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류성수
- Journal of Powder Materials
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- v.7 no.2
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- pp.93-101
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- 2000
In order to clarify the enhanced sintering behavior of nanostructured(NS) W-Cu powder prepared by mechaincal alloying, the sintering behavior during heating stage was analysed by a dilatometry with various heating rates. The sintering of NS W-Cu powders was characterized by the densification of two stages, having two peaks in shrinkage rate curves. The temperature at which the first peak appear was much lower than Cu melting point, and dependent on heating rate. On the basis of the shrinkage rate curves and the microstructural observation, the coupling effect of nanocrystalline W-grain growth and the liquid-like behavior of Cu phase was suggested as a possible mechanism for the enhanced sintering of NS W-Cu powder in the state.
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김태형
- Journal of Powder Materials
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- v.1 no.2
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- pp.174-180
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- 1994
Electrical contact property of the W-20wt%Cu contact materials manufactured by liquid phase sintering of nanocomposite W-Cu powders was investigated and discussed in terms of microstructural development during performance test. Nanocomposite powders were prepared by hydrogen reduction of ball milled W-Cu oxide mixture. They underwent complete densification and microstructural homogenization during liquid phase sintering. As a consequence, the W-Cu contacts produced from nanocomposite powders showed superior contact property of lower arc erosion and stable contact resistance. This might be mostly due to the fact that the arc erosion by evaporation of Cu liquid droplets and surface cracking remarkably became weakened. It is concluded that the improvement of anti-arc erosion of the composite specimen is basically attributed to microstructural homogeneity.
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Kim, Bo-Su;An, In-Seop
- Korean Journal of Materials Research
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- v.5 no.6
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- pp.627-632
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- 1995
W-Cu composites utilize the high electrical conductivity of copper and arc erosion resistance of tungsten to provide properties better suited to electrical contact applications than either tungsten or copper alone. W-Cu composite materials were milled in an attritor with an impeller speed of 300rpm for various milling times. The milled powders were compacted at 300MPa into cylinders, 16m in diameter, and approximately 4m high. Sintering was performed in dry H$_2$at temperature ranging from 1200$^{\circ}C$ to 1400$^{\circ}C$. Samples were sectioned and were polished for scanning electron microscopy (SEM) of microstructures. Homogeneous W-Cu composites were formed after 10 hours mechanical alloying and could be attained 99% density at 1330$^{\circ}C$. As mechanical alloying time increased, Fe-concentration was increased linearly. Intermetallic compound formation interupted the growth of W particles Increased hardness.
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Park, Ji-Hwan;Kim, Su-Bang;Park, Yun-U
- Korean Journal of Materials Research
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- v.10 no.3
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- pp.227-232
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- 2000
Cu-W composites containing 20wt.% W were fabricated by hot pressing. Hot pressing was carried out at temperatures ranging from 800 to $1000^{\circ}C$ under pressures of 15MPa for 30MPa for 30min and 60min. This process gave composites of higher density, higher hardness and higher wear resistance than the conventional sintering processes. However, the microstructure of Cu-W composites under pressure of 15MPa revealed there was an inhomogeneous distribution of W, segregation of W on some area. These undesirable results are attributed to the immiscibility of W in Cu and the pressure effect on sintering.
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