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대한금속재료학회지 update

Korean journal of metals and materials

  • : 대한금속재료학회
  • : 공학분야  >  금속공학
  • : KCI등재
  • : SCI,SCOPUS
  • : 연속간행물
  • : 월간
  • : 1738-8228
  • : 2288-8241
  • : 금속재료학회지(~1999) → 대한금속재료학회지(2000~)

수록정보
59권1호(2021) |수록논문 수 : 9
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59권10호(2021년 10월) 수록논문
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KCI등재 SCI SCOPUS

1저온 템퍼링을 이용한 1.2 GPa급 페라이트계 경량철강 개발

저자 : 배효주 ( Hyo Ju Bae ) , 고광규 ( Kwang Kyu Ko ) , 박형석 ( Hyoung Seok Park ) , 정재석 ( Jae Seok Jeong ) , 김정기 ( Jung Gi Kim ) , 성효경 ( Hyokyung Sung ) , 설재복 ( Jae Bok Seol )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 10호 발행 연도 : 2021 페이지 : pp. 683-691 (9 pages)

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Previously reported low-Mn ferritic-based lightweight steels are potential candidates for industrial applications, however, they typically exhibit lower strength, with < 1 GPa and lower strength-ductility balance, than medium- and high-Mn austenitic lightweight steels. Herein, we introduce a low-temperature tempering-induced partitioning (LTP) treatment that avoids the strength-ductility dilemma of low-Mn ferritic-based steels. When the LTP process was performed at 330 ℃ for 665 s, the strength of typical ferritic base Fe-2.8Mn5.7Al0.3C (wt%) steel with heterogeneously sized metastable austenite grains embedded in a ferrite matrix, exceeded 1.1 GPa. Notably, the increased strength-ductility balance of the LTP-processed ferritic steel was comparable to that of the high-Mn based austenitic lightweight steel series. Using microscale to nearatomic scale characterization we found that the simultaneous improvement in strength and total elongation could be attributed to size-dependent dislocation movement, and controlled deformation-induced martensitic transformation.
(Received May 14 2021; Accepted July 5, 2021)

KCI등재 SCI SCOPUS

2나노구조의 ZrB2-Al2O3 복합재료 합성과 소결

저자 : 손인진 ( In-jin Shon )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 10호 발행 연도 : 2021 페이지 : pp. 692-697 (6 pages)

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ZrB2 is considered a candidate material for ultra-high temperature ceramics because of its high thermal conductivity, high melting point, and low coefficient of thermal expansion. Despite these attractive properties, ZrB2 applications are limited by its low fracture toughness below the brittle-ductile transition temperature. To improve its ductile properties, the approach universally utilized has been to add a second material to form composites, and to fabricate nanostructured materials. In this study a dense nanostructured ZrB2-Al2O3 composite was rapidly sintered using the pulsed current activated heating (PCAH) method within 3 min in one step, from mechanically synthesized powders of ZrB2 and Al2O3. Consolidation was accomplished using an effective combination of current and mechanical pressure. A highly dense ZrB2- Al2O3 composite with a relative density of up to 97.4% was fabricated using the simultaneous application of 70 MPa pressure and a pulsed current. The fracture toughness and hardness of the ZrB2-Al2O3 composite were 3.9 MPa.m1/2 and 1917 kg/㎟, respectively. The fracture toughness of the composite was higher than that of monolithic ZrB2.
(Received May 7 2021; Accepted July 20, 2021)

KCI등재 SCI SCOPUS

3ERNiFeCr-2 용가재 적용에 따른 CM247LC 초내열합금 용접부 응고균열 민감도 변화 거동

저자 : 김경민 ( Kyeong-min Kim ) , 정혜은 ( Hye-eun Jeong ) , 정예선 ( Ye-seon Jeong ) , 이의종 ( Uijong Lee ) , 이형수 ( Hyungsoo Lee ) , 서성문 ( Seong-moon Seo ) , 천은준 ( Eun-joon Chun )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 10호 발행 연도 : 2021 페이지 : pp. 698-708 (11 pages)

