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Al-Mg계 합금과 Al-Si계 합금의 다이캐스팅 응고과정의 차이
최세원,김영찬,조재익,강창석,홍성길,Choi, Se-Weon,Kim, Young-Chan,Cho, Jae-Ik,Kang, Chang-Seog,Hong, Sung-Kil 한국재료학회 2012 한국재료학회지 Vol.22 No.2
The effect of the alloy systems Al-Mg alloy and Al-Si alloy in this study on the characteristics of die-casting were investigated using solidification simulation software (MAGMAsoft). Generally, it is well known that the casting characteristics of Al-Mg based alloys, such as the fluidity, feedability and die soldering behaviors, are inferior to those of Al-Si based alloys. However, the simulation results of this study showed that the filling pattern behaviors of both the Al-Mg and Al-Si alloys were found to be very similar, whereas the Al-Mg alloy had higher residual stress and greater distortion as generated due to solidification with a larger amount of volumetric shrinkage compared to the Al-Si alloy. The Al-Mg alloy exhibited very high relative numbers of stress-concentrated regions, especially near the rib areas. Owing to the residual stress and distortion, defects were evident in the Al-Mg alloy in the areas predicted by the simulation. However, there were no visible defects observed in the Al-Si alloy. This suggests that an adequate die temperature and casting process optimization are necessary to control and minimize defects when die casting the Al-Mg alloy. A Tatur test was conducted to observe the shrinkage characteristics of the aluminum alloys. The result showed that hot tearing or hot cracking occurred during the solidification of the Al-Mg alloy due to the large amount of shrinkage.
Al-Si-Mg-Cu 합금의 자동차 엔진 사용 온도에서 열처리 조건에 따른 열확산도 변화
최세원,Choi, Se-Weon 한국재료학회 2021 한국재료학회지 Vol.31 No.11
The precipitation effect of Al-6%Si-0.4%Mg-0.9%Cu-(Ti) alloy (in wt.%) after various heat treatments was studied using a laser flash device (LFA) and differential scanning calorimetry (DSC). Solid solution treatment was performed at 535 ℃ for 6 h, followed by water cooling, and samples were artificially aged in air at 180 ℃ and 220 ℃ for 5 h. The titanium-free alloy Al-6%Si-0.4%Mg-0.9%Cu showed higher thermal diffusivity than did the Al-6%Si-0.4%Mg-0.9%Cu-0.2%Ti alloy over the entire temperature range. In the temperature ranges below 200 ℃ and above 300 ℃, the value of thermal diffusivity decreased with increasing temperature. As the sample temperature increased between 200 ℃ and 400 ℃, phase precipitation occurred. From the results of DSC analysis, the temperature dependence of the change in thermal diffusivity in the temperature range between 200 ℃ and 400 ℃ was strongly influenced by the precipitation of θ'-Al<sub>2</sub>Cu, β'-Mg<sub>2</sub>Si, and Si phases. The most important factor in the temperature dependence of thermal diffusivity was Si precipitation.
Si 나노 입자와 Er<sup>3+</sup>를 공첨가한 SiO<sub>2</sub>계 도파로의 제작과 평가
최세원,고영호,장세훈,오익현,강창석,Choi, Se-Weon,Ko, Young-Ho,Chang, Se-Hun,Oh, Ik-Hyun,Kang, Chang-Seog 한국재료학회 2007 한국재료학회지 Vol.17 No.4
[ $SiO_2$ ]thin films containing Si-nanocrystals and $Er^{3+}$ were fabricated by the RF-sputtering method. Intense emission of $Er^{3+}$ was observed at 1530 nm region after the annealing of the film at $1050^{circ}C$ for 5 min. Channel waveguides were fabricated using such films for the core. The films containing Si higher than 2.4 at% exhibited the change in stress from compression to tension after annealing, which induced the fatal loss-increase in waveguide. The optical gain might be attained by the Er-doped waveguide with Si lower than 2.4 at% by a visible-light-excitation.
