• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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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.

• Journal of Korea Foundry Society
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• v.15 no.4
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• pp.416-421
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• 1995

Recently Al-Cu-P alloys are used to refine primary Si of hypereutectic Al-Si alloys. Because it has inside AlP compound that acts as nucleation site in the melt, Al-Cu-P alloy has good refinement effect in lower holding temperature and after shoter holding times. In this study Al-Cu-P refinement agent was made by mechanical alloying method. When Al-13.5wt%Cu-1.5wt%P was alloyed mechanically for 30hr in Ar atmosphere by high energy ball mill, it had the refinement effect that showed primary Si size of about $30{\mu}m$ in Al-20wt%Si at $760^{\circ}C$, treated for 15min.

• Journal of Korea Foundry Society
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• v.15 no.5
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• pp.449-458
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• 1995

• Journal of Korea Foundry Society
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• v.17 no.4
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• pp.347-355
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• 1997

It is well known that the coarse primary Si in hypereutectic Al-Si alloys deteriorate castability, machinability, and mechanical properties. So, many treatment has been tried to refine the primary Si increasing cooling rate and adding refinement agent. Therefore. the purpose of our work was the observation of the effect on the refinement of primary Si and the analysis of the trend to apply to the casting process by changing the amount of P addition and the cooling rate while fixing the temperature at $750^{\circ}C$ of P addition and the type of AlCuP. In the condition of amount of P addition was fixed, primary Si was finer as cooling rate increased but in case of cooling rate was fixed, the effect of refinement was resisted as incersed the amount of P addition. At a relatively slow cooling rate of $22^{\circ}C/sec$, refinement was governed by the amount of P addition rather than cooling rate. At elevated cooling rate of $51^{\circ}C/sec$ and $99^{\circ}C/sec$, the undercooling due to faster cooling rate promoted nucleation of primary Si rather than P addition more significantly.

• Journal of Korea Foundry Society
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• v.22 no.5
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• pp.257-264
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• 2002

Effects of Ca content on the refinement of primary Si of Aluminum B390 alloy have been examined. Ca was found to have an effect on the refinement of primary Si particle. Primary Si particle size has been refined as Ca content of the melts decreased and cooling rate increased. A control of Ca content by the addition of $CuCl_2$ to the melt was the most efficient in the refinement of primary Si particles. The minimum size of primary Si particles in this study was $15.0\;{\mu}m$ when a residual content of Ca element in the alloy was 5ppm, Primary Si particle size was refined as primary Si crystallization temperature increased, which was attributed to the decrease of Ca content in the melts.

• Journal of Korea Foundry Society
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• v.23 no.2
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• pp.63-68
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• 2003

Al-Ti-C grain refiner form a relatively new alternative to the existing class of Al-Ti-B type grain refiners for achieving fine equiaxed structures in aluminum alloys during casting and solidification. The present study was carried out to investigate the influence of Al-Ti-C master alloys on the grain structure of Al-7Si alloys. The present study also investigates the relationship between grain refining efficiency and concentrations of Fe and Si in hypo-eutectic Al-Si alloys using Al-3Ti-0.13C master alloys. It is found that several parameters affect significantly the grain refining performance in silumin alloys. The present study reports the influence of various parameters such as alloy content, master alloy addition level, melt holding time and superheat on the grain refining efficiency in Al-7Si alloys.

• Journal of Korea Foundry Society
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• v.35 no.5
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• pp.120-127
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• 2015

The effects of Ti, B and Zr on grain refinement and castability were investigated in Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurement of cooling curve and micro-structure observation were performed to analyze the effects of the addition of minor elements Ti, B and Zr during solidification. The prominence of effect on grain refinement was in increasing order for Ti, Zr and B element. Fine grain size and an increase of the crystallization temperature for ${\alpha}$-Al solution were evident as the amount of addition elements increased in this study. Addition of 0.15wt% Ti was most effective for grain refinement, and the resulting grain size of ${\alpha}$-Al solution for shell mold and steel mold were $72.3{\mu}m$ and $23.5{\mu}m$, respectively. Fluidity and shrinkage tests were perform to evaluate the castability of the alloy. Maximum fluidity length and minimum ratio of micro shrinkage were recorded for 0.15wt% Ti addition due to the effect of the finest grain size.

• Journal of Korea Foundry Society
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• v.16 no.6
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• pp.537-549
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• 1996

This study aims at investigating the correlation of microstructure and mechanical properties of the AZ91 Mg/Al borate whisker composites fabricated by squeeze csting technique with a variation of applied pressure. Microstructure observation and in-situ fracture tests were conducted on the composites to identify the microfracture process. Detailed microstructural analyses indicated that the grain refinement could be achieved with applied pressure and the little change in volume fraction on reinforcing whiskers could be carried out. It was also found clearly from in-situ observation of crack initiation and propagation that in the composite processed by the lower applied pressure, microcracks were initiated earily at whisker/matrix interfaces, thereby resulting in the drop in strength. In the composite processed by the higher applied pressure, on the other hand, planar slip lines were well developed in the matrix, and then propagated through whiskers without whisker/matrix decohesion. Thus, the effect of the applied pressure on microstructure and mechanical properties can be explained by grain refinement, increased amounts of reinforcements, and improvement of whisker/matrix interfacial strength as the applied pressure in increased.

• Journal of the Korean Society for Heat Treatment
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• v.29 no.6
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• pp.259-263
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• 2016

This study was carried out to investigate the effect of hot forging ratio on the microstructure and mechanical properties of incoloy 825 alloy. Hot forging was carried out at the forging ratio of 0%, 60% and 90% respectively in a range of $900^{\circ}C{\sim}1,140^{\circ}C$ and followed solution treatment was conducted at $1,000^{\circ}C$ for 1 hr. In all the specimens of hot forged of 0%, 60% and 90%, precipitates were not observed. The average grain size of 0% specimen is $82{\mu}m$ and that of 60% and 90% is $56{\mu}m$ and $31{\mu}m$, respectively. The range of grain size in the 0% specimen is uneven in $182{\mu}m$ to $31{\mu}m$, but the grain size of 90% specimen is uniform. With increasing hot forging ratio, the mechanical properties such as tensile strength, elongation, hardness increased and impact toughness increased by grain refinement.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.3
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• pp.156-159
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• 2011