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대한금속재료학회> 대한금속재료학회지> CaO-CaF2-SiO2 슬래그의 탈린능에 미치는 BaO 및 알카리계 금속 산화물의 첨가 효과

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CaO-CaF2-SiO2 슬래그의 탈린능에 미치는 BaO 및 알카리계 금속 산화물의 첨가 효과

Pyrometallurgy : Effect of BaO and Alkali metal oxides Additions in CaO - CaF2 - SiO2 Slags on Dephosphorization Capability

손상한(Sang Han Son) , 김의준(Eui Jun Kim) , 박종진(Jong Jin Pak)
  • : 대한금속재료학회
  • : 대한금속재료학회지 39권5호
  • : 연속간행물
  • : 2001년 05월
  • : 595-601(7pages)
대한금속재료학회지

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The effect of oxide additives, such as BaO, Li₂O, K₂O and Na₂O in CaO-CaF₂-SiO₂ slags on the equilibrium phosphorus distribution ratios, L_p between molten slags and Fe-C_(sat·)-P melts were studied at 1300℃. The effect of BaO addition on the increase in the L_p is more significant when it is added to the lower basicity slag. The small addition of Li₂O K₂O and Na₂O in CaO-CaF₂-SiO₂ slags significantly increases the L_p. The stability of Li₂O in slag is much higher than K₂O and Na₂O during the dephosphorization reaction. The correlation between the phosphate capacities of slags containing alkali metal oxides does not show the linear relationship with their optical basicities. The alkali metal oxides decrease the activity coefficient of phosphate ions in slag drastically, and thereby increase the dephosphorization capability of CaO based slags.

UCI(KEPA)

I410-ECN-0102-2009-580-005877911

간행물정보

  • : 공학분야  > 금속공학
  • : KCI등재
  • : SCOPUS
  • : 월간
  • : 1738-8228
  • : 2288-8241
  • : 학술지
  • : 연속간행물
  • : 1963-2022
  • : 7052


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60권9호(2022년 09월) 수록논문
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1Advances in Atomic Force Microscopy for the Electromechanical Characterization of Piezoelectric and Ferroelectric Nanomaterials

저자 : Kwanlae Kim

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 60권 9호 발행 연도 : 2022 페이지 : pp. 629-643 (15 pages)

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Given the social demand for self-powering wearable electronics, it is necessary to develop composite materials that exhibit both good flexibility and excellent piezoelectric performances. Intensive research on synthesis methods and devising characterization techniques for piezoelectric nanomaterials in various forms has been conducted. In particular, characterization techniques for piezoelectric nanomaterials require different approaches from those for conventional bulk materials. Atomic force microscopy (AFM)-based characterization techniques work based on the local physical interactions between the AFM tip and sample surfaces, making them an irreplaceable tool for studying the electromechanical properties of piezoelectric nanomaterials. Piezoresponse force microscopy (PFM), conductive AFM (C-AFM), and lateral force microscopy (LFM) are three representative AFM-based techniques used to characterize the piezoelectric and ferroelectric properties of nanomaterials. Coupled with the appearance of diverse novel nanomaterials such nanowires, free-standing nanorods, and electrospun nanofibers, AFM-based characterization techniques are becoming freer from artifacts and the need for quantitative measurements. PFM was initially developed to image the microstructures of piezoelectric materials, and well-calibrated techniques designed to realize quantitative measurements have been applied to nanomaterials. In contrast, C-AFM and LFM were initially used to measure the conductivity of diverse materials and the nanotribology of material surfaces. Over the last decade, they have proved their versatility and can now be used to evaluate the direct piezoelectric effect and the mechanical properties of piezoelectric nanomaterials. In these cases, systematic understanding with regard to the measurement principles is required for accurate measurements and analyses. In the present review article, we discuss earlier work in which AFM-based electromechanical characterization techniques were applied to nanomaterials to evaluate piezoelectric and ferroelectric properties. Also discussed is the importance of gaining a comprehensive understanding of the resulting signals.
(Received 17 May, 2022; Accepted 7 June, 2022)

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2열가소성 성형을 이용한 비정질 합금의 홀로그램 임프린팅 공정 최적화

저자 : 류욱하 ( Wook Ha Ryu ) , 류채우 ( Chae Woo Ryu ) , 김경준 ( Kyung Jun Kim ) , 곽민경 ( Min Kyung Kwak ) , 박은수 ( Eun Soo Park )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 60권 9호 발행 연도 : 2022 페이지 : pp. 644-653 (10 pages)

