Manufacturing Process And Property Of Al₂O₃Strengthened Copper-based Composite Material

Al2O3-particle-reinforced copper-based composites that combine highstrength, high conductivity and high wear resistance, promise great applicationin the wide fields of electronic, electrical and public transport. In practicalapplication of Cu-Al2O3composites, Al2O3nanoparticles, however, tends toaggregate when conventional casting or powder metallurgy method is employed,resulting in their inhomogeneous dispersion in the matrix. At the same time,their poor wettability with respect to copper substrates leads to poor adhesion ofalumina particles to copper matrix. These two factors combined together willgreatly compromise the performance of the resultant composites. As a result, itis of great significance to well disperse alumina nanoparticles in copper matrixand meanwhile improve the interfacial wettability for better mechanicaladhesion.In this paper, we demonstrated the preparation of Cu-Al2O3composites byin-situ process where Al2O3nanoparticles were formed in the copper matrixthrough the decomposition of aluminum nitrate. This approach as-developed,not only significantly improves the interfacial wettability at the Cu-Al2O3interface, but also emphasizes the homogeneous dispersion of Al2O3nanoparticles in copper matrix.The decomposition process of aluminum nitrate was investigated by usingdifferential thermal-differential gravimetric analysis. The dehydration reactionof aluminum nitrate was confirmed to start at about80℃whereas itsdecomposition at about560℃. The resultant Al2O3nanoparticles show smoothedge, uniform size and good dispersibility.Cu-Al2O3composite powders are prepared by using the external-reinforcementmethod and in-situ synthesis method, followed by a resintering process to formCu-Al2O3composites. The optimized process parameters are confirmed to be apreloading pressure of300MPa, a sintering temperature of900℃, a sinteringtime of1hour, a complex pressure of500MPa, an annealing temperature of800℃, and a holding time of1hour.The density and relative density of the samples were tested by Archimedesdrainage method. It is found that the composite materials as-prepared by in-situ method have higher relative density than that by the external-reinforcementmethod. Analysis of the fracture morphology suggests that the in situ approach,compared to the external-reinforcement method, benefits the homogeneousdistribution of Al2O3.Cu-Al2O3composites were fabricated by varying the volume fraction ofAl2O3with the above two methods. The properties the composites, includingelectrical conductivity, thermal conductivity, hardness, friction and wearproperties, were characterized. The results suggest that both the electricalconductivity and thermal conductivity will decrease whereas the hardness,friction and wear properties of materials will increase gradually in the presenceof an increase in Al2O3content from0.5%to3.0%. For the same amount ofAl2O3, the composites as prepared by the in-situ synthesis method show betterperformance. In the presence of an alumina volume fraction of2.0%, thecomposite materials show excellent integrated performance, including highstrength and abrasion resistance while maintaining good electrical and thermalconductivity.