• Title/Summary/Keyword: Cu matrix effect

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Effect of Austempering Temperatures on the Fractures Characteristic of Grey Cast Iron (오스템퍼링 처리한 회주철의 파괴특성에 미치는 오스템퍼링 온도의 영향에 관한 연구)

  • Kim, Chang-Gyu;Lee, Sung-Yul;Choi, Chang-Ock
    • Journal of Korea Foundry Society
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    • v.12 no.6
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    • pp.442-449
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    • 1992
  • Grey cast iron containing a small amount of Cu and Mo to improve the effect of heat treatment and microstructure were cast and them austenitized. After austenitizing the specimens of castings were austempered at 250$^{\circ}C$, 300$^{\circ}C$ and 350$^{\circ}C$. The effects of matrix structures on mechanical properties and fracture characteristics at the different austempering temperature were investigated. Tensile strength, hardness and impact toughness of austempered grey cast iron showed maximum valve 359 MPa, 321 HB, 3.9 CVN respectively at the lowest austempering temperature, 250$^{\circ}C$. $K_{IC}$ of gref cast iron at a austempering temperature, 250$^{\circ}C$, showed maximum 44 MPa.$m^{1/2}$ even though the amount of retained austenite in it is only 16%. This mainly comes from the refinement of the retained austenite. Quasi-cleavage pattern with a little fit of fibrous pattern was shown on the fractured surface of austempered grey cast iron at all of the temperatures tested.

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A Study on Wetting Behaviors of Al-Coated $SiC_f$ Composite (Al-$SiC_f$ 복합재료에서 보강재의 coating처리가 젖음성에 미치는 영향)

  • Kim, Kyun-Young;Lee, Kyung-Ku;Choi, Dap-Chun;Lee, Doh-Jae
    • Journal of Korea Foundry Society
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    • v.14 no.3
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    • pp.274-284
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    • 1994
  • SiC fibers were coated with Cu, Ag and Ni metallic thin films by magnetron sputtering in order to improve wetting properties between Al matrix and SiC fiber. The wetting behavior of metal coated SiC fiber by pure Al has been studied at $670^{\circ}C{\sim}900^{\circ}C$ range for $10{\sim}90min$. under vacuum atmosphere. Besides, the effect of coated film thickness on the wettability has been investigated. The wetting behavior and interfacial reaction between Al and SiC fibers were analysed with optical microscope and SEM (scanning electron microscope). The wetting behavior of the as-received SiC fiber with Al melt was not uniform, indicated by the contact angles from less than $90^{\circ} to more Al melt was appeared in the initial stage of reation. It was considered that the metallic thin film played an important role in reducing the interfacial free energy and breaking down the aluminum oxide film by eutectic reaction with Al melt. However the wettability of Ni coated SiC fiber was not improved as much as that of Cu or Ag coated SiC fiber. The improvement of wettability by coating thickness is clearly showed in $1{\mu}m$ coated SiC fiber compared with $0.25{\mu}m$ coated SiC.

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The superconductivity and pinning properties of Y2O3-doped GdBa2Cu3O7-δ films prepared by pulsed laser deposition

  • Oh, Won-Jae;Park, Insung;Yoo, Sang-Im
    • Progress in Superconductivity and Cryogenics
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    • v.20 no.4
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    • pp.41-45
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    • 2018
  • We have investigated the effect of $Y_2O_3$ nanoparticles on the pinning properties of $Y_2O_3$-doped $GdBa_2Cu_3O_{7-{\delta}}$ (GdBCO) films. Both undoped and $Y_2O_3$-doped GdBCO films were grown on $CeO_2$-buffered MgO (100) single crystal substrates by pulsed laser deposition (PLD) using KrF (${\lambda}=248nm$) laser. The $Y_2O_3$ doping contents were controlled up to ~ 2.5 area% by varying the internal angles of $Y_2O_3$ sectors put on the top surface of GdBCO target. Compared with the $Gd_2O_3$-doped GdBCO films previously reported by our group [1], the $Y_2O_3$-doped GdBCO films exhibited less severe critical temperature ($T_c$) drop and thus slightly enhanced critical current densities ($J_c$) and pinning force densities ($F_p$) at 65 K for the applied field parallel to the c-axis of the GdBCO matrix (B//c) with increasing the doping content. Below 40 K, the in-field $J_c$ and $F_p$ values of all $Y_2O_3$-doped GdBCO films exhibited higher than those of undoped GdBCO film, suggesting that $Y_2O_3$ inclusions might act as effective pinning centers.

