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  • Title/Summary/Keyword: Microstructure development

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Effect of Alloying Element Addition on the Microstructure, Tensile and Impact Toughness of the Modified Al-6.5Si Alloy (개량 Al-6.5Si 합금의 미세조직, 인장 및 충격 인성에 미치는 합금 원소 첨가의 영향)

  • Park, T.H.;Baek, M.S.;Yoon, S.I.;Kim, J.P.;Lee, K.A.
    • Transactions of Materials Processing
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    • v.29 no.3
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    • pp.135-143
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    • 2020
  • Low-cost alloying elements were added to a modified Al-6.5Si alloy and its microstructure, tensile and impact toughness properties were investigated. The alloying elements added were Mg, Zn, and Cu, and two kinds of alloy A (Mg:0.5, Zn:1, Cu:1.5 wt.%) and alloy B (Mg:2, Zn:1.5, Cu:2 wt.%) were prepared. In the as-cast Al-6.5Si alloys, Si phases were distributed at the dendrite interfaces, and Al2Cu, Mg2Si, Al6 (Fe,Mn) and Al5 (Fe,Mn)Si precipitates were also observed. The size and fraction of casting defects were measured to be higher for alloy A than for alloy B. The secondary dendrite arm spacing of alloy B was finer than that of alloy A. It was confirmed by the JMatPro S/W that the cooling rate of alloy B could be more rapid than alloy A. The alloy B had higher hardness and strength compared to the values of alloy A. However, the alloy A showed better impact toughness than alloy B. Based on the above results, the deformation mechanism of Al-6.5Si alloy and the improving method for mechanical properties were also discussed.

Effect of Final Annealing Temperature on Microstructure and Creep Characteristics of Nb-containing Zirconium Alloys (Nb 첨가 Zr 합금의 미세조직과 Creep 특성에 미치는 마지막 열처리 온도의 영향)

  • Park, Yong-Gwon;Yun, Yeong-Gwon;Wi, Myeong-Yong;Kim, Taek-Su;Jeong, Yong-Hwan
    • Korean Journal of Materials Research
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    • v.11 no.10
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    • pp.879-888
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    • 2001
  • The effects of final annealing temperature on the microstructure and creep characteristics were investigated for the Zr-lNb-0.2X (X=0, Mo, Cu) and Zr-lNb- 1Sn-0.3Fe-0.1X (X=0, Mo, Cu) alloys. The microstructures were observed by using TEM/EDS, and grain size and distributions of precipitates were analyzed using a image analyzer. The creep test was performed at 400C under applied stress of 150 MPa for 10 days. The β-Zr was observed at annealing temperature above 600C. In the temperature above600C, the grain sizes of both alloy systems appeared to be increased with increasing the final annealing temperature. The creep strengths of Zr-1Nb-1Sn-0.3Fe-0.1X alloys were higher than those of Zr-1Nb-0.2X ones due to the effect of solid solution hardening by Sn in Zr-lNb-lSn-0.3Fe-0.1X alloy system. Also, Mo addition showed the strong effect of precipitate hardening in both alloy systems. The creep strength rapidly decreased with increasing the annealing temperature up to 600C. However, a superior creep resistance was obtained in the sample that annealed to have a second phase of β-Zr. It was considered that the appearance of β-Zr would play an important role in the strengthening mechanism of creep deformation.

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Effect of Alloying Elements on the Microstructure and Texture of the Secondary Ingots made by Al Used Beverage Cans (알루미늄 폐캔을 이용한 2차지금의 미세조직 및 집합조직에 미치는 합금원소의 영향)

  • 박차용;고흥석;강석봉
    • Resources Recycling
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    • v.9 no.2
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    • pp.46-52
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    • 2000
  • Aluminum can to can recycling was divided into two stpes. The first step was composed of the processes such as collection of used beverage cans (UBC), shredding, magnetic separation, De-laquiring, melting and casting. The second one was remelting and casting, heat treating, hot and cold rolling, annealing, and can making. In this study, the effect of alloying elements on the microstructure and texture of the secondary ingots made by Al UBC was investigated. In aluminum can to can recycling, the second phase particles appeared in the solidification stage must be controlled by heat treatment. The optimum heat treatment condition was 615C for 5hrs. the texture in hot rolled sheet was depressed with increasing Mn content, on the other hand, Si and Fe elements promoted the texture development. The textures of can-body sheet should be controlled in the hot rolling and annealing stage because can was formed from cold rolled sheet without heat treatment.

