Cr effects on the electrical contact properties of the Al2O3-Cu/15W composites

Abstract

In order to investigate the effects of chromium on the electrical contact properties of the Al2O3-Cu/15W composites, vacuum hot-pressing sintering and internal oxidation methods were employed to fabricate the Al2O3-Cu/15W and Al2O3-Cu/15W5Cr composites. The microstructure was analyzed by scanning and transmission electron microscopy. The electrical contacts testing was performed using the JF04C testing machine at 30 V DC with 10-30 A current. The effects of Cr on the comprehensive properties, arc erosion morphology and welding force of the electrical contacts were investigated. The mass transfer mechanism was discussed. It was demonstrated that the Al2O3 nanoparticles pinned dislocations. The diffraction spots of the Cu matrix and the γ-Al2O3 disclose an orientation relationship of <103>Cu//<103>γ-Al2O3,{020}Cu//{040}γ-Al2O3. A typical arc erosion morphology, such as needle-like and coral structures was formed, which provides significantly enhanced arc erosion resistance of the contact material. Compared with the Al2O3-Cu/15W composite, the Al2O3-Cu/15W5Cr composite has a lower welding force. The two composites present two distinct mass transfer trends before and after 25 A. The final mass transfer direction of the composites is from the cathode to the anode. The Al2O3-Cu/15W5Cr contacts have less mass change under all testing conditions.