• 한국기계연구소 소보
• /
• 통권17호
• /
• pp.111-123
• /
• 1987

Two dimensional computer simulation of solidification behavior using FDM as simulation tool was applied to AI-bronze casting. By the comparison of computer simulation with the experimental results, it was showed that the final shrinkage position and solidification time are good accordance with results of computer simulation. It is expected that this software will be widely applied to casting design or rise ring for directional solidification.

• 대한금속재료학회지
• /
• 제47권7호
• /
• pp.440-446
• /
• 2009

Co base superalloys have been widely used for the parts of gas turbine due to their excellent strength, thermal fatigue, oxidation resistance and weldability at high temperature. In this study, directional solidifications were carried out at various solidification rates, including $0.5{\sim}300{\mu}m/s$ in the Co base superalloy FSX-414. The cellular interface were formed at a low solidification rate, $1{\mu}m/s$, and the dendritic interface was found at higher solidification rates, $5{\sim}300{\mu}m/s$. As the spacing of dendrite structure decreased, the size and spacing of eutectics decreased. Dendrite arm spacing decreased with increasing solidification rates and temperature gradient. It was interesting to find the $M_{23}C_{6}$ eutectic microstructure formed between $\gamma$ dendrites. Composition analysis showed that Cr and W were segregated severely between the dendrites, which resulted in the formation of Cr-rich $M_{23}C_{6}$ and W-rich MC carbides.

• 열처리공학회지
• /
• 제28권2호
• /
• pp.82-86
• /
• 2015

In this study, the temperature gradient of a floating zone (FZ) apparatus, which is very difficult to directly measure, could be estimated by using the relationships between the lamellar spacing of directionally solidified TiAl alloys and the solidification rate, It was found that the calculated temperature gradient of the FZ apparatus was much higher, and almost ten times higher than that of a Bridgman type directional solidification apparatus.

• 한국결정성장학회지
• /
• 제13권4호
• /
• pp.182-186
• /
• 2003

태양전지의 제조가격의 저가화를 위한 노력이 다각적으로 진행되고 있다. 이중에 하나가 규소 잉곳의 대형화이다. 가로 세로 69cm무게 240kg의 초대형 규소 잉곳을 자동화된 결정성장로를 이용하여 제조하였다. 이 방법은 규소 용체의 열을 하부 흑연 기판을 아래로 이동하면서 축출함으로써 방향성 응고를 유도하고 있다. 이 방법으로 제조된 규소 잉곳을 평가하여 본 결과 전기적, 구조적으로 매우 균일하고 태양전지의 제조에 적합한 것으로 판명되었다.

• 한국주조공학회지
• /
• 제14권1호
• /
• pp.45-51
• /
• 1994

The possibility of using bulk talc as molding material was reviewed and tested with the measurement of thermal properties and computer simulations. The measured thermal conductivity and heat diffusivity($k{\rho}c$) of talc were $2.4W/m^{\circ}C$ and $6.6{\times}10^6J^2/m^4^{\circ}C^2s$, respectively. Thermal properties of talc could be ranked between those of sand mold and iron mold. Talc transforms into cristobalite and enstatite at $910^{\circ}C$, During the transformation volume and structure change, cracks appear on the surface and distortion occurs. Therefore talc can be used for molding material below $910^{\circ}C$ if carefully treated. Computer simulation was carried out to test whether talc insert could promote directional solidification in sand mold and iron mold. In sand mold, it was possible to achieve directional solidification of thin plate casting with the length to thickness ratio of 15, if both iron insert and talc insert were used. In iron mold, it was possible to achieve directional solidification only with talc insert.

