Brazing of Be with CuCrZr-bronze using copper-based filler metal STEMET

Optimization of the composition of the Cu-Ni-Sn-P system filler metals and comparative tests of filler metals of various compositions have been carried out in this paper to reduce the brazing temperature of beryllium with CuCrZr. Alloys of the following compositions Cu-6.4Ni-9.2Sn-6.3P (STEMET 1105) and Cu-9.1Ni-3.6Sn-8.0P (STEMET 1101) were made in the form of rapidly quenched ribbons with a thickness of 50 µm and a width of 50 mm. They were used to perform furnace brazing by Joule heating (with a rate of 15 K/min) of beryllium with CuCrZr (Be/CuCrZr) at temperatures of 650, 700 and 750 °C for 15 min. Metallographic investigations of the zone of brazing and mechanical shear tests of joints before and after the heat treatment at 350 °C for 30 h have been conducted. It was found that the joints of Be/CuCrZr brazed at 650 °C using STEMET 1105 (τs = 230 MPa) and at 750 °C using STEMET 1101 (τs = 260 MPa) had the best shear strength properties. However, there is a significant decrease of the microhardness of CuCrZr from 1570 to 1140 MPa at 750 °C, which indicates a significant loss of its strength. The results obtained suggest that the brazing of beryllium with CuCrZr using STEMET 1105 at 650-700 °C will not adversely affect the CuCrZr.