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Fabrication and characterizations of the BSCCO-2212/SrSO4 bulk superconductors (BSCCO-2212/SrSO4 벌크 초전도체의 제작 및 특성평가)

  • Kim, Kyu-Tae;Jang, Seok-Hern;Park, Eui-Cheol;Hwang, Su-Min;Joo, Jin-Ho;Hong, Gye-Won;Kim, Chan-Joong;Kim, He-Lim;Hyun, Ok-Bae
    • Progress in Superconductivity
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    • v.8 no.1
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    • pp.108-112
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    • 2006
  • We fabricated Bi-2212/SrSO4 bulk superconductors by the casting process and evaluated the effects of the powder mixing method and annealing temperature on the texture, microstructure, and critical current. In the process, the Bi-2212 powders were mixed with SrSO4 by hand-mixing(HM) and planetary ball milling(PBM) method and then the powder mixtures were melted at 1100C1200C, solidified, and annealed. We observed that the rod made by the PBM had a more homogeneous microstructure and smaller SrSO4 and second phases than that of the rod made by the HM, resulting in increased Ic. The Ic of the rod also depended on the annealing temperature and the highest Ic was obtained to be 200 A when prepared by HM at 1200C and annealed at 810C which is probably due to the moderate density and 2212 texture and the smaller and less second phase compared to that at higher temperature. The possible causes of the variations of Ic with the powder mixing method and annealing temperature were related to the microstructural evolution based on the SEM, EPMA, and DTA analyses.

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Effects of Alloying Elements on the Properties of High Strength and High Thermal Conductivity Al-Zn-Mg-Fe Alloy for Die Casting (다이캐스팅용 Al-Zn-Mg-Fe 합금의 특성에 미치는 Zn 및 Mg 첨가의 영향)

  • Kim, Ki-Tae;Lim, Young-Suk;Shin, Je-Sik;Ko, Se-Hyun;Kim, Jeong-Min
    • Journal of Korea Foundry Society
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    • v.33 no.4
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    • pp.171-180
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    • 2013
  • The effects of alloying elements on the solidification characteristics, microstructure, thermal conductivity, and tensile strength of Al-Zn-Mg-Fe alloys were investigated for the development of high strength and high thermal conductivity aluminium alloy for die casting. The amounts of Zn and Mg in Al-Zn-Mg-Fe alloys had little effect on the liquidus/solidus temperature, the latent heat for solidification, the energy release for solidification and the fluidity of Al-Zn-Mg-Fe alloys. Thermo-physical modelling of Al-Zn-Mg-Fe alloys by the JMatPro program showed MgZn2, AlCuMgZn and Al3Fe phases in the microstructure of the alloys. Increased amounts of Mg in Al-Zn-Mg-Fe alloys resulted in phase transformation, such as $MgZn_2{\Rightarrow}MgZn_2+AlCuMgZn{\Rightarrow}AlCuMgZn$ in the microstructure of the alloys. Increased amounts of Zn and Mg in Al-Zn-Mg-Fe alloys resulted in a gradual reduction of the thermal conductivity of the alloys. Increased amounts of Zn and Mg in Al-Zn-Mg-Fe alloys had little effect on the tensile strength of the alloys.

Characterization of Microstructure and Thermal property of Ash Deposits on Fire-side Boiler Tube

  • Bang, Jung Won;Lee, Yoon-Joo;Shin, Dong-Geun;Kim, Younghee;Kim, Soo-Ryong;Baek, Chul-Seoung;Kwon, Woo-Teck
    • Journal of the Korean Ceramic Society
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    • v.53 no.6
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    • pp.659-664
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    • 2016
  • Ash deposition of heat exchange boiler, caused mainly by accumulation of particulate matter, reduces heat transfer of the boiler system. Heat and mass transfer through porous media such as ash deposits mainly depend on the microstructure of deposited ash. Therefore, in this study, we investigated microstructural and thermal properties of the ash deposited on the boiler tube. Samples for this research were obtained from the fuel economizer tube in an industrial waste incinerator. To characterize microstructures of the ash deposit samples, scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD) and BET analysis were employed. The results revealed that it had a porous structure with small particles mostly of less than a few micrometers; the contents of Ca and S were 19.3, 22.6% and 18.5, 18.7%, respectively. Also, the results showed that it consisted mainly of anhydrite (CaSO4) crystals. - The thermal conductivities of the ash deposit sample obtained from the economizer tube in industrial waste incinerator were measured to be 0.63 and 0.54 W/mK at 200C, which were about 100 times less than the thermal conductivity (61.32 W/mK) of the boiler tube itself, indicating that ash deposition on the boiler tube was closely related to a decrease in boiler heat transfer.

