• Title, Summary, Keyword: directional solidification

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Solidification Microstructures with Carbon Contents and Solidification Rates in Modified 12Cr-lMo Steels (개량 12Cr-1Mo강에서 탄소 함량 및 응고속도에 따른 응고 조직 형성 거동)

  • Eum C. Y;Lee J. H;Hur S. K;Chi B. H;Ryu S. H
    • Korean Journal of Materials Research
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    • v.14 no.2
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    • pp.101-109
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    • 2004
  • The influences of solidification rates and carbon contents on the formation of the $\delta$-ferrite were studied by directional solidification in modified 12%Cr-l %Mo steels. Directional solidification experimental results showed that solidification microstructure depended on solidification rate and carbon content and chromium equivalent. The length of the mushy zone increased and the dendrite arm spacings decreased as the solidification rate increased. The volume fraction of the 8-ferrite decreased with increasing the solidification rate and carbon content. The volume fraction of the ferrite showed much higher at low solidification rates with planar and cellular interfaces than that at high solidification rates with dendritic interface. It is expected that macro-segregation of C causes lower C content at the lower solidification fraction in the directionally solidified sample, where lower C results in higher volume fraction of the ferrite. In order to estimate solidification microstructure in modified 12Cr-l%Mo steels, various solidification conditions, such as solidification rate, cooling rate, segregation, alloy composition, should be considered.

The Effect of Re addition and Solidification Rate on the Directional Solidification Behavior of Ni-Al Alloy (Ni-Al 합금의 일방향 응고 거동에 미치는 Re 및 응고속도의 영향)

  • Lee, Man-Gil;Yoo, Young-Soo;Jo, Chang-Yong;Lee, Je-Hyun
    • Journal of Korea Foundry Society
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    • v.27 no.6
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    • pp.243-249
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    • 2007
  • The effect of Re addition and solidification rate on the directional solidification behavior of Ni-Al model alloy has been investigated. Directional solidification (DS) were carried out using the modified Bridgman furnace with various solidification rates. The solid/liquid interface during directional solidification was preserved by quenching the specimen after the desired volume fraction of original liquid was solidified. The equilibrium partition coefficients of Al and Re Were estimated by measuring the compositions at the quenched solid/liquid interface. Then, the effect of Re addition on the elemental segregation behavior was carefully analyzed. The differential scanning calorimetry results showed that the Re addition results in increased ${\gamma}'$ solvus and freezing range of the alloy. It was also shown that the primary dendrite arm spacing gradually decreases with increasing the Re content, while the secondary dendrite arm spacing appears to be independent on the Re content. The compositional analyses clearly revealed that the segregation of Al increased with increasing the Re content and solidification rate, while that of Re was found to be independent on the solidification rate in the range of $10{\sim}100{\mu}m/s$ due to its sluggish diffusion rate in the Ni solid solution.

Estimation of Liquid Physical Properties of Mar-M247LC Superalloy by Directional Solidification (일방향 응고법을 이용한 Mar M-247LC 초내열합금의 액상 물성 측정)

  • Kim, Hyeon-Cheol;Lee, Jae-Hyeon;Seo, Seong-Mun;Kim, Du-Hyeon;Jo, Chang-Yong
    • Korean Journal of Materials Research
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    • v.11 no.9
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    • pp.721-726
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    • 2001
  • Directional solidification experiments have been carried out at the solidification rates from 0.5 to 50$\mu\textrm{m}$/s in Mar M-247LC superalloy in which several important liquid properties were estimated by analyzing the interface stability and temperature gradient at the solid/liquid interface. The diffusion coefficient in the liquid was estimated by employing the constitutional supercooling criterion. The temperature gradients changed with solidification rates and latent heat of solidification. The thermal conductivities of solid and liquid could be estimated by heat flux balance at the solid liquid interface.

