• Title/Summary/Keyword: alloying effect

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A Study on the Metal to Zirconia Joining by Applying Direct Current (직류전원부하에 의한 지르코니아와 금속의 접합)

  • Kim Sung Jin;Kim Moon Hyop;Park Sung Bum;Gwon Won Il
    • 한국전기화학회:학술대회논문집
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    • 2005.07a
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    • pp.383-390
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    • 2005
  • Effect of applying a DC voltage on the interfacial reaction at the metal to zirconia interface was investigated utilizing an oxygen ionic conductivity of partially stabilized zirconia. The joining of copper rod and zirconia tube was carried out in Ar gas atmosphere at $1000^{\circ}C$. There are two type of the joining. The one is the reaction bond consisting of copper and zirconia was dominated by surface reaction with a undetectable very thin layer. It was found that copper elements were diffused to zirconia side, but that Zr ions were not diffused to copper side. These results mean application of a DC voltage to migrate oxygen to the copper-zirconia interface can oxidize metal at the copper-zirconia interface and the bonding reaction between zirconia and copper oxide may occur. The other is the reaction bonding was dominated by interdiffusion with a very thick interface layer. This result mean application of a DC voltage can reduce zirconia at the interface. The bonding reaction is to be an alloying between Zr and Cu.

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Fabrication and Mechanical Property of $Al_2$O$_.3$/Al Composite by Pressureless Infiltration (무가압 침윤법에 의한 $Al_2$O$_.3$/Al 복합재료 제조와 기계적 특성)

  • 이동윤;박상환;이동복
    • Journal of the Korean Ceramic Society
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    • v.35 no.3
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    • pp.303-309
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    • 1998
  • The fabrication of Al2O3/Al composite by pressureless infiltration was investigated by the change of Mg and Si content in Al alloy infiltration process and infiltration atmosphere. The effect of alloying elements infiltration atmosphere and interfacial reactants between Al alloy matrix and Al2O3 particles were in-vestigated in terms of bendingstrength and harness test,. The fabrication of Al2O3/Al composite by the vestigated in terms of bending strength and hardness test. The fabrication of Al2O3/Al composite by the pressureless infiltration was done in nitrogen atmosphere with Mg in Al alloy. It was successfully fabricated at $700^{\circ}C$ according to Mg contents in Al alloy and infiltration condition. Because Mg in the Al alloy and ni-trogen atmosphere of infiltratio condition produced Mg-N compound(Mg3N2) it decreased the wetting an-gle between molten Al alloy and Al2O3 particles by coating on surface of Al2O3 particles. The fracture strength of Al2O3/Al-Mg composite was 800MPa and Al2O3/Al-Si-Mg composite was 400MPa. Si in Al alloy decreased the interfacial strength between Al alloy matrix and Al2O3 particles.

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Co-Re-based alloys a new class of material for gas turbine applications at very high temperatures

  • Mukherji, D.;Rosler, J.;Wehrs, J.;Eckerlebe, H.;Gilles, R.
    • Advances in materials Research
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    • v.1 no.3
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    • pp.205-219
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    • 2012
  • Co-Re alloy development is prompted by the search for new materials for future gas turbines which can be used at temperatures considerably higher than the present day single crystal Ni-based superalloys. The Co-Re based alloys are designed to have very high melting range. Although Co-alloys are used in gas turbine applications today, the Co-Re system was never exploited for structural applications and basic knowledge on the system is lacking. The alloy development strategy therefore is based on studying alloying additions on simple model alloy compositions of ternary and quaternary base. Various strengthening possibilities have been explored and precipitation hardening through fine dispersion of MC type carbides was found to be a promising route. In the early stages of the development we are mainly dealing with polycrystalline alloys and therefore the grain boundary embrittlement needed to be addressed and boron addition was considered for improving the ductility. In this paper recent results on the effect of boron on the strength and ductility and the stability of the fine structure of the strengthening TaC precipitates are presented. In the beginning the alloy development strategy is briefly discussed.

