Effect of laser energy density on interfacial microstructure and properties of ZL114A/TC4 dissimilar joints by laser directed energy deposition

Ti/Al dissimilar structures combining lightweight design with high specific performance are attractive for aerospace and transportation applications. In this study, ZL114A was deposited on TC4 by laser directed energy deposition to fabricate metallurgically bonded joints, and the influence of laser energy density on interfacial evolution and properties was systematically investigated. The results reveal an optimal processing window of 42–50 J/mm 2 . Within this range, lack-of-fusion defects were effectively suppressed while excessive interfacial reactions were avoided, resulting in a relatively uniform hardness distribution and tensile strengths of 100 and 91 MPa, respectively. The fracture mode exhibited mixed ductile–brittle characteristics. When the energy density increased to 61 J/mm 2 , intensified Ti–Al interfacial reactions led to thick and continuous intermetallic compound layers composed of Ti 3 Al, TiAl, and TiAl 3 , accompanied by increased crack density and a sharp reduction in tensile strength to 55 MPa. Electrochemical results further indicated that excessive energy input deteriorated corrosion resistance due to IMC thickening and crack-assisted penetration of corrosive media. These findings demonstrate that controlling energy density within a moderate range is critical for balancing metallurgical bonding, interfacial stability, and overall performance of ZL114A/TC4 dissimilar joints.