• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.829-830
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• 2006

Recent research at Harbin Institute of Technology on the synthesis of nanocrystalline and untrafine grained materials by mechanical alloying/milling is reviewed. Examples of the materials include aluminum alloy, copper alloy, magnesium-based hydrogen storage material, and $Nd_2Fe_{14}B/{\alpha}-Fe$ magnetic nanocomposite. Details of the processes of mechanical alloying and consolidation of the mechanically alloyed nanocrystalline powder materials are presented. The microstructure characteristics and properties of the synthesized materials are addressed.

• Journal of Powder Materials
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• v.26 no.2
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• pp.112-118
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• 2019

Infiltration is a popular technique used to produce valve seat rings and guides to create dense parts. In order to develop valve seat material with a good thermal conductivity and thermal expansion coefficient, Cu-infiltrated properties of sintered Fe-Co-M(M=Mo,Cr) alloy systems are studied. It is shown that the copper network that forms inside the steel alloy skeleton during infiltration enhances the thermal conductivity and thermal expansion coefficient of the steel alloy composite. The hard phase of the CoMoCr and the network precipitated FeCrC phase are distributed homogeneously as the infiltrated Cu phase increases. The increase in hardness of the alloy composite due to the increase of the Co, Ni, Cr, and Cu contents in Fe matrix by the infiltrated Cu amount increases. Using infiltration, the thermal conductivity and thermal expansion coefficient were increased to 29.5 W/mK and $15.9um/m^{\circ}C$, respectively, for tempered alloy composite.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.5
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• pp.226-231
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• 2020

The Cu-Co-Si alloy shows high strength by forming precipitates by aging precipitation heat treatment of supersaturated solid solution treated with solution treatment such as Cu-Ni-Si alloy, and the Co₂Si precipitated phase is dispersed in the copper matrix. The effect of aging treatment on the microstructure, mechanical and electrical properties of Cu-Co-Si alloys for electronic devices was investigated. As a results of SEM/EDS analysis, it was found that Co₂Si precipitates of 30~300 nm size were distributed in grains. By performing the double aging treatment, it was possible to improve the strength and electrical conductivity by dispersing the fine precipitate evenly.

• Nuclear Engineering and Technology
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• v.24 no.2
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• pp.154-162
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• 1992

Two major goals for chemical cleaning on the secondary side of nuclear steam generators are to remove sludge effectively and to minimize corrosion of base metals. In this work, electrochemical and sludge dissolution behaviors have been investigated in order to find out which parameters are critical and important during a copper removal process for chemical cleaning and to evaluate safety aspects and effectiveness of two major copper removal processes developed commercially in foreign countries. Hydrogen peroxide is vert effective for the process to use EDTA, NH$_4$OH and EDA at 38$^{\circ}C$ to control the potential of copper in a potential range sood for copper sludge removal. Corrosion rates for carbon steel SA 285 Gr.C and Alloy 600 are very small during this process if it is controlled properly. However, the corrosion rate of SA 285 Gr.C will be increased greatly if its corrosion potential is maintained below -450mV. The process to use EDA and ammonium carbonate is effective at 6$0^{\circ}C$ to dissolve copper sludge if the corrosion potential of copper can be controlled above -200mV. However, it is very difficult to raise the corrosion potential of copper to this range by air blowing and stirring.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1083-1090
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• 2012

Copper alloys are widely used for casting materials including ship's propellers and pump impellers as they provide high corrosion resistance. In addition, the demand for these alloys is increasing with rapid growth of offshore structures and exploitation of various substitute energy sources. However, they require regular maintenance because of erosion and cavitation damages induced by exposure to marine environment at high speed flows for a long period of time. Water cavitation peening have received attention as one of surface modifications for durability improvement of the copper alloys. This is a environment friendly technology without influence of heat and easily applicable to casting materials. In this research, water cavitation peening was employed in distilled water for copper alloy castings as a function of time and evaluation of corrosion resistance was followed in seawater for the modified surface by using electrochemical methods. The result suggests that the water cavitation peening for 2 minutes was found to be the optimal peening parameter in terms of durability and corrosion resistance.