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Metallurgical Refinement of Multicrystalline Silicon by Directional Solidification (일방향 응고법에 의한 다결정 실리콘의 야금학적 정련)

  • Jang, Eunsu;Park, Dongho;Yu, Tae U;Moon, Byung Moon
    • 한국신재생에너지학회:학술대회논문집
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    • pp.111.1-111.1
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    • 2011
  • The solar energy is dramatically increasing as the alternative energy source and the silicon(Si) solar cell are used the most. In this study, the improved process and equipment for the metallurgical refinement of multicrystalline Si were evaluated for the inexpensive solar cell. The planar plane and columnar dendrite aheadof the liquid-solid interface position caused the superior segregation of impurities from the Si. The solidification rate and thermal gradient determined the shape of dendrite in solidified Si matrix solidified by the directional solidification(DS) method. To simulate this equipment, the commercial software, PROCAST, was used to solve the solidification rate and thermal gradient. Si was vertically solidified by the DS system with Stober process and up-graded metallurgical grade or metallurgical grade Si was used as the feedstock. The inductively coupled plasma mass spectrometry (ICP) was used to measure the concentration of impurities in the refined Si ingot. According to the result of ICP and simulation, the high thermal gradient between the two phases wasable to increase the solidification rate under the identical level of refinement. Also, the separating heating zone equipped with the melting and solidification zone was effective to maintain the high thermal gradient during the solidification.

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A Study of Carbide Thapping and Growth in the Directional Solidification of MAR-M247 LC Super alloy (Ni기 초내열합금의 일방향 응고에서 탄화물의 Trapping과 성장 거동)

  • Lee, Jae-Hyeon;Jin, Geon;Lee, Yong-Tae;Choe, Seung-Ju
    • 연구논문집
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    • pp.95-102
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    • 1996
  • The carbide growth behavior of MAR-M247 LC alloy was investigated by directional solidification and quench method. The carbide volume fraction, trapping and growth behavior were correlated with the growth rate. It was found that the carbide volume fraction decreases at slower growth rate. This decreasing was caused by lower solid-liquid interface trapping ability at the slower growth rate.

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Numerical analysis of steady and transient processes in a directional solidification system

  • Lin, Ting-Kang;Lin, Chung-Hao;Chen, Ching-Yao
    • Coupled systems mechanics
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    • v.5 no.4
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    • pp.341-353
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    • 2016
  • Manufactures of multi-crystalline silicon ingots by means of the directional solidification system (DSS) is important to the solar photovoltaic (PV) cell industry. The quality of the ingots, including the grain size and morphology, is highly related to the shape of the crystal-melt interface during the crystal growth process. We performed numerical simulations to analyze the thermo-fluid field and the shape of the crystal-melt interface both for steady conditions and transient processes. The steady simulations are first validated and then applied to improve the hot zone design in the furnace. The numerical results reveal that, an additional guiding plate weakens the strength of vortex and improves the desired profile of the crystal-melt interface. Based on the steady solutions at an early stage, detailed transient processes of crystal growth can be simulated. Accuracy of the results is supported by comparing the evolutions of crystal heights with the experimental measurements. The excellent agreements demonstrate the applicability of the present numerical methods in simulating a practical and complex system of directional solidification system.

Solidification and Phase Equilibria Studies by Directional Solidification Technique in the Ni-Al System (Ni-Al계에서 일방향응고에 의한 응고 및 상평형 연구)

  • Lee, Jae-Hyeon;Jo, Chang-Yong;Lee, Jong-Hun;Choe, Seung-Ju
    • 연구논문집
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    • pp.163-168
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    • 1995
  • The intermetallic compound $Ni_3Al$ causes a peritectic reaction at the composition and temperature very close to the eutectic reaction in Ni-Al system. Although the phase diagram accepted for this system by ASM Handbook has the eutectic forming between the $\gamma$ and $\gamma$ phases, directional solidification study has shown that the eutectic occurs between $\beta$ and $\gamma$. This work examines the liquidus region using quenched, directional solidification experiments that preserve the microstructrues formed at the solidification front. It is also shown that under certain composition and growth conditions a metastable eutectic between the $\beta$ and $\gamma$ phases forms in this system. Finding of the metastable eutectic provided an important information to understand the phase equilibria near the $Ni_3Al$ composition.

