• Progress in Superconductivity
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• v.1 no.2
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• pp.120-124
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• 2000

Ni-13%Cr and Ni-70%Cu alloy tapes were prepared by using high purity metal powders as starting materials. The Ni-13%Cr and the Ni-70%Cu mixtures were isostatically pressed, sintered, rolled and texture-annealed. SEM EDS analysis showed that copper and nickel atoms were completely mixed, while the alloying between the chromium powders and the nickel powders was incomplete. In spite of incomplete alloying between nickel and chromium powders, sharp cube-texture was developed for the Ni-13%Cr tape as well as the Ni-70%Cu tape.

• Journal of Korea Foundry Society
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• v.30 no.4
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• pp.151-156
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• 2010

The high-strength low-alloy (HSLA) steels have low carbon contents (0.05~0.25% C) in order to produce adequate formability and weldability, and they have manganese contents up to 1.7%. Small quantities of silicon, chromium, nickel, copper, aluminum, molybdenum are used in various combinations. The results contained in this paper can provide the valuable information on the development of $-40^{\circ}C$ low temperature HSLA. Furthermore, the present experimental data will provide important database for casting steel materials of the offshore structure.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.1
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• pp.17-21
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• 2001

The effects of Cr content above its solubility limit and thermomechanical treatment on tensile strength and electrical conductivity of Cu-Cr alloys were studied to obtain optimum Cr content exhibiting a high tensile strength without degradation of electrical conductivity. The increase in Cr content above the solubility limit increased tensile strength of Cu-Cr alloys without deterioration of the electrical conductivity. The electrical conductivity was not affected by cold rolling. The electrical conductivity of a Cu-3.5%Cr alloy subjected to cold rolling ${\rightarrow}$ aging treatment ($450^{\circ}C{\times}1hr$) ${\rightarrow}$ cold rolling was equal to that of the alloy subjected to cold rolling ${\rightarrow}$ aging treatment. However, the tensile strength of the alloy subjected to the former thermomechanical treatment was superior to that of the alloy subjected to the latter thermomechanical treatment at all the deformation degrees.

• Journal of the Korean institute of surface engineering
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• v.45 no.6
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• pp.264-271
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• 2012

Due to the good corrosion resistance and machinability, copper alloy is commonly employed for shipbuilding, hydroelectric power and tidal power industries. The Cu alloy, however, has poor durability, and the seawater application at fast flow condition becomes vulnerable to cavitation damage leading to economic loss and risking safety. The HVOF(High Velocity Oxygen Fuel) thermal spray coating with WC-10Co4Cr were therefore introduced as a replacement for chromium or ceramic to minimize the cavitation damage and secure durablility under high-velocity and high-pressure fluid flow. Cavitation test was conducted in seawater at $15^{\circ}C$ and $25^{\circ}C$ with an amplitude of $30{\mu}m$ on HVOF WC-10Co4Cr coatings produced by thermal spray. The cavitation at $15^{\circ}C$ and $25^{\circ}C$ exposed the substrate in 12.5 hours and in 10 hours, respectively. Starting from 5 hours of cavitation, the coating layer continued to show damage by higher than 160% over time when the temperature of seawater was elevated from $15^{\circ}C$ to $25^{\circ}C$. Under cavitation environment, although WC-10Co4Cr has good wear resistance and durability, increase in temperature may accelerate the damage rate of the coating layer mainly due to cavitation damage.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.4
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• pp.426-431
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• 2008

The high-strength low-alloy(HSLA) steels have low carbon contents($0.05{\sim}0.25%$ C) in order to produce adequate formability and weldability, and they have manganese contents up to 1.7%. Small quantities of silicon, chromium, nickel, copper, aluminum, molybdenum are used in various combinations. The results contained in this paper can provide the valuable information on the development of $-40^{\circ}C$ low temperature HSLA. Furthermore, the present experimental data will provide important database for casting steel materials of the offshore structure.

• The Journal of Korean Academy of Prosthodontics
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• v.17 no.1
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• pp.23-34
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• 1979

