Abstract :
In applications like sliding electrical contacts good electrical/thermal conductivity as well as wear resistance is required besides suitable mechanical properties. Furthermore, in these types of applications it is necessary to be prevented from local welding of various parts of pieces to each other. Although the addition of ceramic particles to a conductive metal like copper can lead to decrease of above mentioned physical properties, the producing of copper matrix composites can induce high tensile strength, better wear resistance, and resistance to electrical current with high amperage improvement. Hence, at the present study, the copper based composites containing 2, 3 and 5 vol. % ultra-fine grained yttria stabilized zirconia (YSZ) particles were produced by powder metallurgy and spark plasma sintering (SPS) method. The distribution of reinforcing particles at the microstructure was carefully studied using electron microscopy. Additionally, the density, hardness and thermal conductivity values of the specimens were measured. Referring to the results, microstructural analysis showed satisfactorily distribution of reinforcement particles in copper matrix and the clustering of particles is not so noticeable. The relative density up to 95% for all specimens was obtained due to the sintering procedure. As a result of the presence of hard stabilized zirconia particles, an increase of 60 percent in the Brinell hardness of the Cu-5 vol.% YSZ composite sample was observed in comparison with unreinforced copper. Moreover, the determined thermal conductivity values decreased from 397 to 241 W/m K with increasing of reinforcement content from 0 to 5 vol. %. The variation in the thermal conductivities can be related to the microstructural characteristics such as reinforcement and porosity volume percent as well as other microstructural defects.
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