| High strength high conductivity copper alloy-based composites are extensively applied in the electromechanical, electronic, atomic energy, etc high-tech fields. It attracts more and more attention from all the countries in the world. Material researchers from all over the world make great efforts on the preparation technology and basic theory of the copper alloy-based composites. Particles reinforced copper alloy-based composites can keep the high electrical and high thermal conductivity of pure copper, and at the same time due to the addition of discontinuous reinforcements the composites can possess an ideal comprehensive properties. In the paper further research was made on nano-particles reinforced copper-based composites. It is expected to develop a new kind of functional materials with high strength, high electrical and high thermal conductivity.Commercial spot welding electrode materials are Cu-Zr, Cu-Cr, Cu-Cr-Zr alloys made by casting. Their electrical conductivity is about 70%IACS, relatively high, but their softening temperature is only 500℃. Their strength is relatively low at high temperature. So in the dissertation Nano- AlN reinforced CuCrZr composites have been fabricated successfully with almost full density, relative density 96.9%, by conventional powder metallurgy, that is, a process of pressing, sintering, re-pressing, re-sintering. It has a good combination of properties of high strength, high thermal and high electrical conductivity. The alloying powders wwere made by way of mechanical milling. The following research aspects have been done.The evolution law of microstructure, particle morphology and mechanical properties has been investigated of the three kinds of powders Cu-AlN, Cu-Zr-AlN, Cu-Cr-Zr-AlN during mechanical milling process. The appreciate preparation conditions for fine, uniform and alloying powders are obtained for milling process, which is beneficial for lowering sintering temperature, shortening sintering time. The function of n-AlN particles is analyzed during milling process.Different composites with different density were prepared using different pressures and different sintering temperatures. In order to improve their density, the technology of re-pressure and re-sintering was used. Composites with almost full density were prepared using the appropriate condition. The function of n-AlN particles is analyzed during densification. The density of the composite Cu-Cr-Zr-AlN is 96.9% by the process of 500MPa pressing, 900℃sintering, then 600MPa re-pressing,900℃re-sintering.Microstructure and morphology of the n-AlN particles reinforced copper composites, with almost full density, were characterized using OM, SEM, TEM, HRTEM, XRD, EDS, HB, HV etc. That the composite structure inherits that of the raw materials was discovered. The composites have uniformly, fine and relatively compacted microstructure. The tensile strength ,the bending strength, the softening temperature of the composites are 600MPa, 401MPa, > 700℃respectively made using the process, 500MPa pressing, 900℃sintering , then 600MPa re-pressing, 900℃re-sintering. The characteristics of the pores' influence on mechanical properties were analyzed. The influence of solid solution and aging on mechanical properties and the function of Nano-particles were analyzed. The change of microstructure and morphology during heat treatment was characterized and the reason for the change was found.The thermal conductivity and the electrical conductivity of the composites were measured. The thermal conductivity and the electrical conductivity of the composites were 190Wm-1K-1, 64% IACS respectively made using the process, 500MPa pressing, 900℃sintering, then 600MPa re-pressing, 900℃re-sintering. The mechanism of thermal conductivity and electrical conductivity was analyzed. The n-particles' influence was emphasized on the thermal and electrical conductivity. The relation between the thermal and electrical conductivity of the composite was compared with Lorents constant. The ratio of the thermal and electrical conductivity of the composite didn't equal to Lorents constant. The composites were treated by solid solution and aging. The behaviour of n-particle, Zr and Cr was analyzed. The optional technology for heat treatment was obtained.The optional properties of the composites, the tensile strength ,the bending strength, the softening temperature of the composites are 600MPa, 401MPa, > 700℃respectively made using the process, 500MPa pressing, 900℃sintering , then 600MPa re-pressing, 900℃re-sintering. Using the above preparation conditions the composite was made into a kind of spot welding electrode. The performance of the electrode was rationalized on the spot. The axial shortage of the electrode and the number of welding dots were recorded. Comparing with the commercial spot welding electrode's life, that of the self-made composite electrode was raised by 20%. The microstructure of the dis-functional composite electrode was characterized by OM, SEM, TEM. The dis-functional mechanism of the composite electrode was analyzed and the reason for long life was summoned.
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