Infrared Brazed Joints of Ti(50)Ni(50) 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 Ti(50)Ni(50) 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 Ti(50)Ni(50) and Ti-15-3 substrates. Wetting of eutectic 72Ag-28Cu melt on Ti(50)Ni(50) base metal is greatly ameliorated by adding 4.5 wt.% Ti into the alloy. The brazed Ti-15-3/BAg-8/Ti(50)Ni(50) joint consists of Cu-Ti intermetallics in the Ag-rich matrix. The formation of interfacial Cu(Ti,V) and (Cu(x)Ni(1−x))(2)Ti intermetallics next to Ti-15-3 and Ti(50)Ni(50) substrates, respectively, is attributed to the wetting of both substrates. The brazed Ti-15-3/Ticusil(®)/Ti(50)Ni(50) joint shows a vigorous reaction, which results in the formation of a large amount of Ti(2)Ni intermetallics in the joint. The maximum joint strengths using BAg-8 and Ticusil(®) filler metals are 197 MPa and 230 MPa, respectively.