Generation and characterization of T40/A5754 interfaces with lasers

Abstract

Laser-induced reactive wetting and brazing of T40 titanium with A5754 aluminum alloy with 1.5 mm thickness was carried out in lap-joint configuration, with or without the use of Al5Si filler wire. A 2.4 mm diameter laser spot was positioned on the aluminum side to provoke spreading and wetting of the lower titanium sheet, with relatively low scanning speeds (0.1 to 0.6 m/min). Process conditions did not play a very significant role on mechanical strengths, which were shown to reach 250-300 N/mm on a large range of laser power and scanning speeds. In all cases considered, the fracture during tensile testing occurred next to the TiAl3 interface, but in the aluminum fusion zone. In a second step, we have investigated the interfacial resistance with the LASAT bond strength tester, based upon the generation and propagation of laser-induced shock waves. This allowed us estimating a uniaxial bond strength of 0.68 GPa for the T40/A5754 interface under dynamic loading conditions.