In this study, the adhesive strength of three commercial polycarboxylate cements to ten types of dental casting alloys, such as gold, palladium, silver, indium, copper, nickel, chromium, and human enamel and dentine were measured and compared with that of a conventional zinc phosphate cement. The $8.0mm{\times}3.0mm$ cylindrical alloy specimens were made by casting. The enamel specimens were prepared from the labial surface of human upper incisor, and the dentine specimens were prepared from the occulusal surface of the human molar respectively. Sound extracted human teeth, which had been kept in a fresh condition since, extraction, were mounted in a wax box with a cold-curing acrylic resin to expose the flattened area. The mounted teeth were then placed in a Specimen Cutter (Technicut) and were cut down under a water spray, and then the flat area on the all specimens were ground by hand with 400 and 600 grit wet silicone carbide paper. Two such specimens were then cemented together face-to-face with freshly mixed cement, and moderate finger pressure was applied to squeeze the cement to a thin and uniform film. All cemented specimens were then kept in a thermostatic humidor cabinet regulated at $23{\pm}2^{\circ}C.$ and more than 95 per cent relative humidity and tested after 24 hours and 1 week. Link chain was attached to each alloy specimen to reduce the rigidity of the jig assembly, and then all the specimens were mounted in the grips of the Instron Universal Testing Machine, and a tensile load was delivered to the adhering surface at a cross head speed of 0.20 mm/min. The loads to which the specimens were subjected were recorded on a chart moving at 0.50 mm/min. The adhesive strength was determined by measuring the load when the specimen separated from the cement block and by dividing the load by the area. The test was performed in a room at $23{\pm}2^{\circ}C.$ and $50{\pm}10$ per cent relative humidity. A minimum of five specimens were tested each material and those which deviated more than 15 per cent from the mean were discarded and new specimens prepared. From the experiments, the following results were obtained. 1) It was found that the adhesive strength of the polycarboxylate cement to all alloys tested was considerably greater than that of the zinc phosphate cement. 2) The adhesive strength of the polycarboxylate cements was superior to the non precious alloys, such as the copper, indium, nickel and chromium alloys, but it was inferior to the precious gold, silver and palladium alloys. 3) Surface treatment of the alloy was found to be an important factor in achieving adhesion. It appears that a polycarboxylate cement will adhere better to a smooth surface than to a rough one. This contrasts with zinc phosphate cements, where a rough helps mechanical interlocking. 4) The adhesion of the polycarboxylate cement with enamel was found superior to its adhesion with dentine.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.1
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• pp.50-55
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• 2021

Copper-chromium alloys have been used as contact materials of vacuum interrupters in circuit breakers, but new materials with highly stable performance are required to break the high voltage and high current barrier due to the recent increase in breaking capacity. In this paper, a new contact material was fabricated from a ternary alloy instead of existing Cu-Cr alloys. Its breaking performance and endurance were verified from a synthetic test and compared with that of various contact materials. The test results verified that the breaking performance of the new contact material was excellent.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.6
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• pp.88-95
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• 2014

Spinning process to inner wall has been applied for reducing the weight of regenerative cooling chamber of liquid propellent rocket engine. The fractures of the blanks of cylinder part and nozzle throat part have been observed during spinning processes. In order to overcome the problem, the mandrel and the blank shape have been modified, and the inner wall was successfully manufactured through the modifications. The manufactured spinning prototype of nozzle throat part was successfully bulged without cracking and necking, and it was confirmed to secure sufficient formability necessary for fabricating thrust chamber.

• Korean Journal of Materials Research
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• v.28 no.6
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• pp.317-323
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• 2018

Crystal structure of the $L1_2$ type $(Al,X)_3Ti$ alloy (X = Cr,Cu) is analyzed by X-ray diffractometry and the nonuniform strain behavior at high temperature is investigated. The lattice constants for the $L1_2$ type $(Al,X)_3Ti$ alloys decrease in the order of the atomic number of the substituted atom X, and the hardness tends to increase. In a compressive test at around 473K for $Al_{67.5}Ti_{25}Cr_{7.5}$, $Al_{65}Ti_{25}Cr_{10}$ and $Al_{62.5}Ti_{25}Cu_{12.5}$ alloys, it is found that the stress-strain curves showed serration, and deformation rate dependence appeared. It is assumed that the generation of serration is due to dynamic strain aging caused by the diffusion of solute atoms. As a result, activation energy of 60-95 kJ/mol is obtained. This process does not require direct involvement. In order to investigate the generation of serrations in detail, compression tests are carried out under various conditions. As a result, in the strain rate range of this experiment, serration is found to occur after 470K at a certain critical strain. The critical strain increases as the strain rate increases at constant temperature, and the critical strain tends to decrease as temperature rises under constant strain rate. This tendency is common to all alloys produced. In the case of this alloy system, the serration at around 473K corresponds to the case in which the dislocation velocity is faster than the diffusion rate of interstitial solute atoms at low temperature.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.3
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• pp.107-113
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• 2005

A calorimeter of 2-ton thrust level rocket engine chamber has been developed to measure the wall heat flux. The liner of the chamber is made of copper-chromium alloy to maximize the heat transfer performance and structural strength. 1-D design code based on empirical correlations has been used for the prediction of the global thermal characteristics while 3-D CFD has been applied for the verification of local cooling performance. The predicted average wall heat flux at the throat is 43 $MW/m^{2}$ for the combustion chamber pressure of 53 bar. The chamber structure is confirmed to be safe at the pressure of 150 bar through 2-D stress analysis and measurement of the strain of the test species. Finally, the test of pressurizing the calorimeter chamber has been performed with water at the pressure of 150 bar in room temperature environment. No thermal damage has been detected after the hot-fire test in the test nozzle of same cooling performance with the developed calorimeter though the measured throat heat flux is higher than the design value by 10%.