Correlation of the microstructure and mechanical properties of oxide-dispersion-strengthened coppers fabricated by internal oxidation

Abstract

This study was aimed at the correlation of the microstructure and mechanical properties of oxide-dispersion-strengthened (ODS) coppers fabricated by internal oxidation. Atomized copper powders mixed with Cu2O oxidant powders were internally oxidized and then hot extruded to fabricate ODS coppers without defects. In order to sufficiently oxidize copper powders, oxidant powders should be added in amounts 30 pct in excess of the stoichiometrically calculated amount. In the extruded ODS coppers, very fine Al2O3 dispersoids of 10 nm in diameter were homogeneously distributed inside copper grains of 1 µm in size. The volume fraction of Al2O3 dispersoids increased as the Al content in atomized copper powders increased. With increasing volume fractions of Al2O3 dispersoids, the yield and tensile strengths increased, while the elongation and electrical conductivity decreased, and all the properties of the ODS coppers were sufficiently above the required properties of electrode materials for spot welding. To understand the mechanism responsible for the improvement of the yield strength of the ODS coppers, yield strength was interpreted using the Orowan’s strengthening model, which was fairly consistent with the experimental results.