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The metallurgical aspects of weld solidification cracking in Ni-based superalloys (with Ti+Al > 5 mass%) have not been widely investigated thus far. Herein, the solidification cracking susceptibility of the CM247LC superalloy and its welds with ERNiFeCr-2 filler wire was quantitatively evaluated using a novel modified Varestraint testing method, for the successful manufacturing of CM247LC superalloy gas turbine blades. It was found that the solidification brittle temperature range (BTR) of the CM247LC superalloy was 400 K. This measurement was obtained with a high-speed thermo-vision camera. The BTR increased to 486 K for the CM247LC/ERNiFeCr-2 welds (dilution ratio: 74%). Theoretical calculations (i.e., the Scheil equation, performed using Thermo-Calc software) were conducted to determine the temperature range in which both solid and liquid phases coexist, together with the microstructural characterization of the solidification cracking surfaces. The greater increase in BTR for the CM247LC/ERNiFeCr-2 welds than that for CM247LC was attributed to the enlargement of the solid-liquid coexistence temperature range. This correlated with the formation of a low-temperature Laves phase during the terminal stage of solidification, and was affected by the diluted Nb and Fe components in the ERNiFeCr-2 filler metal. Based on the experimental and theoretical results, the proposed modified Varestraint testing method for dissimilar welds is expected to be an effective testing process for solidification cracking behavior in the manufacturing of high-soundness CM247LC superalloy welds.
(Received June 24 2021; Accepted July 16, 2021)

KCI등재 SCI SCOPUS

4수소 분위기에서 Mg와 VCl3의 밀링에 의한 Mg의 수소 흡수 방출 특성의 향상

저자 : 송명엽 ( Myoung Youp Song ) , 이성호 ( Seong Ho Lee ) , 곽영준 ( Young Jun Kwak )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 10호 발행 연도 : 2021 페이지 : pp. 709-717 (9 pages)

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VCl3 (vanadium (III) chloride) was selected as an additive to Mg to increase the hydrogenation and dehydrogenation rates and the hydrogen storage capacity of Mg. Instead of MgH2, Mg was used as a starting material since Mg is cheaper than MgH2. Samples with a composition of 95 wt% Mg + 5 wt% VCl3 (named Mg-5VCl3) were prepared by milling in hydrogen atmosphere (reactive milling). In the first cycle (n=1), Mg-5VCl3 absorbed 5.38 wt% H for 5 min and 5.95 wt% H for 60 min at 573 K in 12 bar hydrogen. The activation of Mg-5VCl3 was completed after three hydrogenation-dehydrogenation cycles. During milling in hydrogen, β-MgH2 and γ-MgH2 were produced. The formed β-MgH2 and γ-MgH2 are considered to have made the effects of reactive milling stronger as β-MgH2 and γ-MgH2 themselves were being pulverized. The introduced defects and the interfaces between the Mg and the phases formed during the reactive milling and during hydrogenation-dehydrogenation cycling are believed to serve as heterogeneous active nucleation sites for MgH2 and Mg-H solid solution. The phases generated during hydrogenation-dehydrognation cycling are also believed to prevent the particles from coalescing during hydrogenation-dehydrognation cycling.
(Received June 13 2021; Accepted July 28, 2021)

KCI등재 SCI SCOPUS

5RF sputtering으로 증착된 ZnO 박막을 전자 수송층으로 사용한 양자점 발광 다이오드에 관한 연구

저자 : 강명석 ( Myoungsuk Kang ) , 김지완 ( Jiwan Kim )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 10호 발행 연도 : 2021 페이지 : pp. 718-723 (6 pages)

