Force enhanced wire laser additive manufacturing of aluminum and titanium alloys

Brittle intermetallic compound formation is typically difficult to avoid during fusion joining of dissimilar metals. In this paper, a new approach called force enhanced wire laser additive manufacturing is proposed to join aluminum and titanium alloys. Ti6Al4V titanium alloy single track was additively fabricated on AA7075 plate successfully, through two liquid pools of the wire and the substrate, separated by a buckled unmelted part of the wire, leading to a mechanically interlocked interface. The effects of manufacturing parameters including laser power, wire feeding speed, scanning speed and initial contact force between wire and substrate on the surface morphology, internal interface microstructure and formation of intermetallic compounds were investigated through high-speed camera, spectrometer, laser topography, optical imaging, SEM imaging, XRD characterizations along with numerical simulations at different scales. And the maximum tensile strength reached 380 MPa in the tensile test. The experimental and numerical results indicate that the thermal modulation approach can effectively control the formation of brittle compounds between titanium and aluminum alloys and that the initial contact force ensures a good bond between the two metals.