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Austenite Precipitation Behaviors with Solidification Rate and N Solubility in Cast Duplex Stainless Alloys (주조용 이상스테인리스강에서 응고속도 및 질소고용도에 따른 오스테나이트 석출 거동)

  • Lee, Jong-Yeop;Lee, Je-Hyun;Kim, Sang-Sik;Choi, Byung-Hak;Kim, Sung-Jun;Son, Hee-Young
    • Korean Journal of Materials Research
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    • v.17 no.12
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    • pp.654-659
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    • 2007
  • Austenite precipitation behavior was studied with solidification rates and alloying contents, N and Cr, in duplex stainless steels by directional solidification. Directional solidification experiments were carried out with solidification rates, $1{\sim}100mm/s$, and N and Cr contents, $0{\sim}0.27wt.%,\;25{\sim}28wt.%$ respectively, in a duplex stainless steel, CD4MCU. As the solidification rate increases, the dendrite spacing reduced and the austenite phase in the ferrite matrix became finer. The volume fraction of austenite phase increased and its shape went to be round with increasing nitrogen contents in duplex stainless alloys. The Cr alloying element, even though it is a ferrite former, showed to enhance the nitrogen solubility in the alloy and caused the austenite round and finer. Also, Cr was supposed to decrease the austenite volume fraction, but it increased the austenite slightly due to increasing nitrogen solubility during solidification.

Study on High Temperature Phase Transformation and Directional Solidification of TiAl-Nb Alloy (TiAl-Nb 합금의 고온상변태와 일방향응고에 관한 연구)

  • Park, Jong-Moon;Jang, Ho-Seung;Kim, Seong-Woong;Kim, Seung-Eon;Shon, Je-Ha;Oh, Myung-Hoon
    • Journal of the Korean Society for Heat Treatment
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    • v.29 no.5
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    • pp.227-233
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    • 2016
  • Phase transformation phenomenon at high temperature was investigated by using designed TiAl-Nb alloys with addition of the ${\beta}$ stabilizer. Examination of dendritic morphologies in arc-melted button ingot could reveal the crystallography of the primary solidification phase. It was found that the addition of ${\beta}$ stabilizer(Nb) shifted the high temperature region of the binary Ti-Al phase diagram to the high Al composition side so that ${\beta}$ phase forms as a primary crystal even at higher Al composition compared with the binary Ti-Al system. The ${\beta}$ was found to be the primary solidification phase for alloys with Al content less than about 52 at.%. The composition of ${\beta}$ solidification in Ti-Al-Nb ternary system could be determined from the partial liquidus projection which was constructed by observing the microstructure of arc-melted buttons. The Ti-46Al-(6, 8)Nb composition was selected for ${\beta}$ solidification and the directional solidification was performed by a floating zone-type DS apparatus at the growth rate 30 mm/hr respectively.

The Effects of Sample Rotation on Cu-Dendritic Growth During the Directional Solidification of Pb-20wt%Cu Alloy (Pb-20wt%Cu 합금의 일방향 응고시 Cu 수지상 결정성장에 대한 시험편의 회전효과)

  • Kim, Shin-Woo
    • Journal of Korea Foundry Society
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    • v.14 no.6
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    • pp.508-513
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    • 1994
  • For Pb-20wt%Cu alloys, severe macrosegregation due to density difference of the resulting phases in normal directional solidification has been minimized and a uniformly aligned dendritic structure has been produced by axially rotating the sample of 5mm diameter in conjunction with horizontal directional solidification. Under the constant growth velocity of $20{\mu}m/sec$, increasing the rotation rate from 0.18 to 12rpm results in a transition from an aligned columnar to an equiaxed Cu-dendritic structure. With a constant rotation rate of 0.18rpm, increasing the growth velocity from 10 to $50{\mu}m/sec$ also has promoted a transition from columnar to equiaxed structure.

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