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We report a highly efficient quantum dot light emitting diode (QLEDs) with a radio frequency (RF) sputtered ZnO thin film as an electron transport layer (ETL) instead of the conventional ZnO nanoparticles (NPs) by solution process. ZnO NPs have been used as a key material to improve the performance of QLEDs, but the charge imbalance in ZnO NPs resulting from fast electron injection, and their limited uniformity are significant disadvantages. In this study, ZnO layers were deposited by RF sputtering with various O2 partial pressures. All of the ZnO films showed preferential growth along the (002) direction, smooth morphology, and good optical transmittance. To test their feasibility for QLEDs, we fabricated devices with RF sputtered ZnO layers as an ETL, which has the inverted structure of ITO/RF sputtered ZnO/QDs/CBP/MoO3/Al. The optical/electrical characteristics of two devices, comprised of RF sputtered ZnO and ZnO NPs, were compared with each other. QLEDs with the sputtered ZnO ETL achieved a current efficiency of 11.32 cd/A, which was higher than the 8.23 cd/A of the QLEDs with ZnO NPs ETL. Next, to find the optimum ZnO thin film for highly efficient QLEDs, deposition conditions with various O2 partial pressures were tested, and device performance was investigated. The maximum current efficiency was 13.33 cd/A when the ratio of Ar/O2 was 4:3. Additional oxygen gas reduced the O vacancies in the ZnO thin film, which resulted in a decrease in electrical conductivity, thereby improving charge balance in the emission layer of the QLEDs. As a result, we provide a way to control the ZnO ETL properties and to improve device performance by controlling O2 partial pressure.
(Received June 14 2021; Accepted July 9, 2021)

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6Charge Transport and Thermoelectric Properties of Sn-Doped Tetrahedrites Cu12Sb4-ySnyS13

저자 : Hee-jae Ahn , Il-ho Kim

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 10호 발행 연도 : 2021 페이지 : pp. 724-731 (8 pages)

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In this study, tetrahedrite compounds doped with Sn were prepared by mechanical alloying and hot pressing, and their charge transport and thermoelectric properties were analyzed. X-ray diffraction analysis revealed that both the synthetic powders and sintered bodies were synthesized as a single tetrahedrite phase without secondary phases. Densely sintered specimens were obtained with relatively high densities of 99.5%-100.0% of the theoretical density, and the component elements were distributed uniformly. Sn was successfully substituted at the Sb site, and the lattice constant increased from 1.0348 to 1.0364 nm. Positive signs of the Hall and Seebeck coefficients confirmed that the Sn-doped tetrahedrites were p-type semiconductors. The carrier concentration decreased from 1.28 × 1019 to 1.57 × 1018 cm-3 as the Sn content decreased because excess electrons were supplied by doping with Sn4+ at the Sb3+ site of the tetrahedrite. The Seebeck coefficient increased with increasing Sn content, and Cu12Sb3.6Sn0.4S13 exhibited maximum values of 238-270 μVK-1 at temperatures of 323-723 K. However, the electrical conductivity decreased as the amount of Sn doping increased. Thus, Cu12Sb3.9Sn0.1S13 exhibited the highest electrical conductivity of (2.24-2.40) × 104 Sm-1 at temperatures of 323-723 K. A maximum power factor of 0.73 mWm-1K-2 was achieved at 723 K for Cu12Sb3.9Sn0.1S13. Sn substitution reduced both the electronic and lattice thermal conductivities. The lowest thermal conductivity of 0.49-0.60Wm-1K-1 was obtained at temperatures of 323-723 K for Cu12Sb3.6Sn0.4S13, where the lattice thermal conductivity was dominant at 0.49-0.57 Wm-1K-1. As a result, a maximum dimensionless figure of merit of 0.66 was achieved at 723 K for Cu12Sb3.9Sn0.1S13.
(Received July 12, 2021; Accepted July 28, 2021)

KCI등재 SCI SCOPUS

7Glycothermally Synthesized Self-aggregated ZnS Spherical Particles for Methyl Orange Photodecomposition

저자 : Sang-jun Park , Jeong-hwan Song

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 10호 발행 연도 : 2021 페이지 : pp. 732-740 (9 pages)