시효 열처리 된 Al-Si-Mg-Cu-(Ti) 합금의 고온 열팽창 계수 변화
최세원,Choi, Se-Weon 한국열처리공학회 2021 熱處理工學會誌 Vol.34 No.5
The relationship between precipitation and coefficient of thermal expansion of Al-6%Si-0.4%Mg-0.9%Cu-(Ti) alloy (in wt.%) after various heat treatments were studied by the thermodynamic analyzer (TMA) and differential scanning calorimetry (DSC). Solution heat treatment of the alloy was carried out at 535℃ for 6 h followed by water quenching, and the samples were artificially aged in the air at 180℃ and 220℃ for 5 h. The coefficient of thermal expansion (CTE) curve showed some residual strain and decreased with increasing aging temperature. The CTE curves changed sharply in the temperature range of 200℃ to 400℃, and the corresponding peak shifted for the aged samples due to the change in the precipitation behavior of the secondary phase. These transformation peaks in the aged sample are related to the volume of the precipitation of the Si phase as determined by DSC analysis. The change in CTE is mainly caused by the precipitation of the Si phase in the Al-Si alloy, and the size of the change occurs simultaneously with the size of the precipitate.
열처리에 따른 제2상 석출이 Al-4.5%Cu 합금의 열 물성에 미치는 영향
최세원,Choi, Se-Weon 한국재료학회 2020 한국재료학회지 Vol.30 No.8
The relationship between the precipitation of secondary phase and the thermal properties of Al-4.5%Cu alloy (in wt.%) after various heat treatments has been studied. Solid solution treatment of alloy was performed at 808 K for 6 hours, followed by warm water quenching; then, the samples were aged in air at 473 K for different times. The thermal diffusivity of the Al-4.5%Cu alloy changed with the heat treatment conditions of the alloy at temperatures below 523 K. The as-quenched specimen had the lowest thermal diffusivity, and as the artificial aging time increased, the thermal diffusivity of the specimen increased in the temperature range between 298 and 523 K. For the specimen aged for five hours, the thermal conductivity was 12% higher than that of the as-quenched specimens at 298 K. It is confirmed that the thermal diffusivity and thermal conductivity of the Al-4.5%Cu alloy significantly depend on their thermal history at temperatures below 523 K. The precipitation and dissolution of the Al<sub>2</sub>Cu phase were confirmed via DSC for the alloys, and the formation of coefficient of thermal expansion peaks in TMA was caused by precipitation. The precipitation of supersaturated solid solution of Al-4.5%Cu alloys had an additional linear expansion of ≈ 0.05 % at 643 K during thermal expansion measurement.
알루미늄 주조용 SKD61 금형강의 표면처리 방법에 따른 특성 평가
최세원 ( Se-weon Choi ),김철우 ( Cheol-woo Kim ),김용호 ( Yong-ho Kim ),유효상 ( Hyo-sang Yoo ) 한국열처리공학회 2021 熱處理工學會誌 Vol.34 No.6
Arc ion plating (AIP), laser cladding, and nitriding are methods that can prevent mold damage or repair and create cracks and breakages on the die surface. The dissolution and soldering behavior of coated SKD61 by using arc ion plating, laser cladding, and nitriding was investigated. The structure of the coating was investigated as a function of deposition conditions by X-ray diffraction and the crystallographic orientation was determined using the texture factor. The TiAlN film deposited with AIP showed excellent corrosion resistance in the molten aluminum alloy at 680℃. In this paper, we have detailed the corrosion and mass loss phenomena associated with these steel-cast metal interactions. (Received Septemer 23, 2021; Revised Septemer 30, 2021; Accepted October 12, 2021)
방전플라즈마 소결법을 이용한 Fe-Cr계 금속 연결재의 특성 평가
장세훈,홍지민,최세원,김휘준,안중호,오익현,Chang, Se-Hun,Hong, Ji-Min,Choi, Se-Weon,Kim, Hwi-Jun,Ahn, Jung-Ho,Oh, Ik-Hyun 한국재료학회 2007 한국재료학회지 Vol.17 No.8
Fe based SOFC(Solid Oxide Fuel Cell) interconnector was fabricated by using the spark plasma sintering process and its microstructure and mechanical properties were investigated in this study. To fabricate the interconnector, the Fe-26Cr powder was mixed with the Ag (5, 10, 20wt.%) particles. In the Fe-26Cr-Ag sintered bodies, the Ag particles were almost dispersed at the grain boundary of the Fe-26Cr. The sintered bodies have the density of 87.2-97.5%, the density increases with increasing Ag content at sintering temperature of $850^{\circ}C$. Also, the compressive yield strength increases with increasing Ag content at the same sintering temperature.
