Microstructure and Tensile Behavior of Laser Arc Hybrid Welded Dissimilar Al and Ti Alloys.

Fiber laser-cold metal transfer arc hybrid welding was developed to welding-braze dissimilar Al and Ti alloys in butt configuration. Microstructure, interface properties, tensile behavior, and their relationships were investigated in detail. The results show the cross-weld tensile strength of the joints is up to 213 MPa, 95.5% of same Al weld. The optimal range of heat input for accepted joints was obtained as 83-98 J·mm. Within this range, the joint is stronger than 200 MPa and fractures in weld metal, or else, it becomes weaker and fractures at the intermetallic compounds (IMCs) layer. The IMCs layer of an accepted joint is usually thin and continuous, which is about 1μm-thick and only consists of TiAl₂ due to fast solidification rate. However, the IMCs layer at the top corner of fusion zone/Ti substrate is easily thickened with increasing heat input. This thickened IMCs layer consists of a wide TiAl₃ layer close to FZ and a thin TiAl₂ layer close to Ti substrate. Furthermore, both bead shape formation and interface growth were discussed by laser-arc interaction and melt flow. Tensile behavior was summarized by interface properties.