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Using ethylene glycol (C2H6O2) as the solvent, ZnS particles were synthesized in high yield at a relatively low temperature of 125 ℃ via the glycothermal method. We report a facile method for preparing spherical self-aggregated ZnS particles from ZnS nanocrystals, using zinc acetate as the Zn2+ source and thiourea as a sulfur source, without mineralization or other agents. The crystal phase structure, morphology, size, surface chemical composition, and optical properties of the self-aggregated ZnS particles were characterized using XRD, FE-SEM, TEM, XPS, BET, and UV-Vis absorption. The ZnS particles had a cubic phase zinc blende structure without any other impurities. The average crystallite size of the synthesized primary nanocrystal, estimated from XRD peak width and TEM images, was nearly 4 nm. FE-SEM images showed that all of the ZnS consisted of self-aggregated particles with a spherical morphology and a size of approximately 0.2 μm~0.5 μm, and contained many tiny primary nanocrystals. The prepared ZnS exhibited strong photoabsorption in the UV region. The optical band gap decreased from 3.85 eV to 3.62 eV as the glycothermal reaction temperature was increased, due to improvement in particle size and crystallization. The effects of the glycothermal reaction temperature on the photocatalytic activity of the synthesized self-aggregated ZnS particles were investigated by the photodecomposition of methyl orange (MO) dye under UV illumination (λ = 365 nm). The prepared ZnS exhibited excellent photocatalytic degradation with increasing reaction temperature, of 125 ℃ (5%), 150 ℃ (10%), 175 ℃ (60%), and 200 ℃ (90%) after irradiation for 60 min. It was found that the ZnS particle prepared at 200 ℃ achieved the highest photocatalytic degradation, with nearly 100% MO decomposition after 90 min, by various photogenerated radical scavengers.
(Received June 9 2021; Accepted July 6, 2021)

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8고분자 전해질 연료전지의 산소환원반응에 대한 Pt-M 합금 촉매의 최근 연구 동향

저자 : 심유진 ( Yu-jin Shim ) , 정원석 ( Won Suk Jung )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 10호 발행 연도 : 2021 페이지 : pp. 741-752 (12 pages)

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Due to environmental pollution and global warming, research on new energy sources that can replace fossil fuels is important. A fuel cell is an eco-friendly energy conversion system that discharges water, and uses hydrogen as fuel. Although platinum is a widely used catalyst in PEMFCs, it has commercial limitations because of its low stability and high cost. Pt-based bimetal catalysts are being studied to improve performance and reduce the cost of fuel cell catalysts. Pt-M is excellent in terms of performance, stability, and cost, avoiding the disadvantages of the Pt catalyst. Studies on various bimetallic catalysts have been conducted, and among them, studies on Pt-Ni, Pt-Co, and Pt-Fe have been the most active. This review summarizes reports of fuel cell catalysts using Pt-M from 2014 to 2020. In recent studies, in order to improve the Pt-M performance, there have been attempts to change the pretreatment, the type of support, and the composition of Pt and M. There have also been studies that have applied new synthetic methods, which are different from traditional synthetic methods. Many Pt-M catalysts have shown better performance than commercial Pt/C, and exhibited stable performance in durability tests.
(Received May 29 2021; Accepted July 7, 2021)

KCI등재 SCI SCOPUS

9질소 5N 가스 분위기에서 다공질 ZrFe 합금의 산화 안정화

저자 : 김광배 ( Kwangbae Kim ) , 진새라 ( Saera Jin ) , 임예솔 ( Yesol Lim ) , 이현준 ( Hyunjun Lee ) , 김성훈 ( Seonghoon Kim ) , 노윤영 ( Yunyoung Noh ) , 송오성 ( Ohsung Song )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 10호 발행 연도 : 2021 페이지 : pp. 753-759 (7 pages)