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The thermoplastic forming (TPF) process of metallic glass (MG) is a unique and powerful method that cannot be performed using conventional crystalline alloys. Because the mechanical and thermal properties of MGs are more favorable with smaller sample sizes, TPF is particularly useful for microscale and nanoscale part molding and micro-patterning. One of the promising commercial MG applications that can take full advantage of these characteristics is hologram patterning. Holograms can be used to identify unique brands, using characteristics with patterns that are difficult to replicate. Their excellent aesthetic qualities can also greatly contribute to increased product value. In this study, we developed and performed a TPF process for actual holographic imprinting with Mg-based MGs, and further investigated the TPF processing window, covering a wide range of temperature and process time conditions through thermal analysis, with ultra-fast heating rates ranging from 100 to 25000 K/s using Flash-DSC. The results of this study serve as a practical guide for identifying the full range of TPF processing windows including conventional and ultrafast heating conditions for micro-scale and nanoscale molding of various MGs. Moreover, a methodology is proposed to identify the general TPF processing window (η<108 Pa·s) and the ideal TPF processing window (η<104 Pa·s) by estimating the viscosity (η) of the supercooled liquid. Accordingly, this study is expected to be utilized to optimize the TPF process of MGs and promote the commercialization of related industries.
(Received 17 June, 2022; Accepted 27 June, 2022)

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3Enhancing mechanical properties of Mg-Gd-Y-Zn alloys via microalloying with Ce and La

저자 : Zhaobin Zhang , Jonghyun Kim , Hongxin Liao , Ki Buem Kim , Taekjib Choi , Taekyung Lee , Fusheng Pan

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 60권 9호 발행 연도 : 2022 페이지 : pp. 654-667 (14 pages)

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This study investigated the microstructure and mechanical properties of Mg-1Gd-1Y-1Zn (at.%) alloys containing designed amounts of Ce or La. The Mg5(Gd,Zn) phase formed in the as-cast Mg-Gd-Y-Zn-Ce/La alloys and disappeared after a homogenization treatment at 500℃ for 24 h. The addition of Ce and La resulted in the formation of Ce(Mg,Zn)12 and La(Mg,Zn)12 phases, respectively. Except for that, the Ce or La addition had no significant effect on the morphology, volume fraction, and type of the long-period stacking ordered (LPSO) phases in the Mg-Gd-Y-Zn alloy. The grain size decreased with increasing microalloying content because the heavy Ce and La atoms impeded atomic migration across the boundaries. The solute drag effect led to the formation of the rare earth texture in the extruded Mg-Gd-Y-Zn-Ce/La alloys, whose extent decreased with increasing microalloying content. The mechanical strength was improved by the addition of Ce or La at the sacrifice of ductility. In particular, La exhibited a stronger reinforcement ability than Ce when it was added to the Mg-Gd-Y-Zn alloys. Among the investigated chemical compositions, the Mg-1Gd-1Y-1Zn-0.3La alloy exhibited the highest strength because it had the finest grains, the highest volume fraction of the second phase, and the weakest texture intensity. Furthermore, the alloys showed an unusual yield asymmetry due to the difference in the deformation mode of the LPSO phase.
(Received 12 April, 2022; Accepted 20 June, 2022)

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4Effects of Electron Irradiation on the Properties of ZnO/Au/ZnO Films Deposited on Poly-Imide Substrates

저자 : Jin-kyu Jang , Yun-je Park , Yeon-hak Lee , Jae-wook Choi , Hyun-jin Kim , Sung-bo Heo , Young-min Kong , Daeil Kim

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 60권 9호 발행 연도 : 2022 페이지 : pp. 668-672 (5 pages)

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Transparent and conductive ZnO 50 nm/Au 8 nm/ZnO 50 nm tri-layer films were deposited on polyimide films by radio frequency (RF) and direct current (DC) magnetron sputtering at room temperature, and then the effect of electron irradiation on the crystallization, electrical resistivity and optical properties of the films was considered with X-ray diffraction, UV-visible spectrometer, Atomic force microscope and Hall measurement system. All the films were deposited at a fixed sputtering power, Ar gas flow rate, and distance between target and substrate, while the post-deposition electron irradiation energy was varied from 300 to 900 eV. The electron irradiated films exhibited a flatter surface than the as deposited films that were not electron irradiated, and the XRD patterns also revealed that the electron irradiated films had larger grain sizes than that of as deposited films. The films electron irradiated at 900 eV also showed a higher visible transmittance of 79.8% and a lower sheet resistance of 56.0 Ω/□. Post-deposition films electron irradiated at 900 eV showed a higher figure of merit of 1.86×10-3 Ω-1 than that of the as deposited film of 1.29×10-3 Ω-1. The optical band gap was also enhanced by electron irradiation. The films electron irradiated at 900 eV showed a higher optical band gap of 4.07 eV.
(Received 15 April, 2022; Accepted 17 June, 2022)