스퍼터링 타겟재의 응용을 목적으로 하는 탄탈륨 소결체의 제작 및 평가
장세훈,최정철,최세원,오익현,Chang, Se-Hun,Choi, Jung-Chul,Choi, Se-Weon,Oh, Ik-Hyun 한국재료학회 2008 한국재료학회지 Vol.18 No.4
In this study, tantalum (Ta) compacts were fabricated in a spark plasma sintering (SPS) process and their microstructure and mechanical properties were investigated. Ta compacts with a density of 99% were successfully fabricated by controlling the sintering conditions of the current and the temperature. The density and hardness were increased as the sintering temperature increased. The $Ta_2C$ compound was observed at the surface of the compacts due to the contact between the Ta powder and graphite mold during the sintering process. The main fracture mode showed a mixed type with intergranular and transgranular modes having some roughness.
Al 합금과 STD61강의 소착에 미치는 첨가원소 Fe, Mn의 영향
김유미,홍성길,최세원,김영찬,강창석,Kim, Yu-Mi,Hong, Sung-Kil,Choi, Se-Weon,Kim, Young-Chan,Kang, Chang-Seog 한국재료학회 2012 한국재료학회지 Vol.22 No.4
Recently, various attempts to produce a heat sink made of Al 6xxx alloys have been carried out using die-casting. In order to apply die-casting, the Al alloys should be verified for die-soldering ability with die steel. It is generally well known that both Fe and Mn contents have effects on decreasing die soldering, especially with aluminum alloys containing substantial amounts of Si. However, die soldering has not been widely studied for the low Si aluminum (1.0~2.0wt%) alloys. Therefore, in this study, an investigation was performed to consider how the soldering phenomena were affected by Fe and Mn contents in low Si aluminum alloys. Each aluminum alloy was melted and held at $680^{\circ}C$. Then, STD61 substrate was dipped for 2 hr in the melt. The specimens, which were air cooled, were observed using a scanning electron microscope and were line analyzed by an electron probe micro analyzer. The SEM results of the dipping soldering test showed an Al-Fe inter-metallic layer in the microstructure. With increasing Fe content up to 0.35%, the Al-Fe inter-metallic layer became thicker. In Al-1.0%Si alloy, the additional content of Mn also increased the thickness of the inter-metallic layer compared to that in the alloy without Mn. In addition, EPMA analysis showed that Al-Fe inter-metallic compounds such as $Al_2Fe$, $Al_3Fe$, and $Al_5Fe_2$ formed in the die soldering layers.
방전플라즈마 소결공법에 의해 제작된 SOFC용 Ni-YSZ Anode의 특성평가
장세훈,최정철,최세원,김호성,오익현,Chang, Se-Hun,Choi, Jung-Chul,Choi, Se-Weon,Kim, Ho-Sung,Oh, Ik-Hyun 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.5
SOFC (Solid Oxide Fuel Cell) Ni-YSZ anode was fabricated by the spark plasma sintering (SPS) process and its microstructure and electrical properties were investigated in this study. The spark plasma sintering process was carried out at $800{\sim}1000^{\circ}C$ for holding time of 5 min under 40 MPa. To fabricate Ni-YSZ anode, the SPS processed specimens were reduced at $800^{\circ}C$ under $H_2$ atmosphere. The reduced specimens showed relative density of $48.4{\sim}64.8%$ according to sintering temperature. And also, the electrical conductivity of reduced specimens after sintering at 900 and $1000^{\circ}C$ showed $480{\sim}600$ (S/cm) values at the measuring range of $600{\sim}900^{\circ}C$.