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A porous ZrFe alloy specimen was prepared as a 6 × 3 mm (diameter × thickness) disk. The reaction of the ZrFe alloy was confirmed while the whole system was maintained at a target temperature, which was increased from 150 ℃ to 950 ℃ in a 99.999% low purity nitrogen atmosphere, consisting of 10 ppm of impurity gas. Surface color, pore size, stabilized layer, and phase change were confirmed with optical microscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Micro-Raman, according to temperature. The surface color of the ZrFe alloy changed from metallic silver to dark gray as the temperature increased. In the EDS and XPS results, nitrogen component was not observed, and oxygen content increased on each surface at the elevated temperatures. In this way, the ZrFe alloy was stabilized in a low purity nitrogen atmosphere, preventing rapid nitride reactions.
(Received June 1 2021; Accepted July 16, 2021)

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1스핀 코팅법에 의한 Sb2S3 광흡수층 박막의 기계적 거동

저자 : 장마오 ( Mao Zhang ) , 유다영 ( Dayoung Yoo ) , 전영선 ( Youngseon Jeon ) , 이동윤 ( Dongyun Lee )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 1호 발행 연도 : 2021 페이지 : pp. 1-7 (7 pages)

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To measure the mechanical properties of Sb2S3, a two-component compound semiconductor used in the light absorption layer of a solar cell, Sb2S3 thin films were formed on FTO glass using the spin coating method. The spin-coated Sb2S3 thin films were heat-treated at 200 ℃ in an Ar atmosphere for up to 1 hour to form a thin film with continuous crystalline structures. A nanoindentation system was used to measure the mechanical properties of the spin-coated Sb2S3 thin films, and the phenomena appearing during indentation were analyzed. We used the continuous stiffness measurement (CSM) technique, and Young's modulus and hardness measured with the indentation depth of 250 nm were about 53.1 GPa and 1.43 GPa, respectively. The results were analyzed and compared with literature values, which varied from 40 GPa for the nanowire forms of Sb2S3 to 117 GPa, based upon simulation results. Since there are few studies on the mechanical properties of spin-coated Sb2S3 thin films, the results of this study are worthwhile. Besides, we observed that the Sb2S3 thin film had a little brittleness in the indentation test at higher load, and the microstructure was pushed around the indenter depending on the degree of bonding to the FTO glass substrate. This is a matter to be considered when making flexible devices in the future.
(Received September 23, 2020; Accepted October 20, 2020)

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2Zr-1.5Nb-0.4Sn-0.2Fe-0.1Cr 지르코늄 합금 압연 판재의 동적 변형시효 거동

저자 : 김일현 ( Il-hyun Kim ) , 이명호 ( Myung-ho Lee ) , 정양일 ( Yang-il Jung ) , 김현길 ( Hyun-gil Kim ) , 장재일 ( Jae-il Jang )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 1호 발행 연도 : 2021 페이지 : pp. 8-13 (6 pages)

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The behavior of dynamic strain aging (DSA) in a Zr-1.5Nb-0.4Sn-0.2Fe-0.1Cr alloy strip was investigated at temperature ranges of 25-600 °C via a tensile test. The tensile test was performed at two different strain rates 8.33 × 10-5 and 1.67 × 10-2 s-1. The shear stress of the alloy strip revealed a linear dependency on the test temperature when the specimens were tested under a higher strain rate (1.67 × 10-2 s-1). However, the linear relationship was broken due to DSA when the samples were deformed under a lower strain rate (8.33 × 10-5 s-1). The discrepancy was most significant at 400 °C. The trend in DSA behavior was similar irrespective of the orientation of the samples, i.e., rolling direction (RD) or transverse direction (TD). However, the effect of DSA was larger in the TD samples than the RD samples. The phenomena were interpreted to the variation in work hardening exponents and strain rate sensitivity. The value of the exponent decreased from 0.14 to 0.08 along a RD and from 0.1 to 0.07 along a TD, respectively. However, the smallest value was observed at 400-500 °C irrespective of the specimen orientation, which is consistent with the DSA behavior. It is suggested that the DSA was caused by an interaction of moving dislocations with solute atoms typically oxygen.
(Received October 19, 2020; Accepted November 12, 2020)