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5극저온 연료탱크용 고망간강과 스테인리스강 316L 이종금속 용접부의 가스텅스텐아크 용접재료별 기계적 성질 및 미세조직

저자 : 조철호 ( Chulho Cho ) , 남성길 ( Seongkil Nam ) , 유성훈 ( Sunghoon Yu ) , 최명환 ( Myeonghwan Choi ) , 강남현 ( Namhyun Kang )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 60권 9호 발행 연도 : 2022 페이지 : pp. 673-684 (12 pages)

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The gas tungsten arc (GTA) weldability of high-Mn (HMn) steel and austenitic stainless steel (STS) 316L using dissimilar metal welds (DMWs) was investigated, to fabricate a fuel tank for an LNG-fueled ship. Three types of welding fillers, HMn steel, STS 309LMo and Inconel 625, were applied to the DMWs. The weldability of the DMWs was examined by investigating mechanical properties at 25 and -196℃, followed by microstructural evolution and weld deformation. The GTA welding process was performed with a heat input range of 0.72-1.89 kJ/mm. All of the fillers employed in the study produced reasonable mechanical properties and low levels of precipitation, such as M7C3 and Fe3C. However, the DN specimen using the Inconel 625 filler exhibited reduced ductility in the bending test. This was attributed to Nb-carbide precipitations at dendrite boundaries at the root weld. The DM specimen using HMn filler experienced severe thermal deformation because it had a relatively higher coefficient of thermal expansion than the other fillers during heating by arc and solidification. Therefore, STS 309LMo and HMn wires were determined to be the appropriate fillers for the DMW of HMn steel and STS 316L for cryogenic applications, and the HMn wire requires attention to weld deformation.
(Received 18 April, 2022; Accepted 21 June, 2022)

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6Effects of Fillers on the Hydration Behaviors of Tricalcium Silicate Scaffolds Fabricated by Fused Deposition Modeling

저자 : Yeongjin Koo , Yoonjoo Lee , Myung-hyun Lee , Seog Young Yoon

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 60권 9호 발행 연도 : 2022 페이지 : pp. 685-693 (9 pages)

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With the development of additive manufacturing technology, many types of materials are being utilized, and methods of printing the materials and characteristics of their hydration properties are being studied in the fields of construction and biotechnology. Tricalcium silicate (C3S), which is used as a cement material or biomaterial, is a representative hydraulic material. In previous research, scaffolds were printed via fused deposition modeling and the deformation properties during the hydration process of the printed scaffold were investigated. C3S, like ceramic materials, requires post-processing such as curing after printing, and volumetric deformation occurs during this process. Deformation information is very important to ensure the numerical value of the final product, as well as to suppress the possibility of deformation. In this study, silica, hydroxyapatite (HA), and alumina were mixed with three types of fillers to print a C3S support, which was then cured through a two-step process. In this process, HA and silica, which have good hydrophilicity, exhibited high strength due to the suppression of scaffold deformation. It was confirmed that the smaller the particle size, the more effective it was in obtaining a stable hydrated print.
(Received 10 May, 2022; Accepted 7 July, 2022)

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7단일벽 탄소나노튜브와 다중벽 탄소나노튜브 사용에 따른 고분자 복합체의 기계적, 전기적 물성

저자 : 강병호 ( Byung-ho Kang ) , 허오녕 ( Oh-nyoung Hur ) , 홍순국 ( Soon-kook Hong ) , 박성훈 ( Sung-hoon Park )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 60권 9호 발행 연도 : 2022 페이지 : pp. 694-700 (7 pages)

