Fabrication and properties of Cu-Al₂O₃ functionally graded nanocomposites prepared by spark plasma sintering: the effect of copper particle size and reinforcement content

In the present study, the functionally graded copper-alumina nanocomposites fabricated using spark plasma sintering process were investigated. The copper particle size and alumina reinforcement content were chosen as variable parameters. Then the microstructure, hardness, electrical resistance, and electrochemical behavior were characterized. The results showed the integrated functionally graded composites with gradient in porosity and reinforcements. The grains' mean diameters were varied from pure layer to composite ones. Also, as the primary copper particle size increases from 63 to 300 μm, the porosity level in the functionally graded sample layers increased and as a result, the hardness decreased, and electrical resistance increased. The hardness values were increased with alumina contents in functionally graded layer with the porosity level lower than about 3%. The functionally graded composite prepared with 63 μm precurcer copper powder showed the highest density, hardness, and lowest electrical resistance. Results of electrochemical measurements concluded that the polarization resistance and Warburg impedance coefficient decreased with increasing particle size and decreasing amount of reinforcement. (paper)