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3소결기 장입을 위한 미분광브리켓 제조에 대한 연구

저자 : 배종호 ( Jong-ho Bae ) , 김강민 ( Kang-min Kim ) , 이경욱 ( Kyeong-uk Lee ) , 한정환 ( Jeong-whan Han )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 1호 발행 연도 : 2021 페이지 : pp. 14-20 (7 pages)

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In ironmaking, the optimal size of the iron ore charged into a blast furnace is generally 10-30 mm. Oversized ores, which have a smaller reaction surface area, are crushed, while undersized ores, which decrease permeability, undergo a sizing process before being charged into the blast furnace. Recently, however, iron ore has been micronized, and there is less high-quality iron ore. Also, in accordance with the Paris climate change accord, the Republic of Korea must reduce CO2 gas emissions by about 39% before 2030 to conserve the environment. In response, steelmakers have researched a sinter-briquette complex firing process which employs a method of charging where the raw materials are sintered together with briquettes made of ultra-fine ore. Extra heat is needed to sinter the briquettes. If the briquettes are broken during transporting and charging, the sinter bed permeability decreases, which decreases productivity. In this study, briquettes were made by changing manufacturing conditions such as moisture content, feeding speed, and size, and were simulated by changing the pocket depth in a numerical analysis. Consequently, it was determined that the compressive strength of the briquette was highest when moisture in the briquette was 6 wt%, in proportion to feeding speed and large particle size. Briquette density was in inverse proportion to pocket depth, and when the depth was over 15 mm, the briquette was broken in the pocket.
(Received December 16, 2019; Accepted November 9, 2020)

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4인장강도 600 MPa급 저탄소강 필렛 용접부의 저온균열과 미세조직에 따른 수소취성 민감성 및 수소확산 거동

저자 : 안형진 ( Hyoungjin An ) , 이정훈 ( Junghoon Lee ) , 박한지 ( Hanji Park ) , 유재석 ( Jaeseok Yoo ) , 정성욱 ( Sungwook Chung ) , 박종민 ( Jongmin Park ) , 강남현 ( Namhyun Kang )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 1호 발행 연도 : 2021 페이지 : pp. 21-32 (12 pages)

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Hydrogen flowing into a weld causes hydrogen embrittlement (HE), so to prevent cold cracks in the weld, HE must be suppressed. In this study, single-pass fillet weldments were fabricated using two different welding fillers with the same strength level as the American Welding Society standard. The specimen F-HNi, which had a high, reversible hydrogen content, exhibited cold cracking in the fillet weld. The HE sensitivity index (HE index) was calculated using the in-situ slow strain rate test (SSRT). The reversible hydrogen trap concentration (Crev) and hydrogen diffusion coefficient (Deff) were calculated using the permeation test. The formation of low-temperature transformation phases such as bainite and martensite increased the Crev and decreased the Deff, thereby increasing the HE index. In addition, it was determined that reversible hydrogen was most effectively trapped in the low-temperature transformation phase, as confirmed by silver decoration. We concluded that the cold cracks in the F-HNi specimen were associated with the large Crev, small Deff, and large HE index. HE sensitivity can be controlled by optimizing the microstructure, even when welding fillers with the same level of strength are used. To reduce HE sensitivity, it is important to reduce the number of reversible hydrogen trap sites, by reducing the fraction of the low-temperature transformation phase where the reversible hydrogen trapping most occurs.
(Received November 23, 2020; Accepted December 4, 2020)

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5Top submerged lance 로의 스파이스산물 중 구리의 황산 침출에 대한 납과 안티몬의 영향

저자 : 채수진 ( Sujin Chae ) , 유경근 ( Kyoungkeun Yoo ) , Richard Diaz Alorro , Manis Kumar Jha

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 1호 발행 연도 : 2021 페이지 : pp. 33-40 (8 pages)