Effect of T6 and T73 Heat Treatments on Microstructure, Mechanical Responses and High Cycle Fatigue Properties of AA7075 Alloy Modified with Mg and Al2Ca ((Mg + Al2Ca)로 개량된 AA7075 합금의 미세조직, 기계적 특성, 그리고 고주기 피로 특성에 미치는 T6 및 T73 열처리의 효과)

  • Hwang, Y.J.;Kim, G.Y.;Kim, K.S.;Kim, Shae K.;Yoon, Y.O.;Lee, K.A.
    • Transactions of Materials Processing
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    • v.30 no.1
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    • pp.5-15
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    • 2021
  • The effects of heat treatments (T6 and T73) on the microstructure, mechanical properties, and high cycle fatigue behavior of modified AA7075 alloys were investigated. A modified 7075 alloy was manufactured using modified-Mg (Mg-Al2Ca) instead of the conventional element Mg. Based on the microstructure, the average grain size was 4.5 ㎛ (T6) and 5.2 ㎛ (T73). Regardless of heat treatment, the modified AA7075 alloys consisted of Al matrix containing homogeneously distributed Al2CuMg and MgZn2 phases with reduced Fe-intermetallic compound. Room temperature tensile tests showed that the properties of modified 7075-T6 (Y.S.: 622MPa, T.S: 675MPa, elongation: 15.4%) were superior to those of T73 alloy (Y.S.: 492MPa, T.S: 548MPa, elongation: 12.8%). Experimental data show that the fatigue life of T6 was 400 MPa, about 64% of its yield strength. However, the fatigue life of T73 alloy was 330 MPa and 67%. Irrespective of the stress level, all crack initiation points were located on the specimen surface, and no inclusions acting as stress concentrators were seen. Superior mechanical properties and high cycle fatigue behavior of modified AA7075-T6 alloy are attributed to the fine grains and homogeneous distribution of small second phases such as MgZn2 and Al2CuMg, in addition to reduced Fe-intermetallic compounds.

The Effect of Burn-out Temperature and Cooling Rate on the Microstructure and Corrosion Behavior of Dental Casting Gold Alloy (치과용 합금 주조 시의 소환온도와 주조 후 냉각방법이 미세조직과 부식거동에 미치는 영향)

  • Lee, Sang-Hyeok;Ham, Duck-Sun;Kim, Hak-Kwan;Jang, Ju-Woong;Kim, Myung-Ho
    • Journal of Technologic Dentistry
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    • v.22 no.1
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    • pp.69-78
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    • 2000
  • The microstructure and corrosion behavior of commercially dental casting gold alloys were investigated to clarify the effect of burn-out temperature and cooling rate. In the case of water quenching after casting, only the αphase, which is typical dendritic microstructure of golda alloy, was detected. However, the precipitates along the grain boundary were detected only at the slow cooling rate and they increased inversely proportional to the burn-out temperature. This might be due to the time difference which solute atom could diffuse. EPMA and SEM results also demonstrated that the precipitate should be lamellar structure consisted of Ag rich phase(${\alpha}_1$) and Cu rich phase (${\alpha}_2$). In terms of corrosion, the galvanic coupling was formed due to the difference of composition between precipitates and matrix at the slow cooling rate. In the case of water quenching, the critical current density($i_p$) which indicate the degree of corrosion was lowest at $650^{\circ}C$ and below the burnout temperature, $i_p$ increased with it because of the effect of grain boundary segregation. But above the temperature, $i_p$ increased with it. This may be due to the strain field effect by residual thermal stress.

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The Study of Preparation of Block Using Wastewater Sludge of Petrochemical Factory (석유화학공장 폐수슬러지를 이용한 벽돌제조 연구)

  • Hu, Kwan;Lu, Juk-Yong;Wang, Seung-Ho
    • Journal of the Korea Organic Resources Recycling Association
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    • v.11 no.2
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    • pp.66-73
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    • 2003
  • To investigate the availability of solidified wastes as resource, wastewater sludge, waste gypsum and fly ash were mixed and the results with various mixing ratios are as follows. Compressive strength turned out to be increasing as the amount of waste gypsum increases, keeps longer curing inhibition, and higher forming Pressure under the conditions of waste gypsum/sludge ratio 0.31-0.45, and 0.9kg cement as 15% and 1.2kg cement as 20% of total amount. Solidified agent under the fly ash/sludge ratio 0.45, 0.6, compressive strength seemed to be higher than standard one which means solidified wastes with these conditions could be applicable in real life. These results inform that concentrations of the leachate $Cr^{+6}$, Cu, Zn, Cd, Pb solidified matrix, containing low concentration of heavy metal, were cured with/without enough time it still will cause adverse effect on nature environment and application of heavy metal sequester must be needed to reuse industrial wastes from incineration plant solidified matrix. Total cost price, when considering manufacturing capability of the facilities for resourcerizing as 18,000ton was presented 678,664,000 won, as it were, manufacturing cost price was 37,704 won per ton. The results as above has shown that it's possible to use the mixture of waste gypsum/sludge, fly ash/sludge, cement, additions, and solidification matter as substitute of materials like brick, block, interlocking which has proper compressive strength of KS L 5201 and KS F 4004.

