Design of high strength Cu alloy interlayer for mechanical bonding Ti to steel and characterization of their tri-layered clad

Cu-8 wt.% Ag alloy is proposed as a good interlayer alloy with good deformability, high strength, least reactivity and low melting temperature for low temperature joining of Ti and carbon steel. Titanium and carbon steel plates with a Cu-8Ag interlayer plate were joined by high pressure torsioning (HPT) at room temperature and the effect of post-HPT annealing on their mechanical performance was examined. The most pronounced increase of the Vickers microhardness (from 88 to 248 Hv) was observed in Cu-8Ag, suggesting Cu-Ag is the ideal bonding interlayer with a lower melting temperature, an initial excellent deformability and high strength after joining. With the increase of heat-treatment temperature, the tensile strength increased initially up to 350 degrees C and then decreased with increase of annealing temperature above 350 degrees C. The maximum strength after annealing at 250 degrees C is due to the combined effect of the precipitation strengthening of Cu-8Ag interlayer and static strain aging of both S20C and Ti. The stress-strain curves exhibited the step-wise fracture, with the first step resulting from the fracture of S20C plate and the next from co-fracture of Ti plate and Cu-Ag interlayer. The co-fracture of Cu-8Ag and Ti suggests that the bonding strength between two layers is fairly high even in the presence of intermetallic layer. (c) 2013 Elsevier Ltd. All rights reserved.