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Cu-Pb and Cu-Sb alloys were prepared at various ratios, from 10:90 to 90:10, and leaching tests with sulfuric acid were conducted to investigate the effect of Pb and Sb on the leaching of Cu from speiss, which is obtained from the top submerged lance furnace process. The Cu leaching efficiency increased as the amount of Cu increased in both alloys, but the leaching efficiencies were lower in the Cu-Sb alloy than in the Cu-Pb alloy. For example, in alloys with 70% Pb and Sb ratio, the leaching efficiency of Cu from the Cu-Pb alloy increased to 95%. The leaching efficiency of the Cu-Sb alloy was 67% in 2 mol/L sulfuric acid solution with 1% pulp density and 1000 cc/min O2 at 90 °C, 400 rpm, and 6 hours. When the leaching residues were examined with SEM (scanning electron microscopy)-EDS (Energy-dispersive X-ray spectroscopy), it was found that in all Cu-Pb alloys, Cu and Pb exist as independent metal phases, while, in Cu-Sb alloys, Cu formed intermetallic compounds with Sb such as Cu2Sb, because the Cu-Sb alloy has a lower melting point than the Cu-Pb alloy. These results suggest that Sb may retard the leaching rate of Cu from the alloy. When the leaching residue of speiss obtained from a top submerged lance furnace, intermetallic alloys of Cu-Sb were also observed, having a net structure. The net structure contains Cu metal in the center of the speiss particle, while the intermetallic alloys of Cu-Sb were present in the outer layer of the particle, in good agreement with the results using the alloys in this study. This suggests the intermetallic alloys of Cu-Sb can prevent copper from leaching.
(Received August 21, 2020; Accepted November 9, 2020)

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6수소 기반 환원 제철 공정과 전환 기술

저자 : 이상호 ( Sang-ho Yi ) , 이운재 ( Woon-jae Lee ) , 이영석 ( Young-seok Lee ) , 김완호 ( Wan-ho Kim )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 1호 발행 연도 : 2021 페이지 : pp. 41-53 (13 pages)

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This study analyzed the current state of technical development of the BF-based process, to determine ways to reduce carbon consumption. The technical features of the hydrogen reduction ironmaking process were also examined as a decarbonized ironmaking method, and related issues that should be considered when converting to hydrogen reduction are discussed. The coal rate consumed by the reduction reaction in the coal-based BF process should be less than 50%. The heat requirement for indirect reduction in hydrogen reduction is higher than that of CO reduction, since hydrogen reduction is endothermic. The BF-based integrated steel mill is an energy independent process, since coal is used for the reduction of iron ore and melting, and the by-product gases evolved from the BF process are utilized for reheating the furnace, the power plant, and steam production. For hydrogen reduction, only green hydrogen should be used for the reduction of iron ore, and the power required to melt the iron and for the downstream rolling process will have to be provided from the external grid. Therefore, to convert to hydrogen reduction, green power should be supplied from an external infrastructure system of the steel industry. It will be necessary to discuss an optimized pathway for the step-by-step replacement of current coal-based facilities, and to reach agreement on the socio-economic industrial transition to hydrogen reduction steel.
(Received September 14, 2020; Accepted November 16, 2020)

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7페르미 면 형상제어에 따른 Bi-Sb-Te 이론 전자수송 특성 변화

저자 : 김상일 ( Sang-il Kim ) , 임종찬 ( Jong-chan Lim ) , 양희선 ( Heesun Yang ) , 김현식 ( Hyun-sik Kim )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 1호 발행 연도 : 2021 페이지 : pp. 54-60 (7 pages)

