Influence of Ag addition on the microstructure and properties of copper-alumina composites prepared by internal oxidation

Abstract

In present study, Cu-Al2O3 composites with both higher micro-hardness and electrical conductivity were fabricated by internal-oxidizing Cu-Al and Cu-Al-Ag sheets at 950 °C for 2 h. A small amount of Ag was doped as additives with atomic ratio of Ag/Al ranging from 0 to 0.25. Effects of Ag addition on microstructures, electrical conductivity and micro-hardness were investigated. Results show that the morphology and size distribution of Al2O3 in internal-oxidized Cu-Al alloys were highly sensitive to Ag addition. The size of Al2O3 precipitates decreased from ∼63 nm to ∼37 nm when increasing Ag content. Moreover, a large number of triangular Al2O3 precipitate with similar size was observed by field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscopy (HRTEM) in Ag-doped Cu-Al2O3 composites. The orientation relationship between triangular Al2O3 and Cu matrix was [112]Cu//[110]Al2O3, (111¯)Cu//(002)Al2O3 and (22¯ 0)Cu//(22¯ 0)Al2O3. Increasing the amount of Ag enhances the electrical conductivity and mechanical strength simultaneously. The optimal electrical and mechanical properties which were 85.9% IACS and 162 HV respectively, were obtained when atomic ratio of Ag/Al was ∼1:4 in internal-oxidized Cu-Al2O3-Ag alloy.