ZnIn_2S_4$ single-crystal thin films existed in the form of stable bonds.
Al-Li-(Cu , Zr) 합금에서 시효에 따른 δ' 상의 형상 및 입자크기분포의 변화
우기도,조현기 ( K . D . Woo,H . K . Cho ) 한국열처리공학회 1994 熱處理工學會誌 Vol.7 No.2
The present work was aimed to examine the changes of the shape and particle size distribution(PSD) of δ` particles on ageing in Al-Li-(Cu, Zr) alloys which had low density, high specific strength and stiffness. Increasing ageing time and temperature resulted in particles whose aspect ratio tended toward 1. The aspect ratio of δ` particles was not dependent upon the ageing temperature and time in Al-Li-Cu alloy but was dependent upon them in Al-Li-Zr alloy. The PSD of δ` particles in Al-Li-Zr alloy skewed to the right hand compared with that in Al-Li-Cu alloy, because Al₃Zr phase in Al-Li-Zr alloy formed before ageing promoted the precipitation and growth of δ` phase. Therefore, the PSD of the δ` particles was found to be affected by the presence of Al₃Zr particles. The growth rate of δ` phase was not affected by the existence of the third transition phase T₁formed by the addition of Cu in Al-Li alloy but was affected by the existence of Al₃Zr formed by the addition of Zr in Al-Li alloy.
생체의학 임플란트재료로서 Ti-Nb계 합금의 조직과 기계적 성질에 미치는 HEMM의 영향
우기도,최갑송,이현범,김인용,Woo, Kee-Do,Choi, Gab-Song,Lee, Hyun-Bum,Kim, In-Yong,Zhang, Deliang 한국재료학회 2007 한국재료학회지 Vol.17 No.11
Al-42wt%Nb powder was prepared by high-energy mechanical milling(HEMM). The particle size, phase transformation and microstructure of the as-milled powder were investigated by particle size distribution (PSD) analyzer, scanning electron microscopy (SEM), X-ray diffractometery (XRD), transmission electron microscopy (TEM)and differential thermal analysis (DTA). The milled powders were heated to a sintering temperature at 1000C with under vaccum with vaccum tube furnace. Microstructural examination of sintered Ti-42wt%Nb alloy using 4h-milled powder showed Ti-rich phases (${\alpha}$-Ti) which are fine and homogeneously distributed in the matrix (Nb-rich phase: ${\beta}$-Ti). The sintered Ti-42wt%Nb alloy with milled powder showed higher hardness. The microstructure of the as quenched specimens fabricated by sintering using mixed and milled powder almost are same, but the hardness of as quenched specimen fabricated by using mixed powder increased due to solution hardening of Nb in Ti matrix. The aging effect of these specimens on microstructural change and hardening is not prominent.
스파크플라즈마 소결에 의한 Ti-Nb-Zr-Mo-CPP 생체복합재의 기계적 성질 및 생체적합성
우기도,김상미,김동건,김대영,강동수,Woo, Kee Do,Kim, Sang Mi,Kim, Dong Gun,Kim, Dae Young,Kang, Dong Soo 한국재료학회 2013 한국재료학회지 Vol.23 No.2
The Ti-6Al-4V extra low interstitial (ELI) alloy has been widely used as an orthopedic implant material because of its excellent mechanical properties and biocompatibility. However, it still has many problems, including a high elastic modulus and toxicity of the Al and V elements. Therefore, non-toxic biomaterials with a low elastic modulus need to be developed. A high energy mechanical milling (HEMM) process is introduced to improve the effect of sintering. Rapid sintering of spark plasma sintering (SPS) under pressure was used to make an ultra fine grain of Ti-25 wt.%Nb-7 wt.%Zr-10 wt.%Mo-(10 wt.%CPP) composites with bio-attractive elements for increasing strength. These composites were fabricated by SPS at $1000^{\circ}C$ at 60 MPa using HEMM powders. During the sintering process, $CaTiO_3$, TixOy, and CaO were formed because of the reaction between Ti and CPP. The effects of CPP content on the physical and mechanical properties of the sintered Ti-Nb-Zr-Mo-CPP composites were investigated. The biocompatibility and corrosion resistance of the Ti-Nb-Zr-Mo alloys were improved by the addition of CPP.
무가압 침투법에 의해 제조된 Al-5Mg-X(Si,Cu,Ti)SiCp 복합재료의 조직 및 마멸특성
우기도,김석원,안행근,정진호 한국주조공학회 2000 한국주조공학회지 Vol.20 No.4
Metal matrix composites(MMCs) reinforced with hard particles have many potential application in aerospace structures, auto parts, semiconductor package, heat resistant panels, wear resistant materials and so on. In this work, the effect of SiC partio sizes(50 and 100㎛) and additional elements such as Si, Cu and Ti on the microstructure and the wear property of Al-5Mg-X(Si, Cu, Ti)/SiC_p composites produced by pressureless infiltration method have been investigated using optical microscopy, scanning eletron microcopy(SEM) with EDS(energy dispersive spectrometry), hardness test, X-ray diffractometer(XRD) and wear test. In present study, the sound Al-5Mg-X(Si, Cu, Ti)/SiC_p(50 and 100㎛) composites were fabricated by pressureless infiltration method. The Al-5Mg-0.3Si-O.1Cu-O.1Ti/SiC_p composite with 50㎛ size of SiC particle has higher hardness and better wear property than any other composite with 100㎛ size of SiC particle produced by pressureless infiltration method. The hardness and wear property of Al-5Mg/SiC_p(50 and 100㎛) composites were enhanced by the addition of Si, Cu and Ti in Al-5%Mg matrix alloy.