Study on the microstructure and mechanical properties of diffusion brazing joint of C17200 Copper Beryllium alloy

In order to study the microstructure and mechanical properties of Copper Beryllium alloy, spreadability test was carried out at two temperatures under Argon atmosphere for different filler metals of Ag content. The results show that BAg2a (Ag–26Cu–21Zn–19Cd) and BAg1a (Ag–18.5Cu–17Zn–14.5Cd) are the best choice for brazing of Copper Beryllium. Zn affects the wetting of interlayer because it spreads preferentially. The bonding process was carried out at a temperature ranging of 650–800 °C for various times under Argon atmosphere using of BAg2a (Ag–26Cu–21Zn–19Cd) film with 100 μm thickness as interlayer. Interfacial microstructures were examined by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The eutectic and intermetallic compounds such as CuZn, AgZn3 and AgCd3 were formed at the interfaces between the interlayer and substrate. Microhardness and tensile tests were used for evaluating the mechanical properties. Average of hardness at the center of brazed seam decreased with increasing time and temperature that associated with diffusion of main elements to substrate and intermetallic formation at the interface. Maximum tensile strength of 170 MPa was obtained at 750 °C for 20 min for filler metal BAg2a without heat treatment and 227 MPa with heat treatment.