Infrared Brazed Joints of TiNi Shape Memory Alloy and Ti-15-3 Alloy Using Two Ag-Based Fillers.

The wettability, microstructures, and bonding strength of infrared brazing Ti-15-3 and TiNi shape memory alloy using 72Ag-28Cu (wt.%) and 68.8Ag-26.7Cu-4.5Ti (wt.%) filler metals have been investigated. Only Ticusil active braze readily wets both TiNi and Ti-15-3 substrates. Wetting of eutectic 72Ag-28Cu melt on TiNi base metal is greatly ameliorated by adding 4.5 wt.% Ti into the alloy. The brazed Ti-15-3/BAg-8/TiNi joint consists of Cu-Ti intermetallics in the Ag-rich matrix. The formation of interfacial Cu(Ti,V) and (CuNi)Ti intermetallics next to Ti-15-3 and TiNi substrates, respectively, is attributed to the wetting of both substrates. The brazed Ti-15-3/Ticusil/TiNi joint shows a vigorous reaction, which results in the formation of a large amount of TiNi intermetallics in the joint. The maximum joint strengths using BAg-8 and Ticusil filler metals are 197 MPa and 230 MPa, respectively.