Study On Copper Matrix Composite Reinforced With Alumina Particles

The Cu matrix composite reinforced by Al₂O₃ particles (Al₂O₃/Cu) is one kind of important structural and functional material with high strength and high conductivity, and has great potential applications. In this research, cold-pressing and twice sintering method was used to synthesize Cu matrix composite reinforced by Al₂O₃ particles and then the mechanical property tests of as-prepared samples were conducted. The influences of material preparing technique parameters on the quality and properties of composites in the experiments were also explored. The SEM and EDX have been used to study microstructure of Al₂O₃/Cu composite for investigating the relationship between microstructure and mechanical behaviors. In this paper, the Cu matrix composites reinforced by Al₂O₃ particulates have been prepared by the process of briquet sintering plus repress and resintering.The effects of parameters of materials preparing techniques on the properties of the material have been studied. The Al₂O₃ particulates have the sizes of 1.5μm,7μm and 10μm respectively .The volume percentages of the particulates are 5%,10%and 15% respectively.The results indicate that high quality composite can be obtained under suitable synthesizing conditions as following: powder mixing time of Al₂O₃/Cu 4～5h; initial press pressure 8MPa～9MPa, secondary press pressure 4MPa～5MPa; baking 440℃×90min, initial sintering (960℃～980℃) ×(100min～120min), secondary sintering 900℃×100min. The first sintering is the key factor of affecting the density and property of Al₂O₃/Cu composites, and the second pressing and sintering are able to increase the density and improve the property of the composites further. Well sintering atmosphere and suitably increasing of sintering temperature and sintering time can benefit the combination between Al₂O₃ particles and Cu matrix, enhance the sintering density and the properties of the composites. At the same time, the results of microstructures observation show that the Al₂O₃ particulate distribution is uniform, and the interfacial bonding between the particulates and Cu matrix is well. The Al₂O₃ particles with diameters of 7μm and 10μm are well dispersed in Cu matrix compared to particles with diameter of 1.5μm. To get well dispersion of particles in the matrix, suitable amount of particles is necessary. The small amount of particles dispersed in matrix (below 5vol%) can result in bad dispersion and the big amount (over 15vol%) will lead to the aggregation and the adhesion of reinforced particles. The mechanical testing results of Al2O3/Cu composites indicate the tensile strength and the elongation of Cu matrix materials can be decreased by addition of Al2O3 particles. The tensile properties of composites decrease with the increase of the size and amount of Al2O3 particles in matrix. The introduction of Al2O3 particles can largely enhance the abrasion resistance of Cu matrix materials. Larger amount of Al2O3 particles such as ten percent and fifteen percent can bring better abrasion resistance of composites compared to lower amount of five percent. To obtain high abrasion resistance of composites, suitable diameter of particles ( about 7μm) is better than other sizes of particles (such as 1.5μm and 10μm). Hardness testing results of composites show hardness of Cu matrix materials can be enhanced with suitable size and amount of Al2O3 particles in matrix. From microstructure analysis using SEM and EDX, it is found the interface of Al2O3-Cu is well combined ,and the dispersion of reinforced particles in matrix is uniform. In the interface of Al2O3-Cu, there exists a diffusion layer of three elements of Cu, Al and O. In the diffusion layer, some new matter exist, consisting of three elements Cu, Al, O. Moreover , the phase transition of Al2O3 may also occure during the processing of composites. In summary, research indicates cold-pressing and twice sintering method applied to synthesize Al2O3-Cu composites is simple and operable. The composites prepared by this method have excellent abrasion resistance, preferably tensile strength and elongation,and certain enhancement of hardness.