Laser additive manufacturing of bimetallic structure from TC4 to IN718 via Ta/Cu multi-interlayer

Titanium alloys and nickel-based alloys have their own unique properties, and the bimetallic structure composed of the two alloys can be widely used in the aerospace field. However, the bimetallic structure which is fabricated by directly joining titanium alloys and nickel-based alloys via traditional methods is more sensitive to cracks due to the formation of intermetallic compounds. In this work based on laser additive manufacturing (LAM) technology, the TC4/IN718 bimetallic structure without metallurgical defects (such as cracks) was successfully fabricated via a Ta/Cu multi-interlayer. The test results indicated that the Ta/Cu multi-interlayer could effectively avoid the generation of Ti-Ni and Ti-Cu intermetallic compounds between TC4 and IN718. A good metallurgical combination was formed in each interface from TC4 to IN718 without metallurgical defects. The phase evolution from the TC4 region to the IN718 region was as follows: alpha-Ti -> alpha-Ti + beta-Ta -> beta-Ta -> beta-Ta + gamma-Cu -> gamma-Cu -> gamma-Cu +gamma-Ni + laves -> gamma-Ni + laves. The ultimate tensile strength of the bimetallic structure at room temperature was 369.32 MPa.