Low temperature brazing characteristics and mechanical properties of Ag-Cu-Sn alloys

Abstract

This study focuses on Ag-Cu-Sn ternary alloys used as brazing filler metals. These alloys are known to have a high wettability and a low melting temperature. However, the alloys become brittle by the addition of large amounts of Sn. In this study, we investigated the brazing characteristics and the mechanical properties of Ag-Cu-Sn ternary alloys that contain Sn in the range of 15 to 30 wt.% Sn, which have not been reported until now. 47.5 wt.% Ag-25.5 wt.% Cu-27.0 wt.% Sn alloy was compatible ratio with low melting temperature and high wettability. However the alloy was very brittle because of the existence of Cu₃Sn. This material is known as hard and brittle intermetallic compounds. We added Ni to the alloy to improve the brittleness. 1 wt.% Ni addition improved its rupture strain significantly. It is suggested that the good mechanical properties are derived from production of (Cu, Ni)₃Sn intermetallic compounds and grain coarsening.