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To manufacture composites with required properties, it is extremely important to select an appropriate filler. Carbon-based nano materials such as carbon black, graphene and carbon nanotube (CNT) have been extensively investigated as reinforcing and conducting fillers. Because of their high aspect ratio coupled with superior physical properties, 1-dimensional CNTs are ideal as filler materials to impart electrical conductivity to insulating polymers, while enhancing mechanical strength. In this study, we investigated the piezo-resistive and mechanical properties of composites consisting of two types of CNT classified as multi-walled CNT (MWNT) or single-walled CNT (SWNT) depending on the number of walls. Since MWNT and SWNT have different physical properties such as specific surface area and aspect ratio, this can affect the composite's performance. To more effectively evaluate the effect of MWNTs and SWNTs in composites, we used thermoplastic polyurethane (TPU) as a matrix, which is an insulating stretchable elastomer. Morphological and mechanical/electrical characterizations were conducted to determine differences in the MWNT and SWNT composites. In addition, we conducted dynamic strain sensing tests on each type of CNT composites to compare the sensitivity as a strain sensor. Differences in piezo-resistive behaviors were attributed to the loss of electrical contact points during stretching. These results can serve as a useful design guideline for the wider use of CNT composites.
(Received 13 April, 2022; Accepted 21 June, 2022)

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8DIC를 활용한 선압축과 후열처리 공정을 거친 AZ31 마그네슘 압연재의 인장 변형 거동 분석

저자 : 이교명 ( Gyo Myeong Lee ) , 김정은 ( Jung Eun Kim ) , 박성혁 ( Sung Hyuk Park )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 60권 9호 발행 연도 : 2022 페이지 : pp. 701-712 (12 pages)

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This study investigates the effects of precompression and subsequent annealing on the tensile deformation behavior of a rolled AZ31 Mg alloy at room temperature using digital image correlation (DIC). When the as-rolled sample (AR sample) is subjected to precompresssion along the rolling direction (RD) and transverse direction (TD), the sample's texture changes from the typical normal direction (ND)-oriented basal texture to the RD- and TD-oriented basal textures, respectively, because of the lattice reorientation by {10-12} twinning. During tension along the RD, the AR sample and the sample precompressed along the TD and subsequently annealed at 250 ℃ (TDCA sample) accomodate the tensile strain via dislocation slip, resulting in high yield strengths and slip-dominant strain-hardening behaviors. In contrast, the sample precompressed along the RD and subsequently annealed at 250 ℃ (RDCA sample) exhibits a low yield strength and twinningdominant strain-hardening behavior, owing to the vigorous activation of {10-12} twinning during tension. DIC results reveal that in the AR sample, noticeable strain localization occurs at an early stage of tensile deformation due to the difficulty of accommodating strain along the thickness direction. In the RDCA sample, strain distribution is relatively homogeneous via {10-12} twinning, but the rapid strain hardening caused by abundant {10-12} twins causes premature crack initiation. Because the basal planes of most grains of the TDCA sample are aligned parallel to the thickness direction, the thickness strain is effectively accommodated via prismatic slip, resulting in the highest tensile elongation among the three samples.
(Received 23 May, 2022; Accepted 6 July, 2022)

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9기계학습 모델 복잡도에 따른 템퍼드 마르텐사이트 경도 예측 정확도 비교 연구

저자 : 전준협 ( Junhyub Jeon ) , 김동응 ( Dongeung Kim ) , 홍준호 ( Jun-ho Hong ) , 김휘준 ( Hwi-jun Kim ) , 이석재 ( Seok-jae Lee )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 60권 9호 발행 연도 : 2022 페이지 : pp. 713-721 (9 pages)

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We investigated various numerical methods including a physical-based empirical equation, linear regression, shallow neural network, and deep learning approaches, to compare their accuracy for predicting the hardness of tempered martensite in low alloy steels. The physical-based empirical equation, which had been previously proposed with experimental data, was labelled and used in the present study. While it had a smaller number of coefficients, the prediction accuracy of the physical-based empirical equation was almost similar to that of the regression model based on the response surface method. The prediction accuracy of the machine learning models clearly improved as the number of layers increased and became more complicated in structure before the model began to overfit. The key point we found was that a single layered neural network model with optimized hyperparameters resulted in similar or better hardness prediction performance compared to deep learning models with a more complex architecture. We also analyzed 18 research papers from the literature which used neural network models to predict the hardness of steels. Only two recent papers adopted a convolutional neural network, as a kind of deep learning model, in a new attempt to predict hardness. The other 16 papers from 1998 to 2021 commonly chose shallow neural network models because a more complicated model is less effective than a simple model for regression problems with well-labeled experimental data in materials science and engineering.
(Received 3 June, 2022; Accepted 8 July, 2022)

