Study on microstructure and mechanical properties of vacuum brazing joints of copper1

The amorphous ribbons filler metal and as-cast filler metal of Cu-Ni-Sn-P which have the same compositions were prepared by means of rapid solidification and ordinary casting method respectively. Two kinds of filler metals were brazed with copper by vacuum brazing under 660, 670, 680, 690 ℃ and the holding time was 5, 10, 15 min. The interface microstructure and fracture appearance of brazing joints were studied by means of DTA, XRD, EDS and metalloscope. Bonding strength of joints were evaluated by tension test. The results showed that the tensile strength was the highest when heated at 680 ℃ for 15 min. Tensile strength of amorphous filler metal were better than that of as-cast filler metal. The interface reaction layer was composed of diffusion zone and residual brazing filler region. With the increasing of brazing temperature and holding time, the depth of diffusion and metallurgy combination were between base metal and filler metals increase. Intergranular priority diffusion was obvious at the direction of base depth.