• 한국재료학회지
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• 제16권2호
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• pp.137-143
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• 2006

The effects of Cu and Fe additions on the thermal stability, microstructure and mechanical properties of $Al_{85}-Ni_{8.5}-Mm_{6.5},\;Al_{84}-Ni_{8.5}-Mm_{6.5}Cu_1,\;Al_{84}-Ni_{8.5}-M_{m6.5}Fe_1$ alloys, manufactured by gas atomization, degassing and hot-extrusion were investigated. Gas atomization, with a wide super-cooled liquid region, allowed the alloy powders to exhibit varying microstructure depending primarily on the powder size and composition. Al hotextruded alloys consisted of homogeneously-distributed fine-grained fcc-Al matrix and intermetallic compounds. A substitution of 1 at.% Al by Cu increased the thermal stability of the amorphous phase and produced alloy microstructure with smaller fcc-Al grains. On the other hand, the same substitution of 1 at.% Al by Fe decreased the stability of the amorphous phase and produced larger fcc-Al grains. The formation of intermetallic compounds such as $Al_3Ni,\;Al_{11}Ce_3\;and\;Al_{11}La_3$ was suppressed by the addition of Cu or Fe. Among the three alloys examined, the highest Vickers hardness and compressive strength were obtained for $Al_{84}-Ni_{8.5}-M_{m6.5}Cu_1$ alloy, and related to the finest fcc-Al grain size attained from increased thermal stability with Cu addition.

• 한국전기전자재료학회논문지
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• 제20권12호
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• pp.1099-1104
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• 2007

In order to develop non-heated STAl(super thermal resistant Aluminum alloy) for ampacity gain conductor, the systematic research was carried out. Especailly, the effect of a very small amount of Zr, Sc element in EC grade Al ingot on mechanical and electrical properties was our priority. As a result, it was found that the strength and recrystallization temperature of designed alloy was gradually increased with Zr, Sc addition up to 0.3 wt.%. However, the electric conductivity showed no drastic change. The tensile strength and recrystalliztion temperature, $17.75{\sim}20.05\;kgf/mm^2$ and $420{\sim}520\;^{\circ}C$, was obtained at 0.3 wt.% Zr, Sc addition, respectively. Particles of the $Al_3Zr$ and $Al_3Sc$ phase affected the ambient and elevated-temperature strength of the alloys.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.519-520
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• 2007

In order to develop non-heated STAl(super thermal resistant Aluminum alloy) for ampacity gain conductor, the systematic research was carried out. Especially, the effect of a very small amount of Zr element in EC grade Al ingot on mechanical and electrical properties was our priority. As a result, it was found that the strength and recrystallization temperature of designed alloy was gradually increased with Zr addition up to 0.3wt.%. However, the electric conductivity showed no drastic change. The tensile strength and recrystalliztion temperature, $17.75\;kgf/mm^2$ and $420^{\circ}C$, was obtained at 0.3 wt.% Zr addition, respectively.

• 소성∙가공
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• 제32권3호
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• pp.145-152
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• 2023

The Inconel 706 alloy is a nickel-based super alloy and requires a large load for hot forging due to its excellent mechanical properties at high temperature. Rotary forging process is an innovative metal forging process where workpiece is gradually deformed by the revolving conical upper die with an inclination angle. This process allows that the workpiece is partially in contact with an upper die during the process so that the press force is considerably lower compared with the conventional upsetting process. In this study, experiments of rotary forging process and conventional upsetting process for cylindrical parts using Inconel 706 where conducted to investigate the formability of rotary forging process. And microstructure analysis and mechanical properties of Inconel 706 were performed to investigate the effect of rotary forging process on the material property.