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1초음파법에 의한 중탄소강에서의 시멘타이트 구상화율 평가

저자 : 김준수(J . S . Kim) , 변재원(Jai Won Byeon) , 권소인(S . I . Kwun) , 박은수(U . S . Park)

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 39권 5호 발행 연도 : 2001 페이지 : pp. 493-502 (10 pages)

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An attempt was made to evaluate the change of microstructures and mechanical properties with increasing spheroidizing time in a cold heading steel, containing proeutectoid ferrite and pearlite, by the ultrasonic attenuation and velocity measurements. Ultrasonic velocity was not sensitive to the microstructural changes, resulting from spheroidization heat treatment to produce various mean aspect ratio, mean equivalent size and number of cementite particles per unit area and ferrite grain size. Ultrasonic attenuation was initially decreased and then increased with increasing spheroidizing time. A good correlation between ultrasonic attenuation coefficient and mechanical properties such as hardness and tensile strength was found.

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2Nb 이 첨가된 A286 초내열합금의 고온저주파 피로에서 피로균열의 천이에 영향을 미치는 인자에 관한 연구

저자 : 노병섭(Byung Sup Rho) , 남수우(Soo Woo Nam)

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 39권 5호 발행 연도 : 2001 페이지 : pp. 503-510 (8 pages)

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Continuous low cycle fatigue tests have been conducted on Nb-A286 Fe-base superalloy in an air atmosphere at the temperature range of 25 to 650℃ to investigate the transition of fatigue cracking with test temperature and applied strain range. The intergranular fatigue cracking at high temperatures was due to the precipitation of the η phase at the grain boundary assisted by the applied stress during low cycle fatigue. It is investigated whether the precipitate at the grain boundary provides the site for the grain boundary cavitation, which induces the intergranular cracking in low cycle fatigue. The fatigue cracking mode changes from the transgranular mode to the predominantly intergranular mode with the applied strain range. The change of the fatigue cracking with strain range is induced by the combination of mutually competing factors involving the grain boundary precipitate, the density of the slip band, and the concentration of stress at points where the slip bands impinge upon the grain boundaries.

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3무가압침투법으로 제조된 SiC 입자 강화 A1 합금 기지 복합재료의 고온 크립 거동에 기지 합금 조성이 미치는 영향

저자 : 송명훈(Myong Hun Song) , 권훈(Hoon Kwon) , 김용석(Yong Suk Kim)

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 39권 5호 발행 연도 : 2001 페이지 : pp. 511-520 (10 pages)

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High temperature creep behaviour of 20 vol.% SiC particle reinforced 5052 Al, 6061 Al and 7075 Al alloy matrix composites was studied at temperatures of 633, 663, and 693K under the applied stress range of 25∼100 ㎫. The composites were manufactured by the pressureless infiltration technique. The composites showed high apparent stress exponent and activation energy. The 7075 Al matrix composite showed the highest creep strength at 633K, while at 693K the 5052 Al matrix composite had the highest creep resistance. The creep strength of the 7075 Al matrix composite decreased rapidly with increase of the temperature. True stress exponent of the composites was measured as 5 and major creep mechanism of the composites was found to be lattice self-diffusion of the matrix alloy. Different temperature-dependence of the composites` creep strength and the threshold stress (including its origin) were attributed to different amount of precipitates and aluminum nitrides in the matrix alloys.

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4Zr 첨가가 Cu - 6Ni - 2Mn - 2Sn - 2Al 합금의 인장 및 부식 특성에 미치는 영향

저자 : 서영익(Y . I . Seo) , 김상식(S . S . Kim) , 김기원(K . W . Kim) , 한승전(S . Z . Han) , 김창주(C . J . Kim)

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 39권 5호 발행 연도 : 2001 페이지 : pp. 521-527 (7 pages)

