Microstructure and mechanical properties of TA15-Ti2AlNb bimetallic structures by laser additive manufacturing

The TA15-Ti2AlNb bimetallic samples with no defects were prepared by laser additive manufacturing. The evolution of the composition and microstructure in transition zone, and the mechanical properties were investigated. Composition in the transition region shows a step-and-platform distribution due to the rapid solidification and diffusion during the depositing process. The phase transformation from TA15 alloy side to Ti2AlNb-based alloy side is alpha (lath) +beta ->alpha (coarse acicular) +beta ->beta+alpha(2)->alpha(2)+O + B2. The TA15-Ti2AlNb bimetallic structures present tensile properties with average tensile strength of 1025 MPa and elongation of 7.3%. The fracture position of samples is located in diffusion zone, and the fracture mode is quasi-cleavage fracture. The TA15-Ti2AlNb bimetallic circular structure with bell mouth was fabricated and this work shows great potential for fabricating bimetallic structures by laser additive manufacturing technology.