• 대한치과기공학회지
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• 제31권3호
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• pp.27-34
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• 2009

This study compared and analyzed changes to the mechanical characteristics to nonprecious metal alloy for porcelain fused to metal crowns when it's repetitively used without the addition of new alloy. Metal samples were made with the Verabond V nonprecious metal alloy. Those samples to measure tensile and yield strength were made in the standardized design(ISO 22674), those to measure bond strength in the $25mm{\times}3mm{\times}0.5mm$ format, and those to measure hardness in the $10mm{\times}10mm{\times}1mm$ format. A ceramic to measure bond strength was made at the center of the metal sample in the length of $8{\ss}{\AE}$ by using Noritaker Super Porcelain EX-3. Ten samples were prepared for one, three and five repetitions of casting each. The test results were as follows: 1. The more casting was repeated, the more significantly tensile strength dropped. 2. The more casting was repeated, the more significantly yield strength dropped. 3. Repetitive casting didn't cause significant changes to bond strength. 4. The Vickers hardness significantly fell with increasing repetitions of casting. There were no changes to bond strength observed with the increasing number of repeating casting. But tensile strength, yield strength, and Vickers hardness decreased. Those results indicate that repeated casting can affect durability and that careful attention should be paid by avoiding repetitive use or excessive increase of uses when no new alloy is added.

• 대한치과보철학회지
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• 제38권2호
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• pp.160-168
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• 2000

This study evaluated the effects of four adhesive metal primers on the shear bond strength of a heat curing denture base resin(Lucitone 199) to cobalt-chromium alloy(Biosil-f). The adhesive metal primers were Cesead Opaque Primer, Metal Primer, MR Bond, and Super-Bond liquid. The metal surface primed or nonprimed was filled with the heat-curing methyl methacrylate resin. The specimens were stored in water at $37^{\circ}C$ for 24 hours and the alternately immersed in water bath at $5^{\circ}C\;and\;55^{\circ}C$ for up to 2,000 thermal cycles. Shear bond strengths were measured using UTM at a crosshead speed of 0.5mm/min. Failure surface were examined under magnifying glasses. All the primers examined improved the shear bond strength between denture base resin and cobalt-chromium alloy compared with nonprimed specimens before thermal cycling. The bond strength of Cesead Opaque Primer was greatest. And after 2,000 thermal cycles, the bond strengths between resin and cobalt-chromium alloy were decreased but the difference between thermal cycling 0 and 2,000 at Cesead Opaque primer and Metal Primer were not significant. This study indicated that Cesead Opaque Primer & Metal Primer is effective primers to obtain higher bond strength between heat cured denture base resin and cobalt-chromium alloy.

• 한국정보통신학회논문지
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• 제20권8호
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• pp.1546-1552
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• 2016

일반적으로 치과용 주조기는 불때를 이용하여 합금을 용해하기 때문에 합금의 적절한 용융온도 및 주조시간을 조절하기 어렵고 이로 인해 가스공이나 핀홀과 같은 주조결함을 발생시키며 과열로 인한 보철물의 결함을 보이고 있다. 또한 합금이 용융된 후 주조 시 대부분 투시창이나 비접촉식 온도센서를 부착하여 적절한 주조온도가 되면 작업자가 원심력을 발생하는 버튼을 눌러 도가니에 용융된 합금을 주조링에 주입한다. 이러한 결과로 대부분 주조온도가 너무 높거나 낮아서 주조결함을 많이 발생하고 있으며 균일한 주조체를 얻지 못하고 있는 실정이다. 본 논문에서는 외부의 비접촉식 온도 센서를 이용한 온도계측이 아닌 실제 합금의 사용 온도를 계측할 수 있는 단일 온도센서를 이용한 치과용 고주파 주조기를 개발하였다.

