Change laws of micro-composition and microstructure of silver-based brazing filler metal ingot

The homogeneity and microstructure of the brazing filler metal ingot are the initial conditions for the formation of brazing filler metal. These initial conditions have a significant effect on the plastic working performance and the post-processing microstructure of the brazing filler metal. The microstructures of BAg30CuZnSn brazing filler metal ingot were studied by means of OM, SEM and EDS. The results show that in the brazing filler metal ingot: Along the radial direction from the outside to the inside, Ag content gradually decreased, Cu, Zn content gradually increased. From bottom of the riser to top, Ag content gradually decreased, Cu, Zn content gradually increased. The change of the composition leads to the change of the ingot microstructure. From the external of the ingot to the central part, the grain size is gradually increased, showing the distribution from the initial random distribution to the cluster distribution. In the center of the ingot, the main phase is dendrites of rich Ag.