The dissimilar joining of alumina ceramic to copper is widely used in strategic and important industries such as aerospace, nuclear and industrial equipment. In this study, the joining of alumina to copper with active filler metals Ag-Cu-Ti-Sn, Ag-Cu-Ti-Sn-%3.5Zr and Ag-Cu-Ti-Sn-%5.1Zr using the brazing process. Induction brazing was done at temperatures of 840, 860 and 880 degrees Celsius for 15 minutes and under a vacuum of 10-6 millibars. The thickness of filler metals Ag-Cu-Ti-Sn, Ag-Cu-Ti-Sn-%3.5Zr and Ag-Cu-Ti-Sn-%5.1Zr were measured as 155±10, 250±10 and 130±10 micrometer respectively after the cold rolling process. This study was designed to investigate the synergistic effect and the addition of zirconium element to filler metals in the brazing process. The microstructure of joints was eva‎luated using optical and scanning electron microscopes equipped with energy dispersive analysis and the mechanical properties of joints were eva‎luated using shear strength and microhardness tests. In addition, the fracture surfaces of the samples obtained from the shear strength test were fractured by a scanning electron microscope. The results of the microstructural eva‎luation of the joints showed that the joint area is divided into several separate areas under the name of the reaction layer area, the brazing area and the area Diffusion affected zone. Al2O3/Cu joining brazed using Ag-Cu-Ti-Sn filler was observed in the brazing area of Ag-Cu eutectic compound with copper base and in the reactive layer area of two phases TiO and Cu3Ti3O. The brazed Al2O3/Cu joining using a filler containing %3.5 by weight of zirconium was observed in the brazing area of the Ag-Cu eutectic structure with copper base and in the area of the reactive layer of two oxide phases of TiO and ZrO2. Also, intermetallic compounds Cu3Sn and Cu6Sn5 were found in the brazing area. The brazed Al2O3/Cu joining using a filler containing %5.1 by weight of zirconium was observed in the brazing area of two phases rich in copper and silver and in the area of the reactive layer of two oxide phases of TiO and ZrO2. Cu4AgZr intermetallic compounds were also found in the brazing area. The results of the shear strength test showed that the joining with the filler metal containing %3.5 by weight of zirconium has the highest shear strength with 14 MPa due to the higher thickness of the filler metal and the lower thickness of the reaction layer. The results of the microhardness test showed that the highest hardness value is in the sample whose filler metal contains %5.1 by weight of zirconium, and the highest hardness in each sample was obtained in the reaction layer area. Scanning electron microscope images of fracture surfaces show the occurrence of quasi-brittle fracture in all samples.

مرتضي شمعانيان اصفهاني , عباس بهرامي

قاسم عظيمي روئين

حميدرضا سليمي جزي , مهدي رفيعائي