Investigation On Cu-Al₂O₃ Composites Synthesized By Reaction-Casting

A series of Cu-Al2O3 composites were synthesized by Reaction -Casting which meant that the molten copper in which the mixed-powder of Cu2O, Al and Cu reacted was stirred equably and then was cooled down in the mould. Moreover the effects of the temperature of molten copper and the content of Al powder in the mixed-powder on microstructure and properties (hardness, conductivity) of the material were studied. The results indicated that:1 . Analyzing the reaction of CuiO and Al in thermodynamics and kinetics showed that Al2O3 particles could be gotten by the reaction between Cu2O and Al in molten copper.2. With the increase of the temperature of molten copper, the reaction between Cu2O and Al got more complete and the quantity of Al2O3 particles in molten copper became greater when the content of Al in the mixed-powder was about 11.5%. There was a critical temperature Tm between 1200 ~1215 . Above the Tm the relationship between the temperature and the extent of reaction of Cu2O and Al, which would react completely by keeping the time of holding temperature longer or rising temperature higher, is of liner relation.3. When the molten copper temperature at 1200 and the content of Alin mixed-powder more than 16.5%, the microstructure and properties of the Cu-Al2O3 composites were more satisfying. Being affected more by microscopic motion state of Cu2O and Al in the molten copper, the reaction between Cu2O and Al reacted non-uniformly while the content of Al in mixed-powder is less than 16.5%.4. The conductivity of the composites was not only depended on the content of Al2O3 particles in the material but also depended on the spaces of dendrites.5. The solidification of molten copper would vary from directional solidification to non-directional solidification with the temperature changed from low to high. For the exist of Al2O3 particles in the front of the interface between solid phase and liquid phase changing the thermal diffusion conditions, the evolution of ultimate microstructure of the composites was like as the solidification of single-phase alloy.6. The preparation of Cu-Al2O3 Composites by Reaction -Casting not only had the theoretical basis but also could be operated safely.