• Restorative Dentistry and Endodontics
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• v.9 no.1
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• pp.101-106
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• 1983

It was the purpose of this study to investigate the fracture mode of dental amalgam by observing the crack propagation, and to relate this to the microstructure of the amalgam. Caulk 20th Century Regular, Caulk Spherical, Dispersalloy, and Tytin amalgam alloys were used for this study. After each amalgam alloy and Hg measured exactly by the balance was triturated by the mechanical amalgamator (Capmaster, S.S. White), the triturated mass was inserted into the cylindrical metal mold which was 4 mm in diameter and 12 mm in height and was pressed by the Instron Universal Testing Machine at the speed of 1mm/min with 120Kg. The specimen removed from the mold was stored in the room temperature for a week. This specimen was polished with the emery papers from #100 to #200 and finally on the polishing cloth with 0.06${\mu}Al_2O_3$ powder suspended in water. The specimen was placed on the Instron testing machine in the method similar to the diametral tensile test and loaded at the crosshead speed of 0.05mm/min. The load was stopped short of fracture. The cracks on the polished surface of specimen was examined with scanning electron microscope (JSM-35) and analyzed by EPMA (Electron probe microanalyzer). The following results were obtained. 1. In low copper lathe-cut amalgam, the crack went through the voids and ${\gamma}_2$ phase, through the ${\gamma}_1$ phase around the ${\gamma}$ particles. 2. In low copper spherical amalgam, it was observed that the crack passed through the ${\gamma}_2$ and ${\gamma}_1$ phase, and through the boundary between the ${\gamma}_1$ and ${\gamma}$ phase. 3. In high copper dispersant (Dispersalloy) amalgam, the crack was found to propagate at the interface between the ${\gamma}_1$ matrix and reaction ring around the dispersant (Ag-Cu) particles, and to pass through the Ag-Sn particles. 4. In high copper single composition (Tytin) amalgam, the crack went through the ${\gamma}_1$ matrix between ${\eta}$ crystals, and through the unreacted alloy particle (core).

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.41.2-41.2
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• 2011

Recently, scaling down of ULSI (Ultra Large Scale Integration) circuit of CMOS (Complementary Metal Oxide Semiconductor) based electronic devices become much faster speed and smaller size than ever before. However, very narrow interconnect line width causes some drawbacks. For example, deposition of conformal and thin barrier is not easy moreover metallization process needs deposition of diffusion barrier and glue layer. Therefore, there is not enough space for copper filling process. In order to overcome these negative effects, simple process of copper metallization is required. In this research, Cu-V thin alloy film was formed by using RF magnetron sputter deposition system. Cu-V alloy film was deposited on the plane $SiO_2$/Si bi-layer substrate with smooth and uniform surface. Cu-V film thickness was about 50 nm. Cu-V layer was deposited at RT, 100, 150, 200, and $250^{\circ}C$. XRD, AFM, Hall measurement system, and XPS were used to analyze Cu-V thin film. For the barrier formation, Cu-V film was annealed at 200, 300, 400, 500, and $600^{\circ}C$ (1 hour). As a result, V-based thin interlayer between Cu-V film and $SiO_2$ dielectric layer was formed by itself with annealing. Thin interlayer was confirmed by TEM (Transmission Electron Microscope) analysis. Barrier thermal stability was tested with I-V (for measuring leakage current) and XRD analysis after 300, 400, 500, 600, and $700^{\circ}C$ (12 hour) annealing. With this research, over $500^{\circ}C$ annealed barrier has large leakage current. However V-based diffusion barrier annealed at $400^{\circ}C$ has good thermal stability. Thus, thermal stability of vanadium-based thin interlayer as diffusion barrier is good for copper interconnection.