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In the present study, tensile and corrosion properties of Cu-6Ni-2Mn-2Sn-2Al alloy, with and without Zr addition, were examined. Even though the addition of Zr refined the grain structure of Cu-6Ni-2Mn-2Sn-2Al alloy, the improvement in tensile property was not significant. The addition of Zr, however, greatly improved the corrosion resistance of the alloy in NaCl aqueous solution. The potentiodynamic study clearly demonstrated that the Zr addition substantially reduced the current density of Cu-6Ni-2Mn-2Sn-2Al alloy in 3.5% NaCl solution. The enhanced corrosion resistance with Zr appeared to be due to the reduced Sn segregation during solidification. The stress corrosion cracking study reflected the result of potentiodynamic study in the present study. The Zr-added specimen showed no reduction in tensile ductility after exposure to 3.5% NaCl aqueous solution for 20 days with an applied stress of 80% yield strength, while the tensile elongation of non-Zr added specimen was reduced approximately 10% after the exposure. The reduced Sn segregation during solidification in believed to be the main reason for the improved corrosion property of Zr-containing Cu-6Ni-2Mn-2Sn-2Al alloys.

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5고에너지 전자빔투사방법에 의한 Tic / SUS304 표면복합재료의 제조와 미세조직분석

저자 : 이종민(Jong Min Lee) , 어광준(Kwang Jun Euh) , 오준철(Jun Cheol Oh) , 이성학(Sung Hak Lee)

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 39권 5호 발행 연도 : 2001 페이지 : pp. 528-534 (7 pages)

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The present study is concerned with fabrication and microstructural analysis of TiC/SUS304 surface composites using irradiation of accelerated high-energy electron beam. Three kinds of powder/flux mixtures, i.e., TiC, (Ti+C), and (Ti+SiC) powders with 40 wt.% of CaF₂ flux, were placed on an SUS304 stainless steel substrate, which was then irradiated with electron beam. TiC agglomerates and pores were found in the surface composite layer fabricated by irradiation of TiC powders because of insufficient melting of TiC powders. In the composite layer fabricated by irradiation of Ti and C powders having lower melting points than TiC powders, a number of primary TiC carbides were precipitated without forming TiC agglomerates or pores. This indicated the more effective TiC precipitation obtained from the melting of Ti and C powders, instead of TiC powders. The hardness and wear resistance of the surface composite layer were directly influenced by hard primary TiC carbides, and thus were two to three times greater than those of the stainless steel substrate.

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6고에너지 전자빔 투사방법으로 제조된 Ti-6Al-4V 표면합금화 재료의 미세조직과 마모특성

저자 : 오준철(Jun Cheol Oh) , 이성학(Sung Hak Lee)

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 39권 5호 발행 연도 : 2001 페이지 : pp. 535-545 (11 pages)

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The present study is concerned with the microstructural analysis and the evaluation of hardness and wear properties of Ti-6Al-4V surface-alloyed materials fabricated by high-energy electron beam. The mixtures of TiC, TiN, or TiC+TiN powders and CaF₂ flux were deposited on a Ti-6Al-4V substrate, and then electron beam was irradiated on these mixtures using an electron beam accelerator. In the specimens processed with a flux mixing ratio of 50 wt.%, the surface-alloyed layers of 1 ㎜ in thickness were homogeneously formed without defects, and contained a large amount (over 30 vol.%) of precipitates such as TiC, TiN, (Ti_xAl(1-x).)N, and TiC_xN(1-x) in the martensitic or N-rich acicular α-Ti matrix. This microstructural modification including the formation of hard precipitates and hardened matrices in the surface-alloyed layers improved hardness and wear resistance. Particularly in the TiN/Ti surface-alloyed material, the wear resistance was greatly enhanced by ten times higher than that of the Ti alloy substrate. These findings suggested that the surface-alloying using high-energy electron beam irradiation was economical and useful for the development of titanium-base surface-alloyed materials with improved hardness and wear properties.

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7반복겹침 접합압연으로 제조된 A1100 알루미늄합금 판재의 기계적 특성

저자 : 김향욱(Hyoung Wook Kim) , 진선화(Sun Hwa Jin) , 강석봉(Suk Bong Kang)

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 39권 5호 발행 연도 : 2001 페이지 : pp. 546-552 (7 pages)

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In this study, the microstructure and mechanical properties of A1100 aluminum alloy sheets manufactured by the Accumulative Roll Bonding(ARB) process were investigated. Hot rolled A1100 sheets were highly strained up to a true strain of 6.32 at room temperature by the ARB process. These sheets were recrystallized at the temperature range of 150℃ to 400℃ for 1hr. The ARB process was repeated up to 6 cycles and well bonded sheets were obtained successfully. The hardness and tensile strength of 6th ARBed specimen(true strain : 6.32) are three times higher than those of a hot rolled sheet. After recrystallization treatment at 200℃, the specimen has ultra-fine grain structures with grain size of less than 1 ㎛. In case of annealing at 300℃ for 1hr., the microstructures of the specimens consist of fully recrystallized grain structure with the grain size less than 7 ㎛.

