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| Jílek L. |
| FORGING HISTORY |
| Keywords: |
| No 1 (2000), p. 5-19 |
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| Besterci M., Lachváč J., Velgosová O. |
| DEFORMATION OF COMPOSITE MATERIALS CU-AL2O3 |
Abstract
The industry for many years permanently demands materials with high thermal conductivity in combination with high strength characteristics at elevated temperatures. Alloys based on the copper, due to their excellent thermal and electrical conductivity are especially suitable for these applications. The development of copper alloys with their high strength properties at elevated temperatures is complicated as these alloys are hardenable by aging and exhibit a tendency to the precipitation coarsening or precipitates dissolution at higher temperatures. The addition of thermodynamically stabile dispersoids, which are resistant to the coarsening and dissolution at elevated temperatures may result in excellent mechanical properties of copper alloys used at higher temperatures. Assuming that the dispersoids are small enough < 50 nm with a small mean free path between dispersed particles, high strength can be reached by methods of powder metallurgy even at low volume fraction of dispersoids. This is very important as the lover the dispersoids content in the copper matrix the higher conductivity of the alloy.
Such materials are used for electrodes for spot welding, for powerful switchers, electro-motors, heat exchangers as well as for cooled parts of gas turbines and generators.
Deformation processes of Cu-Al2O3 composite materials prepared via powder metallurgy are assessed in the paper. Powder mixture was prepared by grinding of Cu and Al2O3 particles. After the compaction, materials were deformed by extrusion, forging and isostatic pressing. Qualitatively was evaluated their microstructure and quantitatively their mechanical properties.
By comparison of mentioned three deformation technologies we found isotropic microstructure in materials deformed by forging and isostatic pressing. Optimum properties (ultimate tensile strength and reduction of area) shoved the materials deformed by hot isostatic pressing, which possessed low residual porosity (<1 vol%).
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| Keywords: Cu-Al2O3 composites|powder metallurgy|deformation process|mechanical properties|structure| |
| No 1 (2000), p. 42-46 |
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