• Corrosion Science and Technology
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• v.11 no.6
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• pp.263-269
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• 2012

Copper alloys are commonly applied to ship's propellers, pumps and valves which are serviced in seawater due to their good castability and corrosion resistance. In the environment of high flow velocity, however, erosion damage predominates over corrosion damage. In particular, the cavitation in seawater environment accelerates surface damage to copper alloys, resulting in degradation of products and economic losses and also threatening safety. The surface was coated with WC-27NiCr by high velocity oxygen fuel(HVOF) spraying technique to attain durability and cavitation resistance of copper alloys under high velocity/pressure flow. The cavitation test was performed for the WC-27NiCr coating deposited by HVOF in seawater at the amplitude of $30{\mu}m$ with seawater temperature. The cavitation at $15^{\circ}C$ caused exfoliation of the coating layer in 17.5 hours while that of $25^{\circ}C$ caused the exfoliation in 12.5 hours. When the temperature of seawater was elevated to $25^{\circ}C$ from $15^{\circ}C$, more damage was induced by over 160%. Although WC-27NiCr has good durability, corrosion resistance and eletrochemical stability, the cavitation damage rate of the coating layer could remarkably increase at the elevated temperatures under cavitation environments.

• Journal of Korea Foundry Society
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• v.41 no.5
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• pp.419-433
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• 2021

Al-Si-Cu alloys benefit from the addition of copper for better hardness and strength through precipitation hardening, which results in remarkably strong alloys. However, the addition of copper expands the solidification range of Al-Si-Cu alloys, and due to this, these alloys become more prone to hot tearing, which is one of the most common and serious fracture phenomena encountered during solidification. The conventional evaluation method of the hot tearing properties of an alloy is a relative and qualitative analysis approach that does not provide quantitative data about this phenomenon. In the present study, the mold itself part of a device developed in Instone et al. was partially modified to obtain more reliable quantitative data pertaining to the hot tearing properties of an Al-Si-Cu casting alloy. To assess the influence of Cu element, four levels of Cu contents were tested (0.5, 1.0, 3.0, and 5.0 wt.%) in the Al-Si-Cu system alloy and the hot tearing properties were evaluated in each case. As the Cu content was increased, the hot tearing strength decreased to 2.26, 1.53, 1.18, and 1.04 MPa, respectively. At the moment hot tearing occurred, the corresponding solid fraction and solidification rate decreased at the same temperature due to the increase in the solid-liquid coexistence range as the Cu content increased. The morphology of the fracture surfaces was changed from dendrites to dendrites covered with residual liquid, and CuAl₂ phases were observed in the vicinity of hot tearing.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.11
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• pp.1067-1073
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• 2007

This paper presents development of an special metal hydride(SMH) actuator system using a peltier module. The newly developed simple SMH actuator, consisting of the plated hydrogen-absorbing alloy as a power source, Peltier elements as a heat source and a cylinder with metal bellows as a functioning part, has been developed. The SMH actuator is characterized by its small size, low weight, noiseless operation and a compliance similar to that of human body. A new SMH actuator that uses reversible reactions between the heat energy and mechanical energy of a hydrogen absorbing alloy. It is well known that hydrogen-absorbing alloys can reversibly absorb and desorb a large amount of hydrogen, more than about 1000 times of their own volume. To improve the thermal conductivity of the hydrogen-absorbing alloy, an electro-less copper plating has been carried out. For this purpose, the effects of the electro-less copper plating and the dynamic characteristics of the SMH actuator have been studied. The hydrogen equilibrium pressure increases and hydrogen is desorbed by heating the hydrogen-absorbing alloys, whereas by cooling the alloys, the hydrogen equilibrium pressure decreases and hydrogen is absorbed. The SMH actuator has the characteristic of being light and easy to use. Therefore, it is suitable for medical and rehabilitation applications.