A Study on Microstructure and Mechanical Properties of IF Steel Cube Fabricated by Multi-Axial Diagonal Forging Ver.1 and Ver.2 Processes (다축대각단조(MADF) Ver.1 및 Ver.2 공정으로 가공한 IF Steel의 미세조직 및 기계적 성질에 대한 연구)

  • Jeong, D.H.;Jo, Y.Y.;Kwon, S.C.;Kim, S.T.;Lee, S.;Choi, S.H.;Jeong, H.T.
    • Transactions of Materials Processing
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    • v.30 no.6
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    • pp.306-310
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    • 2021
  • In this study, IF steel, which has a body-centered cubic (BCC) crystal structure, was fabricated as a 25 mm-long cube, and then processed for one cycle without intermediate heat treatment by applying MADF Ver.1 and Ver.2 processes. MADF processing was performed with graphite lubrication for each pass at room temperature. The development of the microstructure and texture was analyzed and compared by the location of the specimen using EBSD measurements of the IF steel. Vickers hardness test and miniature tensile test were also performed to analyze the mechanical properties. The coarse grain size of 742.6 ㎛ of the as-received IF steel was refined to a grain size of 53.0 ㎛ after one cycle of MADF Ver.1 processing and 27.0 ㎛ after MADF Ver.2 processing. Vicker's hardness of the as-received IF steel at 94 Hv was increased to 185.6 Hv and 191.2 Hv after one cycle of MADF Ver.1 and Ver.2 processing, respectively.

A Study on the Microstructure and Anisotropic Mechanical Properties of Oxygen-Free Copper Fabricated by Equal Channel Angular Pressing (ECAP공법으로 제조된 무산소동의 미세조직 및 기계적 성질 이방성에 대한 고찰)

  • Lee, Jaekun;Hong, Younggon;Kim, Hyoungseop;Park, Sunghyuk
    • Journal of the Korea Institute of Military Science and Technology
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    • v.22 no.4
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    • pp.492-500
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    • 2019
  • Equal channel angular pressing(ECAP) is a severe plastic deformation technique capable of introducing large shear strain in bulk metal materials. However, if an ECAPed material has an inhomogeneous microstructure and anisotropic mechanical properties, this material is difficult to apply as structural components subjected to multi-axial stress during use. In this study, extruded oxygen-free copper(OFC) rods with a large diameter of 42 mm are extruded through ECAP by route Bc up to 12 passes. The variations in the microstructure, hardness, tensile properties, and microstructural and mechanical homogeneity of the ECAPed samples are systematically analyzed. High-strength OFC rods with a homogeneous and equiaxed-ultrafine grain structure are obtained by the repeated application of ECAP up to 8 and 12 passes. ECAPed samples with 4 and 8 passes exhibit much smaller differences in terms of the average grain sizes on the cross-sectional area and the tensile strengths along the axial and circumferential directions, as compared to the samples with 1 and 2 passes. Therefore, it is considered that the OFC materials, which are fabricated via the ECAP process with pass numbers of a multiple of 4, are suitable to be applied as high-strength structural parts used under multi-axial stress conditions.

Effects of the Content of MgO Additive and Sintering Temperature on the Densification of Alumina Insulator (인슐레이터용 알루미나의 치밀화에 미치는 MgO의 함량과 소결 온도의 영향)

  • Ri Joo Kim;Han Gyeol Jeong;Ye Ji Son;Sang Ki Ko;Hyun Seon Hong
    • Journal of Powder Materials
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    • v.30 no.3
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    • pp.249-254
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    • 2023
  • The influence of MgO addition on the densification and microstructure of alumina (Al2O3) was studied. Compacted alumina specimens were manufactured using ball-milling and one-directional pressing followed by sintering at temperatures below 1700℃. Relative density, shrinkage, hardness, and microstructure were investigated using analytical tools such as FE-SEM, EDS, and XRD. When the MgO was added up to 5.0 wt% and sintered at 1500℃ and 1600℃, the relative density exhibited an average value of 97% or more at both temperatures. The maximum density of 99.2% was with the addition of 0.5 wt% MgO at 1500℃. Meanwhile, the specimens showed significantly lower density values when sintered at 1400℃ than at 1500℃ and 1600℃ owing to the relatively low sintering temperature. The hardness and shrinkage data also showed a similar trend in the change in density, implying that the addition of approximately 0.5 wt% MgO can promote the densification of Al2O3. Studying the microstructure confirmed the uniformity of the sintered alumina. These results can be used as basic compositional data for the development of MgO-containing alumina as high-dielectric insulators.

A study on Mechanical and Fatigue Properties of Spheroidal Graphite Cast Iron (구상흑연주철의 기계적 성질및 피로특성에 관한 연구)

  • Park, No-Gwang;Kim, Chang-Ju;Jun, Eui-Jin
    • 한국기계연구소 소보
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    • s.9
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    • pp.83-93
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    • 1982
  • The influence of different heat treatment conditions on microstructure, mechanical and fatigue properties of Spheroidal Graphite cast Iron with 0.4-0.6% Mn was investigated. 1) Maximum tensile strength was arrived by tempering at about 450Cafter quenching. Tempering at higher than 600C was changed martensitic structure to ferritic structure and secondary graphites were precipitated. 2) The relationship between matrix hardness and total hardness of the specimens are as following. [HB]T=0.7[HB] [HB]M+35 Maximum tensile strength was arrived at the total hardness of HB400-450. 3) Endurance ratio decreases with increasing total hardness, and fatigue limits can be presumed from as following. \sigmaf=\sigmat

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