Effect of Ce Addition on the Microstructure and Properties of Ag17CuZnSn Filler Metal

The effect of trace amounts of rare earth element Ce on the wettability, mechanical properties and microstructure of Ag17CuZnSn filler metal was investigated systematically by means of microstructure and spectroscopic characterizations. H62 brass and 304 stainless steel were brazed with Ag17CuZnSn-xCe filler metals. The results indicate that wettability and oxidation resistance of filler metal are remarkably improved with adding trace amount of Ce. The shear strength of brazed joint increases 29% compared to that of brazed joint without adding Ce. Moreover, it is observed that the trace amount of Ce in Ag17CuZnSn filler metal refines the brazed joint matrix microstructure. The elements diffusion is examined during the brazing process. More Ce can diffuse into the stainless steel than that of either Cu or Zn. Compared to the Cu solid solution, Fe prefers to diffuse into the Ag solid solution. When the Ce content is 0.3 wt.%, some bright and brittle Ce-bearing particles appear in the bottom of dimples which deteriorate the shear strength of brazed joint. The results of this study can stimulate the use of low-silver brazing filler metals for various applications.