| Dispersion strengthened copper matrix composite attracts most of the attention for its excellent high strength, high electrical conductivity property, good property on electrical sliding wear conditions and high resistance to softening at elevated temperatures. The main character of dispersion strengthen copper matrix composite is tiny strengthened phase particles of dispersion distribution in copper matrix. The main characteristic parameters of strengthening phase particles include their own features characterization parameter of particles and the distribution characteristic parameters (the number, size and spacing, etc.) of particles in copper matrix. The superior performance of copper matrix composite is closely related to the characteristic parameters of dispersion strengthening phase particles, so the design problem of strengthening phase particles characteristic parameters is the primary issue of dispersion strengthen copper matrix composites.The Al2O3, MgO, SiO2and SiC four different dispersion nanometer particles are selected as the research object in this paper. The different volume fraction nanoparticles reinforced copper matrix composites are prepared by powder metallurgy technology. The hardness, density, electrical conductivity and the thermal expansion coefficient of copper matrix composites are determined. The influences of types, size and volume fraction of strengthen phase on the properties of density, hardness, electrical conductivity, thermal expansion coefficient and wear behavior of copper-based composites are studied. The microstructure of the copper matrix composite was also examined with scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDS) and transmission electron microscopy (TEM). The research is to explore the theory basis for the production of the dispersion strengthened copper matrix composite and material design of application on current-carrying friction field.The main conclusions are as follows: 1. After hot extrusion, density and electrical conductivity of copper matrix composites both decreased with the increase of the volume fraction; whereas the hardness is increased, then decreased. Under this experiment condition, when volume fraction of strengthen phase particle is achieved2.0%, comprehensive properties of copper matrix composites are obviously increased. The mierostructures revealed that the second phase particles precipitated dispersedly in copper matrix after hot extrusion. With the increase of the strengthen phase particle volume fraction, nanoparticles appear together in grain boundary of copper matrix.2. Along with the increase of volume fraction of nano-particles, the thermal expansion coefficient of copper matrix composites are reduced. Among the four copper-matrix composites of Al2O3/Cu, SiO2/Cu, SiC/Cu and MgO/Cu, the thermal expansion coefficient of MgO/Cu composite was lower than other three composites of Al2O3/Cu, SiO2/Cu, SiC/Cu at the temperature from100℃to300℃, whereas the SiO2/Cu composite had the lowest thermal expansion coefficient values when the temperature rose up to300℃.3. Within the experiment range, along with the increase of Al2O3particle size, wear rate of Al2O3/Cu composites presented to reduce after increasing. When the particle size is200nm, wear rate is the lowest and friction and wear performance is improved.4. Within the experiment range, the wear rate of copper matrix composites and the difference of the thermal expansion coefficient of matrix and its particle and the melting point of particles have the coherent variation trend, the difference of thermal expansion coefficient of enhance phase particles and matrix is smaller and the particle melting point is higher, then the composite material wear rate of copper matrix composite is low. In the flow conditions, the wear surface of the copper matrix composites is dominated by plastic deformation, and adhesive wear and electric ablation wear. |
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