• 한국주조공학회지
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• 제33권5호
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• pp.215-225
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• 2013

The alloys required for fossil power plants are altered from stainless steel that has been used below $600^{\circ}C$ to Ni-based alloys that can operate at $700^{\circ}C$ for Hyper Super Critical (HSC) steam turbine. The IN740 alloy (Special Metals Co. USA) is proposed for improved rupture strength and corrosion resistance at high temperature. However, previous studies with experiments and simulations on stable phases at about $700^{\circ}C$ indicated the formation of the eta phase with the wasting of a gamma prime phase, which is the most important reinforced phase in precipitation hardened Ni alloys, and this resulted in the formation of precipitation free zones to decrease the strength. On the basis of thermodynamic calculation, the new Ni-based superalloy named LESS 1 (Low Eta Sigma Superalloy) was designed in this study to improve the strengthening effect and structure stability by depressing the formation of topologically close packed phases, especially sigma and eta phases at high temperature. A thermal exposure test was carried out to determine the microstructure stability of LESS 1 in comparison with IN740 at $800^{\circ}C$ for 300 hrs. The experimental results show that a needle-shaped eta phase was formed in the grin boundary and it grew to intragrain, and a precipitation free zone was also observed in IN740, but these defects were entirely controlled in LESS 1.

• 한국산학기술학회논문지
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• 제19권8호
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• pp.403-409
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• 2018

고온 부품 소재로 사용하는 니켈계 내열합금인 Inconel 713C에는 Ni 70 %, Cr 12 %, Al 6 % 및 Mo 4% 등의 유가금속을 함유되어 있다. 이중 유가금속에서 경제적 가치를 가지는 원소는 Mo이므로 회수하여 재활용하여야 한다. 본 연구는 폐 인코넬계(Inconel 713C) 모의 내열합금 침출액으로부터 액-액 추출법(용매추출법 및 역추출법)을 이용하여 Mo을 분리 회수하였다. 회수된 수상을 증발 건조 및 열처리법을 이용하여 Mo 화합물을 제조하였다. 수상은 $NaMoO_4$ $2H_2O$을 증류수에 용해하여 사용하였으며, 추출제로는 음이온추출제인 Alamine 336과 양이온추출제인 Cyanex 272, 희석제로는 등유(Kerosene) 사용하였고, 음이온추출제인 Alamine 336 1 %이상에서 99 % 이상의 추출률을 확인하였다. 역추출제로는 황산, 염산 및 질산을 사용하였고, 각각 농도가 증가할수록 탈거율이 증가하였으며, 질산의 경우 4 M에서 96 %의 탈거율을 나타냈었다. 용매추출과 역추출에서 얻은 Mo 함유 수상을 증발 건조하여 순도 97.5 %의 $MoO_3$를 제조하였다. 본 연구를 통해 Mo이 함유된 순환자원으로부터 Mo을 효율적으로 회수하면 국내의 자원효율성과 자원수요의 공급경쟁력을 향상시킬 수 있다.

• 자원리싸이클링
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• 제24권5호
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• pp.56-62
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• 2015

폐 초내열합금으로부터 침출된 염산용액에서 레늄을 회수하기 위하여 용매추출법을 이용한 레늄의 분리연구를 수행하였다. 용매추출공정을 통해 수상은 레늄이 용해된 합성용액을 사용하고 추출제의 종류 및 농도, 수상의 pH, HCl의 농도, 불순물의 영향을 조사하는 연구를 진행하였다. 레늄의 원료로 Ammonium perrhenate ((APR), Aldrich, $NH_4ReO_4$)을 사용하였고, 수상에 존재하는 레늄을 유기상으로 추출하기 위해 추출제는 음이온추출제인 Alamine304-1, 양이온추출제인 Cyanex272과 $D_2EHPA$를 사용하였다. 음이온추출제인 Alamine304-1 사용시 레늄의 추출율이 99% 이상 나타났으며 수상의 pH 는 0-2 사이에서 99% 추출되었다. Alamine304-1의 농도를 0.1, 0.5, 1 및 2%으로 조절하여 추출실험한 결과, 농도가 증가함에 따라 추출율이 증가한다. 레늄용액에 알루미늄, 코발트, 바나듐을 첨가하여 용매추출법에 의해 분리 실험한 결과 레늄은 99.8 %으로 추출되었으나 기타 금속들은 거의 추출되지 않았다.