Microstructure and properties at elevated temperature of a nano-Al2O3 particles dispersion-strengthened copper base composite

High softening resistance, high strength at elevated temperature and high conductivity is important performances for the high voltage breaker and vacuum interrupter contact materials. A novel nano-Al2O3–Cu composite was fabricated for them by using a modified internal oxidation method. The microstructure was investigated by means of a scanning electron microscope and a transmission electron microscopy. The softening temperature, tensile strength at elevated temperature and electrical conductivity of the composite were also determined. The grain size of the Cu–0.5 vol.% Al2O3 composite is very fine and the annealing temperature greatly affects its microstructure. The electric conductivity reaches 93% IACS and the softening temperature is about 800 °C, while the yield strength reaches 169 MPa and the ultimate tensile strength reaches 172 MPa at the testing temperature of 600 °C. The main contributions of nano-alumina particles is to strengthen the composite, not by Orowan strengthening, but due to the strong pinning effects on the grain boundaries and sub-grain boundaries with high dislocation density to prevent the nuclei formation of recrystallization.