• 제목/요약/키워드: $\gamma$',$\gamma$"and $\delta$precipitate

검색결과 5건 처리시간 0.018초

Al-Li-Cu-Mg-Zr 합금에 있어서 δ'상 조대화를 위한 Lithium의 확산계수 평가 (The Evaluation of Diffusivity of Lithium for Coarsening of δ' Precipitate in AI-Li-Cu-Mg-Zr Alloy)

  • 정동석;김은호;조현기
    • 열처리공학회지
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    • 제7권1호
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    • pp.17-24
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    • 1994
  • The evaluation and analysis of diffusivity of lithium for coarsening and coarsening kinetics of ${\delta}^{\prime}$ precipitate in Al-Li-Cu-Mg-Zr alloy aged at $170^{\circ}C$ have been investigated by transmission electron microscopy. With ageing time, ${\delta}^{\prime}$ precipitate coaesened to followed $\bar{\gamma}{\propto}t^{1/3}$ and coarsening kinetics was found to be obeyed to the Lifshitz-Slyozov-Wagner(LSW) theory and diffusivity of lithium for coarsening of ${\delta}^{\prime}$ precipitate in Al-Li-Cu-Mg-Zr alloy was obtained to be $5.85{\times}10^{-17}{\sim}1.53{\times}10^{-16}$ by experimental coarsening rate constant and various coarsening kinetic theory. Diffusivity of lithium measured by using various model but MLSW and Tsumuraya (VI) et al. model in Al-Li-Cu-Mg-Zr alloy is similar to that calculated by the Costas's diffusivity equation. It was, therefore, suggested that additing to the Cu, Mg and Zr element in Al-Li system have no great effect on diiffusivity of lithium for coarsening of ${\delta}^{\prime}$ This suggest that in matrix.

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INCONEL 718 초내열 합금의 열처리에 따른 미세조직 변화 (Effect of Heat Treatment on the Microstructures of Inconel 718 Superalloy)

  • 최중환;이기룡;조창용;김인배
    • 열처리공학회지
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    • 제5권2호
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    • pp.85-94
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    • 1992
  • Microstructural evolution of wrought Inconel 718 superalloy with different heat treatment conditions was studied. Heat treatment was performed via conventional(CHT), modified(MHT), Merrick(MeHT) and modified Merrick (MMeHT) methods. The size of ${\gamma}^{\prime}$ and ${\gamma}^{\prime\prime}$ precipitates which are principal strengthening phases in Inconel 718 superalloy increase in order of CHT, MHT, MeHT. For the case of MMeHT, a coexistence of fine ${\gamma}^{\prime\prime}$ precipitate and very coarse particles due to exess growth of ${\gamma}^{\prime\prime}$, which is called bimodal distribution, was observed. CHT gave the finest grain size. (Ti, Nb)C carbide and needle-like ${\delta}$ phase were formed together at grain boundaries for CHT, and were formed both inside and at boundaries of grains for MHT, MeHT and MMeHT. Morphology of partially serrated grain boundaries was developed in all heat treatment conditions except CHT.

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주조용 718합금의 고온 인장 성질에 미치는 석출물의 영향 (Effect of Precipitates on the High Temperature Tensile Properties of Cast Alloy 718)

  • 주동원;조창용;김두현;류영수;김인수;조해용;최승주
    • 한국재료학회지
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    • 제10권7호
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    • pp.515-521
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    • 2000
  • 주소용 718합금의 고온 인장 성질에 미치는 석축물의 영향을 상추출법과 미세조직관찰을 통해 고찰되었다. 고온 인장시험에서 $760^{\circ}C$까지는 인장강도와 연신율이 동시에 감소하였고, 그보다 높은 온도에서는 인장강도는 급격히 감소하고 연신율은 증가하였다. 고온 인장시험에의한 응력의 영향으로 인하여 ${\gamma}',{\gamma}"$석출물의 양은 $760^{\circ}C$에서 최대의 값을 나타내었다. 미세한 ${\gamma}',{\gamma}"$상의 석출이 최대로 일어나는 온도에서 석출물에의한 유동응력의 증가로 인해 항복강도의 저하폭이 작았으며, 연신율은 가장 낮은값을 나타내었다. $760^{\circ}C$보다 높은 온도에서는 전체적인 석출물의 양도 감소하였고, 특히 강화석출상의 양이 적어 연화현상이 급격히 나타났다. 급격히 나타났다.

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슈퍼 듀플렉스 스테인리스강의 응고·냉각 시 상석출에 미치는 냉각속도의 영향 (Influence of the Cooling Rate on the Phase Precipitation of Super Duplex Stainless Steel)

  • 장은석;김기영;김석준
    • 한국주조공학회지
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    • 제35권2호
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    • pp.23-28
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    • 2015
  • This work presents the effect of the cooling rate on the precipitation of super duplex stainless steel. Specimens of super duplex stainless steel with a specific composition were cooled at various cooling rates after being melted at $1550^{\circ}C$ in a directional solidification furnace. Ferrite (${\delta}$), Austenite (${\gamma}$), Sigma (${\sigma}$), and Chi (${\chi}$) phases were precipitated when the cooling rate was lower than 0.22 K/s. When the cooling rate was 0.22 K/s or faster, ${\sigma}$ and ${\chi}$ phases were not precipitated.

$Na_2O-Fe2O_3-B_2O_3-P_2O_5$ 계 유리의 도전성에 관한 연구 (A Study on the Electrical Conductivity of $Na_2O-Fe2O_3-B_2O_3-P_2O_5$ System Glass)

  • 박용원;이경태
    • 한국세라믹학회지
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    • 제22권3호
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    • pp.35-40
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    • 1985
  • The composition of the base glass was determined to be $Na_2O$ 15, $Fe_2O_3$ 35, $B_2O_3$ 0~20, $P_2O_5$ 30~50 by mole percent. The heating temperature for nucleation was determined by means of thermal expansion curve. Crystalline phases were investigated by X-ray diffraction method and I.R Spectra. Electrical conductivities of glass spec-imens were observed in the temperature range 25~20$0^{\circ}C$ The activation energies of these specimens were caculated. The results obtained were as follows : 1) The limit composition of the melts 15mol% $Na_2O$ 35mole% $Fe_2O_5$ 20mole% $B_2O_3$ 30mole% $P_2O_5$ was able to be formed into desired shapes during cooling, . 2) In the measurement of d. c conductivity($\delta$) on the glasses in the system $15Na_2O-35Fe_2O_3$-$B_2O_3$-(50-x) $P_2O_5$ the values decreased by replacing 5 mole% $P_2O_5$ with $B_2O_3$ 3) The d. c conducties of heat treated samples were increased by replacing $P_2O_5$ with $B_2O_3$ 4) $B_2O_3$ contributed to precipitate crystals such as${\gamma}$-$Fe_2O_3$ $Fe_3O_4$ which had the advantage of electronic conduction in heat treated samples. 5) The slope plotted Log($\delta$) versus 1/T in this glass system was linear in the measured temperature range.

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