Infrared Brazed Joints of Ti50Ni50 Shape Memory Alloy and Ti-15-3 Alloy Using Two Ag-Based Fillers

Abstract

The wettability, microstructures, and bonding strength of infrared brazing Ti-15-3 and Ti50Ni50 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 Ti50Ni50 and Ti-15-3 substrates. Wetting of eutectic 72Ag-28Cu melt on Ti50Ni50 base metal is greatly ameliorated by adding 4.5 wt.% Ti into the alloy. The brazed Ti-15-3/BAg-8/Ti50Ni50 joint consists of Cu-Ti intermetallics in the Ag-rich matrix. The formation of interfacial Cu(Ti,V) and (CuxNi1−x)2Ti intermetallics next to Ti-15-3 and Ti50Ni50 substrates, respectively, is attributed to the wetting of both substrates. The brazed Ti-15-3/Ticusil®/Ti50Ni50 joint shows a vigorous reaction, which results in the formation of a large amount of Ti2Ni intermetallics in the joint. The maximum joint strengths using BAg-8 and Ticusil® filler metals are 197 MPa and 230 MPa, respectively.