• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2001.11a
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• pp.7-7
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• 2001

The increasing interest in light weight materials coupled to the need for cost -effective processing have combined to create a significant opportunity for aluminum P/M. particularly in the automotive industry in order to reduce fuel emissions and improve fuel economy at affordable prices. Additional potential markets for Al PIM parts include hand tools. Where moving parts against gravity represents a challenge; and office machinery, where reciprocating forces are important. Aluminum PIM adds light weight, high compressibility. low sintering temperatures. easy machinability and good corrosion resistance to all advantages of conventional iron bm;ed P/rv1. Current commercial alloys are pre-mixed of either the AI-Si-Mg or AL-Cu-Mg-Si type and contain 1.5% ethylene bis-stearamide as an internal lubricant. The powder is compacted in closed dies at pressure of 200-500Mpa and sintered in nitrogen at temperatures between $580~630^{\circ}C$ in continuous muffle furnace. For some applications no further processing is required. although most applications require one or more secondary operations such as sizing and finishing. These sccondary operations improve the dimension. properties or appearance of the finished part. Aluminum is often considered difficult to sinter because of the presence of a stable surface oxide film. Removal of the oxide in iron and copper based is usually achieved through the use of reducing atmospheres. such as hydrogen or dissociated ammonia. In aluminum. this occurs in the solid st,lte through the partial reduction of the aluminum by magncsium to form spinel. This exposcs the underlying metal and facilitates sintering. It has recently been shown that < 0.2% Mg is all that is required. It is noteworthy that most aluminum pre-mixes contain at least 0.5% Mg. The sintering of aluminum alloys can be further enhanced by selective microalloying. Just 100ppm pf tin chnnges the liquid phase sintering kinetics of the 2xxx alloys to produce a tensile strength of 375Mpa. an increilse of nearly 20% over the unmodified alloy. The ductility is unnffected. A similar but different effect occurs by the addition of 100 ppm of Pb to 7xxx alloys. The lend changes the wetting characteristics of the sintering liquid which serves to increase the tensile strength to 440 Mpa. a 40% increase over unmodified aIloys. Current research is predominantly aimed at the development of metal matrix composites. which have a high specific modulus. good wear resistance and a tailorable coefficient of thermal expnnsion. By controlling particle clustering and by engineering the ceramic/matrix interface in order to enhance sintering. very attractive properties can be achicved in the ns-sintered state. I\t an ils-sintered density ilpproaching 99%. these new experimental alloys hnve a modulus of 130 Gpa and an ultimate tensile strength of 212 Mpa in the T4 temper. In contest. unreinforcecl aluminum has a modulus of just 70 Gpa.

• Journal of Conservation Science
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• v.26 no.2
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• pp.157-169
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• 2010

This study focused on the material characteristics and archaeometric relationship between the molten glass and bronze materials within the crucibles and gilt-bronze Bodhisattva statue excavated from the Ssangbukri site in Buyeo, Korea. Yellowish green to red brown vitreous material in the crucibles was identified as lead glass which contained scarce amount of BaO, and low $Al_2O_3$ and CaO. Metallic molten material was identified as bronze of copper-tin-lead alloy with low amount of impurities that indicated well-refined materials. Also, cassiterite was used for raw metal ore of tin. The Bodhisattva statue consisted of major copper with trace impurities in the core metal, and gold amalgam in the gilded layer. Though lead isotopic analysis showed contradictory results in each lead glass, bronze and Bodhisattva statue that required further examination, it could be stated that the statue was made in the Ssangbukri site based on the high-level technical skills of bronze production.

• 보존과학연구
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• s.27
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• pp.129-143
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• 2006

This report is on a scientific investigation of 3 pairs of 금제태환이식 which were excavated from 황남대총 납분. 태환 is a main part of 태환이식 and it could be classified with 4 types in how to produce, especially how many the golden petal was used. In this investigation, they,3 pairs of 금제태환이식 from 황남대총 남분, were in 3 of 4 types and also I could find that this result was not on the technical progress but on the ingredient of metal. Also, In the result of ingredient assay, I could find that although they were in one pair of 태환 one piece was made in gold and silver alloy and the other piece was made in 99.5 percent of pure Ag with gold amalgam plating. And the another pair was getting red from others because of making in 33percent of Ag and 77 percent of gold, high Ag content. And All pairs of 태환 have a small quantity of Copper. As above, although they are one pair they have the difference of how to produce and the difference of volume and ingredient content, it means that these pairs of 태환 from 황남대총 남분 were made in pressure of time. From now on, if we investigate the ingredient and how to produce of 태환이식 in the local comparative analysis, namely natural science method, we can find out the metal art technique and the social aspect of the ancient times as not analogical inference but scientific basis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.718-723
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• 2016

The use of the scroll compressor in the air conditioning of medium-sized vehicles has increased because of its low torque fluctuation, high energy efficiency and low noise. In addition, the main components of the compressor have been changed from steel to aluminum to reduce its weight, following studies on the constituent materials. The processing precision of the fixed scroll and orbiting involute scroll wrap of the scroll compressor must be below $10{\mu}m$. To ensure this, the surface roughness and contour tolerance are measured. To improve the hardness of the orbiting scrolls using aluminum subjected to anodizing treatment and as the base material, we used a sealing treatment and measured the resulting characteristics. The aluminum materials were made of an Al-Mg-Cu based alloy including small amounts of Ni, Fe, and Zn. The surface roughness was less than $3{\mu}m$ and the processing accuracy was within $10{\mu}m$. Also, the hardness of the nanodiamonds with CNTs used in the sealing treatment was more than 450. This was found to improve the hardness of the material by 50% or more compared to the water sealing treatment and there was little difference between the use of carbon nanotubes and nanodiamonds as sealing materials.

• Korean Journal of Heritage: History & Science
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• v.37
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• pp.267-284
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• 2004

As an initial step to understand the transitions in Korean bronze technology the present study has examined metallurgical microstructures of 8 artifacts excavated from the Silla Wang-Gyong site in Kyongju. Important trends have been found in alloy compositions and also in manufacturing processes. In the design of alloys, the Sn content was apparently changing toward the peritectic point, 22 mass %, of the Cu-Sn phase diagram while the Pb addition was intentionally avoided. This trend in composition was found accompanied by the introduction, subsequent to casting, of such special thermo-mechanical treatments as quenching and forging in artifact manufacture. In addition, the Sn content in alloys containing a significant amount of As was relatively low and no evidence of forging was observed in them. The use of quenching and forging and the rejection of Pb and As from alloys are all necessary requirements if the brittle nature of high Sn alloys is to be overcome in bronze working. This paper will show that the Wang-Gyong era corresponds to that of innovations leading to the technical climax in Korean bronze tradition, which has been maintained up to the present.