Effect of Added B4C on the Mechanical Properties of WC/Ni-Si Hardmetal (WC/Ni-Si 초경합금의 기계적 성질에 미치는 B4C의 영향)

  • Lee, Gil-Geun;Ha, Gook-Hyun
    • Journal of Powder Materials
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    • v.20 no.5
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    • pp.366-370
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    • 2013
  • The effects of $B_4C$ on the mechanical properties of WC/Ni-Si hardmetal were analyzed using sintered bodies comprising WC(70-x wt.%), Ni (28.5 wt.%), Si (1.5 wt.%), and $B_4C$ (x wt.%), where $$0{\leq_-}x{\leq_-}1.2$$ wt.%. Samples were prepared by a combination of mechanical milling and liquid-phase sintering. Phase and microstructure characterizations were conducted using X-ray diffractometry, scanning electron microscopy, and electron probe X-ray micro analysis. The mechanical properties of the sintered bodies were evaluated by measuring their hardness and transverse rupture strength. The addition of $B_4C$ improved the sinterability of the hardmetals. With increasing $B_4C$ content, their hardness increased, but their transverse rupture strength decreased. The changes of sinterability and mechanical properties were attributed to the alloying reaction between $B_4C$ and the binder metal (Ni, Si).

Effect of C-Content for Ti Surface-Alloying Treatment on Steel by $CO_2$ Laser Beam (레이저 빔에 의한 철강재의 Ti 표면합금화에 미치는 C함량의 영향)

  • Choe, Jun-Yeong;Kim, Do-Hun
    • Korean Journal of Materials Research
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    • v.2 no.6
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    • pp.436-442
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    • 1992
  • When $N_2$was used as shielding gas during the formation of Ti surface-alloyed layer by irradiation of $CO_2$laser beam on steel, TiN and F$e_2$Ti were formed regardness of carbon-content in steel. When Ti content was increased in low carbon-content steel, formation of martensitic structure was suppressed due to increase of critical cooling rate for martensitic transformation. In case of high-carbon steel, even though Ti content was about 1.5% in alloyed layer, hardness was increased by formation of martensitic structure instead of ferrite. In addition to that structure, hardness was incrreased further by precipitation of TiC in Ti alloyed-layer of high carbon-steel.

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Effect of Cr on Flow Accelerated Corrosion of Carbon Steel (탄소강의 유동가속부식에 미치는 크롬의 영향)

  • Lee, Eun Hee;Kim, Kyung Mo;Kim, Hong Pyo;Kim, Dong Jin
    • Corrosion Science and Technology
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    • v.14 no.1
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    • pp.25-32
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    • 2015
  • The alloy content of structural materials of nuclear power plants has been recognized an important factor in predicting flow accelerated corrosion (FAC). In particular, many literature data reported that chromium content is one of the most important alloying element and even a small amount of chromium is effective to suppress FAC. This report reviewed and compared chromium models of Ducreux, Bouchacourt, and Kastner which were used in predicting FAC rates. The plant data indicate that Ducreux model may be conservative for the specimen containing 0.15 wt% chromium. The related articles were reviewed as follows. Combined effects of chromium content, pH, temperature, dissolved oxygen (DO), flow velocity, test time, and kinds of amine on the FAC rate were described. 0.1 wt% chromium in steel did not affect the FAC rate with changes in pH. The FAC rates pronounced with higher flow rate and increased with increasing test duration(600 d) for 0.013 wt% chromium. The FAC rates in mixed amine chemistry were higher than in ammonia chemistry, which may be lessened by the addition of chromium to the steel.

Effect of Annealed Oxides on the Formation of Inhibition Layer During Hot-Dip Galvanizing of 590Mpa Trip Steel

  • Kim, Seong-Hwan;Huh, Joo-Youl;Lee, Suk-Kyu;Park, Rho-Bum;Kim, Jong-Sang
    • Corrosion Science and Technology
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    • v.10 no.1
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    • pp.6-12
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    • 2011
  • The selective surface oxidation of a transformation-induced-plasticity (TRIP) steel containing 1.6 wt.% Mn and 1.5 wt.% Si during annealing at $800^{\circ}C$ was investigated for its influence on the formation of an inhibition layer during hot-dip galvanizing. The selective oxidation of the alloying elements and the oxide morphology were significantly influenced by the annealing atmosphere. The pure $N_{2}$ atmosphere with a dew point $-40^{\circ}C$ promoted the selective oxidation of Mn as a crystalline $Mn_{2}SiO_{4}$ phase, whereas the $N_{2}$ + 10% $H_{2}$ atmosphere with the same dew point $-40^{\circ}C$ promoted the selective oxidation of Si as an amorphous Si-rich oxide phase. During hot-dip galvanizing, the $Mn_{2}SiO_{4}$ phase was reduced more readily by Al in the Zn bath than the Si-rich oxide phase. Consequently, the pure $N_{2}$ atmosphere resulted in a higher formation rate of $Fe_{2}Al_{5}$ particles at the Zn/steel interface and better galvanizability than the $N_{2}$ + 10% $H_{2}$ atmosphere.