• 한국재료학회지
• /
• 제18권11호
• /
• pp.577-582
• /
• 2008

Directional solidification experiments were carried out at $1-300\;{\mu}m/sec$ solidification rates in the single crystal superalloy, CMSX 10. The solid/liquid interface morphology changed from planar to dendritic, and the dendrite spacing became finer as the solidification rate increased. The pool size of the ${\gamma}/{\gamma}'$ eutectic, formed between dendrites, reduced as the solidification rate increased. The phase formation temperatures, such as the solidus, liquidus and eutectic, were estimated by differential scanning calorimetry (DSC) analysis. The morphology of the ${\gamma}/{\gamma}'$ phase, known to be eutectic, showed ${\gamma}'$ cells with a $\gamma$ intercellular network, and this ${\gamma}/{\gamma}'$ was composed of coarse and fine ${\gamma}/{\gamma}'$ regions. In this study, it is suggested that the ${\gamma}/{\gamma}'$ phase was a coupled peritectic.The solidification procedure of the ${\gamma}/{\gamma}'$ between dendrites is also discussed.

• 대한기계학회논문집B
• /
• 제25권4호
• /
• pp.485-495
• /
• 2001

This paper presents a similarity solution for the directional casting of binary peritectic alloys in the presence of shrinkage-induced flow. The present model retains essential ingredients of alloy solidification, such as temperature-solute coupling, macrosegregation, solid-liquid property differences, and finite back diffusion in the primary phase. An algorithm for simultaneously determining the peritectic and liquidus positions is newly developed, which proves to be more efficient and stable than the existing scheme. Sample calculations are performed for both hypo- and hyper-peritectic compositions. The results show that the present analysis is capable of properly resolving the solidification characteristics of peritectic alloys so that it can be used for validating numerical models as a test solution.

• 한국재료학회지
• /
• 제12권12호
• /
• pp.897-903
• /
• 2002

Morphological evolution and growth mechanism at the solid/liquid interface during solidification were investigated in the Ni-base superalloy GTD111M by directional soldification and quenching(DSQ) technique. The experiments were conducted by changing solidification rate(V) and thermal gradient(G) which are major solidification process variables. High thermal gradient condition could be obtained by increasing the furnace temperature and closely attaching the heating and cooling zones in the Bridgeman type furnace. The dendritic/equiaxed transition was found in the G/V value lower than $0.05$\times$10{^3}^{\circ}C$s/$\textrm{mm}^2$, and the planar interface of the MC-${\gamma}$ eutectic was found under $17 $\times$ 10{^3}^{\circ}C$ s/$\textrm{mm}^2$. It was confirmed that the dendrite spacing depended on the cooling rate(GV), and the primary spacing was affected by the thermal gradient more than solidification rate. The dendrite lengths were decreased as increasing the thermal graditne, and the dendrite tip temperature was close to the liquidus temperature at $50 \mu\textrm{m}$/s.

• 한국재료학회지
• /
• 제25권9호
• /
• pp.435-441
• /
• 2015

The ${\gamma}/{\gamma}^{\prime}$ two-phases, commonly known as a eutectic structure, are observed in the ${\gamma}$ interdendritic region of a Ni-base superalloy. However, the growth behavior of the ${\gamma}/{\gamma}^{\prime}$ two-phases, whether it is of eutectic or peritectic nature, has not been decidedly established. Directional solidifications were, thus, performed with the planar interface at a low growth rate of $0.5{\mu}m/s$ in order to promote macro segregation. Directional solidification started with the ${\gamma}$ planar interface and the ${\gamma}^{\prime}$ phase nucleated on the ${\gamma}$ planar interface at the solidification fraction of 0.75. The ${\gamma}/{\gamma}^{\prime}$ two-phases showed the ${\gamma}^{\prime}$ rod structure as major phase and the ${\gamma}$ minor phase between ${\gamma}^{\prime}$ rods, and the volume fraction of the ${\gamma}$ phase changed continuously with an increasing solidification fraction. The two-phase ${\gamma}/{\gamma}^{\prime}$ is seen as the coupled peritectic.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 1999년도 추계학술발표강연 및 논문개요집
• /
• pp.41-41
• /
• 1999