Laser welding of dissimilar TiAl/Ti6-Al-4V materials: Effects of rapid in-situ laser pre-heating on microstructure and mechanical properties of the welding joint

Abstract

TiAl alloy has broad application prospects in the aerospace field. In practical working environments, connecting with other materials is considered an important means of fully utilizing their excellent properties. This study employed a laser in-situ pre-scanning method to preheat the weld seam, achieving the connection between TiAl alloy and Ti-6Al-4V. On this basis, the microstructural evolution of the fusion zone (FZ), fusion line (FL), and heat-affected zone (HAZ) of the welded joint was analyzed in detail. By comparing with traditional welding processes, the effects of laser in-situ preheating on the microstructure and properties of the welded joints were studied. The results showed that the FZ area consists of α2 and martensitic α-Ti, while the FL on the TiAl side features a transition layer of β/B2 phases, providing plasticity and toughness to the welded joint. The in-situ scanning method reduced the cracks generated during welding, resulting in a more uniform distribution of the transition layer. The obtained FZ exhibited higher microhardness. The room temperature tensile strength of the welded joint reached 650 MPa. As the temperature increased, at 400 °C, the tensile strength and elongation reached 571 MPa and 3 %, respectively, significantly higher than the 450 MPa and 1.5 % achieved by conventional welding at the same temperature. When the temperature further increased to 500 °C and 600 °C, Ti-6Al-4V experienced significant softening, becoming the weak point of the welded joint.