Effects of Ag on the oxidation kinetics and properties in copper-alumina composites during in-situ fabrication

Abstract

External oxidation was adopted to fabricate Cu–Al2O3 composites with Ag addition. The influences of Ag on oxidation kinetics, microstructure evolution and properties of Cu–Al2O3 composites were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and optical microscopy (OM). The external oxidation was found to be the combination of surface oxidation and internal oxidation. The parabolic rate constant (PRc), which can reflect the oxidation rate during the internal oxidation process, was analyzed by experimental measurement and theoretical calculation. The measured PRc results during external oxidation have increased by 81% to 2.14×10−8cm2/s at 1073 K and 71% to 2.63×10−7 cm2/s at 1223 K after Ag was added. It indicates that the Ag can remarkably accelerate the internal oxidation process in external oxidation. Moreover, compared with traditional internal oxidation method, the external oxidation was found to be a more efficient way to prepare Cu–Al2O3. The PRc in traditional internal oxidation are 3.58×10−9 cm2/s at 1073 K and 6.72×10−8cm2/s at 1223 K, while the PRc in external oxidation are much higher which are 1.18×10−8cm2/s at 1073 K and 1.54×10−7 at 1223 K. SEM results show that the oxide bands composed of coarsening Al2O3, have disappeared, and the size of Al2O3 precipitates dropped from ∼65.78 nm to ∼45.42 nm after Ag was added. Due to the more homogeneous microstructure caused by Ag, the electrical conductivity had a 9.48% increment to ∼85.27% International Annealed Copper Standard (IACS), and the microhardness climbed from ∼131.8 HV to ∼152.76 HV.