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Using thermoelectric refrigerators can address climate change because they do not utilize harmful greenhouse gases as refrigerants. To compete with current vapor compression cycle refrigerators, the thermoelectric performance of materials needs to be improved. However, improving thermoelectric performance is challenging because of the trade-off relationship between the Seebeck coefficient and electrical conductivity. Here, we demonstrate that decreasing conductivity effective mass by engineering the shape of the Fermi surface pocket (non-parabolicity factor) can decouple electrical conductivity from the Seebeck coefficient. The effect of engineering the non-parabolicity factor was shown by calculating the electronic transport properties of a state-of-the-art Bi-Sb-Te ingot via two-band model with varying non-parabolicity. The power factor (the product of the Seebeck coefficient squared and electrical conductivity) was calculated to be improved because of enhanced electrical conductivity, with an approximately constant Seebeck coefficient, using a non-parabolicity factor other than unity. Engineering the non-parabolicity factor to achieve lighter conductivity effective mass can improve the electronic transport properties of thermoelectric materials because it only improves electrical conductivity without decreasing the Seebeck coefficient (which is directly proportional to the band mass of a single Fermi surface pocket and not to the conductivity effective mass). Theoretically, it is demonstrated that a thermoelectric figure-of-merit zT higher than 1.3 can be achieved with a Bi-Sb-Te ingot if the non-parabolicity factor is engineered to be 0.2. Engineering the non-parabolicity factor is another effective band engineering approach, similar to band convergence, to achieve an effective improvement in power factor.
(Received October 7, 2020; Accepted November 14, 2020)

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8A New Fracture Analysis Technique for Charpy Impact Test Using Image Processing

저자 : Tae Chang Park , Beom Suk Kim , Ji Hee Son , Yeong Koo Yeo

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 1호 발행 연도 : 2021 페이지 : pp. 61-66 (6 pages)

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The Charpy impact test is used to identify the transition between ductility and brittleness. The percentages of ductile and brittle fractures in steel can be evaluated based on each fracture area, which is presently determined by an analyzer with the naked eye. This method may lead to subjective judgement, and difficulty accurately quantifying the percentage. To resolve this problem, a new analysis method based on image processing is proposed in this study. A program that can automatically calculate the percentage of the ductile and brittle fractures has been developed. The analysis is performed after converting an RGB fracture image into a binary image using image processing techniques. The final binary image consists of 0 and 1 pixels. The parts with the pixel values of 1 correspond to the brittle fracture areas, and the pixel values of 0 represent the ductile fracture areas. As a result, by counting the number of 0 pixels in the entire area, it is possible to automatically calculate the percentage of ductile fracture. Using the proposed automatic fracture analysis program, it is possible to selectively distinguish only the brittle fracture from the entire fracture area, and to accurately and quantitatively calculate the percentages of ductile and brittle fractures.
(Received June 22, 2020; Accepted October 12, 2020)

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9ZrO2 전자전달층 두께에 따른 우레아 첨가 페로브스카이트 태양전지의 물성

저자 : 김광배 ( Kwangbae Kim ) , 송오성 ( Ohsung Song )

발행기관 : 대한금속재료학회 간행물 : 대한금속재료학회지 59권 1호 발행 연도 : 2021 페이지 : pp. 67-72 (6 pages)

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The properties of 6 mM urea added perovskite solar cells (PSCs) according to ZrO2 electron transport layer (ETL) thicknesses of 204, 221, 254, and 281 nm were examined. A solar simulator was used to characterize the photovoltaic properties of the cell. Optical microscopy and field emission scanning electron microscope were used for the microstructure analysis, and a 3D profiler was used to analyze surface roughness. UV-VIS-NIR was used to analyze transmittance. From the photovoltaic analysis result, an energy conversion efficiency (ECE) of 14.93% was exhibited by the cell with a 221 nm-ZrO2 layer and added urea. From the analysis result of microstructure and surface roughness, 384 nm grain size was obtained through appropriate surface roughness of base layer for perovskite growth and the grain size coarsening by the urea under the 221 nm-ZrO2 condition. For this reason, ECE increased as the resistance of the grain boundary decreased. When the thickness of the ETL was increased above 250 nm-ZrO2, the ECE decreased due to the reduction in light transmittance, and light reaching the perovskite layer. Therefore, the ECE of PCS could be enhanced by selecting a ZrO2 layer with the appropriate thickness and the addition of urea.
(Received October 12, 2020; Accepted December 5, 2020)

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