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8온간 ECAP 법에 의해 제조된 5083 Al 합금의 미세조직과 기계적 특성

저자 : 강효경(Hyo Gyoung Kang) , L . Bachelard , 김향욱(Hyoung Wook Kim) , 강석봉(Suk Bong Kang)

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 39권 5호 발행 연도 : 2001 페이지 : pp. 553-559 (7 pages)

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The microstructure and mechanical properties have been investigated on a commercial 5083 aluminum alloy processed by the equal-channel angular pressing (ECAP) at 473K. The microstructure of a single pass sample consisted of elongated subgrains. Increasing the number of pass led to very fine equilibrium grains having high angle grain boundaries. The 0.2% yield stress and hardness after a single pass increased greatly, and then kept constant with additional straining. On the other hand, the elongation to failure of a single pass sample decreased a little to compare with sample before ECAP, but there was no further reduction with additional straining. Recrystallization partially occurred in ECAPed 5083 aluminum alloy when annealed at 523K for 1 hr, and completely finished when annealed only at 573K for 1 hr. With increasing the number of pass, the onset temperature of recrystallization decreased and the rate of softening increased.

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9Zn-Co 합금도금의 부식거동에 대한 코발트의 효과

저자 : 여준현(Jun Hyun Yeo) , 김정구(Jung Gu Kim) , 이재융(Jae Ryung Lee)

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 39권 5호 발행 연도 : 2001 페이지 : pp. 560-565 (6 pages)

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Recently Zn-Co alloy coating has been studied because minute additions of cobalt to zinc decrease its rate of corrosion. The corrosion behavior of electrodeposited Zn-Co alloy coatings with various contents of Co was compared with pure Zn coating using electrochemical test and electrochemical impedance spectroscopy (EIS) measurement in 3.5 wt% NaCl solution and surface analysis. In immersion test, the corrosion potential of all Zn-Co coatings was higher than that of pure Zn coating. Corrosion current density for the 0.9 wt%Co and 5.0 wt%Co was lower than that for pure Zn coating. Dezincification which occurred in the corrosion process made a Co-rich barrier in the coating layer and only 0.9 wt%Co and 5.0 wt%Co had an effective Co-rich barrier. The 58.0 wt%Co exhibited the highest current density owing to the localized corrosion at large cracks. The 0.9 wt%Co and 5.0 wt%Co, with a more active corrosion potential, were galvanically corroded at cracks in the coating to protect the exposed substrate cathodically. Whereas on the 58.0 wt%Co, anodic dissolution and galvanic corrosion of the substrate were concentrated at coating defects by a large cathode(58.0 wt%Co coating) and anode(substrate) surface area ratio. EIS and EPMA results confirmed that cobalt enrichment, together with the zinc corrosion products, acts as a barrier layer reducing the total corrosion rate.

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10인듐과 주석막의 중간층이 ITO/Si 접촉 저항에 미치는 영향

저자 : 유호진(Ho Jin Ryu) , 강진모(Jin Mo Kang) , 한영건(Young Gun Han) , 김동환(Dong Hwan Kim) , 박정호(Jung Ho Pak) , 박원규(Won Kyu Park) , 양명수(Myoung Su Yang)

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 39권 5호 발행 연도 : 2001 페이지 : pp. 566-570 (5 pages)

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Indium and tin layers were used as the diffusion barriers between the indium-tin oxide (ITO) and poly-Si in order to reduce the contact resistance. ITO/Si contacts should be adopted in thin-film transistor liquid crystal display (TFT LCD) for simplifying the fabrication process. For 5 ㎚ thick In and Sn layers, 10-minute annealing at 250℃ was performed to minimize the loss in the optical transmittance. With In and Sn layers, contact resistance values of 5×10^(-3) ∼ 4×10^(-3)Ω㎠ were obtained. These values were higher than those measured from the conventional ITO/Mo/Al/Si contacts (5×10^(-5) Ω㎠∼4 ×10^(-4)Ω㎠) but. lower than those obtained from ITO/Si contacts (about 1×10^(-1)Ω㎠) Sn was found to be stable after the annealing but In lost its function as a diffusion barrier by diffusion into Si.

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