Microstructure and mechanical properties of brazing joint of silver-based composite filler metal

Abstract

In this article, environmental friendly BAg25Cu40Zn34Sn (BAg-25) and BAg30Cu37Zn32Sn (BAg-30) flux-core solder metal capable of facilitating automatic production of brazing manufacturing processes were prepared. The butt and lap induction brazing tests were carried out on the substrate with BAg-25 and BAg-30. Wettability, microstructure and mechanical properties of the solders on the base metal were studied by field emission scanning electron microscope (SEM-EDS), electron backscattering diffraction (EBSD), tensile testing machine and microhardness tester. Results indicated that the wetting property of BAg-30 with 30% silver content was better than that of BAg-25 with 25% silver content. At the same time, besides copper and silver-based solid solutions, the brazed joint of BAg-30 solder also contain Cu + Ag eutectic phase. In the brazed joint of BAg-25 solder, the grain size is smaller, which makes the tensile strength and the shear strength of the joints better. Therefore, the BAg-25 flux-core solder metal will further reduce the industrial cost and meet the requirements of mechanical properties.

Keywords

• composite filler metal
• induction brazing
• wettability
• microstructure
• grain refinement