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Effect of Co-Culture with Various Somatic Cells during In Vitro Maturation of Immature Oocytes (미성숙 난자의 체외 성숙 시 다양한 체세포의 공동 배양 효과)

  • Yoon, Junchul David;Kim, Eun-Hye;Hwang, Seon-Ung;Cai, Lian;Hyun, Sang-Hwan
    • Journal of Embryo Transfer
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    • v.29 no.1
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    • pp.1-5
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    • 2014
  • Recent 2 decades, including in vitro maturation (IVM), assisted reproductive technologies (ARTs) achieved noteworthy development. However the efficiency of ARTs with in vitro matured oocytes is still lower than that with in vivo oocytes. To overcome those limitations, many researchers attempted to adapt co-culture system during IVM and consequently maturation efficiency has been increased. The beneficial effects of applying co-culture system is contemplated base on communication and interaction between various somatic cells and oocytes, achievement of paracrine factors, and spatial effects of extracellular matrix (ECM) from somatic cell surface. The understanding of co-culture system can provide some information to narrow the gap between in vitro and in vivo. Here we will review current studies about issues for understanding cu-culture system with various somatic cells to improve in vitro maturation microenvironment and provide bird view and strategies for further studies.

A Study on the Gravity Segregation in Monotectic Al Alloys.(I);The Effect of Melting Treatment on the Distribution of Pb, Bi Particles. (Al계 편정합금의 중력 편석에 관한 연구 (I);Pb, Bi 입자의 분산에 미치는 용탕처리의 영향)

  • Hwang, Ho-Eul;Lee, Jai-Ha;Jung, Sung-In;Choe, Jeong-Cheol;Yoon, Eui-Park
    • Journal of Korea Foundry Society
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    • v.10 no.4
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    • pp.316-323
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    • 1990
  • To improve free-cutting property, fine Pb, Bi particles is necessary to be distributed evenly in Al-Cu alloy. The control of added element size and distribution are very difficult because of the insolubility and gravity segregation of Pb, Bi in the matrix. Therefore, in this study, mechanical stirring of the melt, inert gasbubbling, the addition of degasser are used for the fine distribution of Pb, Bi particles. The best distribution are obtained by stirring with 500 rpm for 10min., Ar gas bubbling with 600cc/min for 5min. and degassing with 0.8wt% degasser. As increasing cooling rate, fine grain size and finely dispersed particles were observed. The optimum pouring temperature was $650^{\circ}C$.

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Effects of Inclusions on Fracture Toughness for 1%CrMoV Rotor Steel (1%CrMoV 로터강의 파괴인성에 미치는 개제물의 영향)

  • Jeong, Sun-Eok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.9 s.180
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    • pp.2319-2325
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    • 2000
  • This thesis studied that seven kinds of residual elements(inclusions) had influenced on fracture toughness($K_{IC}$) obtained by Begley-Logsdon and Rolfe-Novak model equation using tensile an d impact test data of I%CrMoV HP(high pressure) rotor steel. $K_{IC}$ design curve of ASME and fracture surface by SEM were also considered, obtained results are summarized as follows $K_{IC}$ was linearly increased with increase of temperature, effect of the inclusions was significantly over FATT. $K_{IC}$ at lower shelf temperature was quantitatively related to yield strength and was agreed well with Begley's equation. It was difficult to determine $K_{IC}$ because of specimen size and tester capacity at upper shelf temperature, but for this view point Rolfe-Novak's equation was useful. The degree of brittle fracture was dependent on FATT fundamentally, adding S, Sb to matrix decreased impact energy and adding Cu, As increased yield(tensile) strength, and the influence of the others minority inclusion was comparatively insignificant.

Nanocomposite Magnetic Materials

  • Ludwig Schultz;Alberto Bollero;Axel Handstein;Dietrich Hinz;Karl-Hartmut Muller;Golden Kumar;Juergen Eckert;Oliver Gutfleisch;Anke Kirehner Aru Yan
    • Journal of Powder Materials
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    • v.9 no.6
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    • pp.381-393
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    • 2002
  • Recent developments in nanocrystalline and nanocomposite rare earth-transition metal magnets are reviewed and emphasis is placed on research work at IFW Dresden. Principal synthesis methods include high energy ball milling, melt spinning, mold casting and hydrogen assisted methods such as reactive milling and hydrogenation-disproportionation-desorption-recombination. These techniques are applied to NdFeB-, PrFeB- and SmCo-type systems with the aim to produce high remanence magnets with high coercivity. Concepts of maximizing the energy density in nanostructured magnets by either inducing a texture via anisotropic HDDR or hot deformation or enhancing the remanence via magnetic exchange coupling are evaluated. With respect to high temperature applications melt spun $Sm(Co_{0.74}Fe_{0.1}Cu_{0.12}Zr_{0.04})_{7.5}$ ribbons were prepared, which showed coercivities of up to 0.53 T at 50$0^{\circ}C$. Partially amorphous $Nd_{60}Fe_xCo_{30-x}Al_{10}(0{\leq}x{\leq}30)$ alloys were prepared by copper mold casting. The effect of transition metal content on the glass-forming ability and the magnetic properties was investigated. The $Nd_{60}Co_{30}Al_{10}$ alloy exhibits an amorphous structure shown by the corresponding diffraction pattern. A small substitution of Co by 2.5 at.% Fe results In the formation of Fe-rich crystallites embedded in the Nd-rich amorphous matrix. The Fe-rich crystallites show hard magnetic behaviour at room temperature with a coercivity value of about 0.4 T, relatively low saturation magnetization and a Curie temperature of 500 K.