Fabrication of Sn-Sb Based Powder by Carbothermal Reduction of Spherical Ultrafine Metal Oxides (구형 초미립 금속산화물의 Carbothermal 환원에 의한 Sn-Sb계 분말 합성 및 리튬 이차 전지 음극재료 특성 평가)

  • Hong, Seong-Hyeon;Bae, Jong-Soo;Chin, Young-Mi;Kwon, Hae-Woong
    • Journal of Hydrogen and New Energy
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    • v.17 no.3
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    • pp.324-330
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    • 2006
  • In this study, carbothermal reduction method was employed to synthesis Sn-Sb alloy powders from chief metal oxides with ultrafine sizes. The Sn-Sb powders consisting of ultrafine particles were formed at $800{\sim}900^{\circ}C$ by reduction of oxides. Those powders have high initial discharge capacities ($570{\sim}637\;mAh/g$) and discharge capacities of those powders maintain initial capacity after 20 cycle due to existence of ultrafine particles in powders and alloying effect of Sn-Sb.

Effect of Coating Materials on Surface Layer Structures of Austenitic Stainless Steel Castings in Evaporative Pattern Process (소실모형 주조법에서 도형제가 오스테나이트 스테인레스강 주물의 표면층조직에 미치는 영향)

  • Kim, Ji-Youn;Cho, Nam-Don
    • Journal of Korea Foundry Society
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    • v.15 no.6
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    • pp.604-615
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    • 1995
  • Austenitic stainless steel castings using expandable polystylene(referred to hereafter as EPS) patterns are often affected by distinctive defects associated with incomplete decomposition of the EPS as the molds are filled with metal. The quality of the castings, with particular reference to carbon pick-up in austenitic stainless steel is further influenced to a significant extent by such factors as reduced pressure, the additive by adding $Na_2CO_3$ in coating. The steel composition and microstructure were examined at the surface layer of castings, at depths of 1mm, by taking successive layers of swarf and analysis. In experiments, the carburizing atmosphere was neutralized, showing that the coating performed efficiently by decomposing almost instantly on heating and liberating $CO_2$. The upper parts of castings obtained using EPS patterns were slightly higher in carbon pick-up than other parts. Comparing the 316L and 304 stainless steel castings, qualitative and quantative differences could be found between the carbon pick-up behaviours as influence of the carbon content and alloying elements. Carbide former such as Cr makes carbon more soluble in the steel. This must make carbon pick-up in the surface layer but at the same time richer in carbon especially in the 304 stainless steel castings.

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A Study on the Occurrence of the Striation Defect during the Continuous Casting with the Heated Mold (가열주형 연속주조시 발생되는 줄무늬 결함에 관한 연구)

  • An, Ki-Sung;Song, Tae-Seck;Ji, Tae-Gu;Jo, Hyung-Ho;Kim, Myung-Han
    • Journal of Korea Foundry Society
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    • v.17 no.2
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    • pp.145-150
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    • 1997
  • The striations parallel to the casting direction are the characteristic defects occurring during the unidirectional solidification of nonferrous metals such as pure Al and Sn. It has been known that the defects affect the recrystallization temperature as well as the mechanical and electrical properties of Al. However, it has not been still known about the effect of casting factors such as the casting speed, rod diameter of cast metals, and alloying elements on the occurrence of striations. In the present study, these casting factors affecting the occurrence of striation were investigated by adopting the quantitative examination of striations. Also, the relation between striation defects and feathery grain, which are very similar to the striation defects, was studied.

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