Microstructure Characteristics and Mechanical Properties of γ-TiAl/Steel Joints with Different Laser Pulse Currents

Dissimilar welding of γ-TiAl alloy and steel is applied by laser with different laser pulse current (80A, 85A and 90A). The dissimilar laser weldability of γ-TiAl alloy and steel is investigated on laser welding without and with V/Cu filler metals. The results reveal that the brittle FeAl, Fe2Ti, Fe2Al5, Ti3Al and TiC intermetallic compounds (IMCs) and weld cracks are found in the joint without filler metals, causing the poor laser weldability. Adding V/Cu filler metals can dramatically improve the weldability of γ-TiAl alloy and steel, and detailed effects of pulse current on microstructural characterization and mechanical properties of the joints are investigated. An incomplete penetration joint is obtained when 80A is used. With the pulse current increases to 85A and 90A, full- penetration joints are obtained, and Cu-based solid solution, (Fe,V) solid solutions and less amount of AlCu2Ti IMCs are formed in the weld, but Fe2Ti is only found in the weld with 90A. The maximum joint tensile strength (297 MPa) is obtained at a pulse current of 85A, and the joints fracture at the γ-TiAl/weld interface zone where AlCuTi and AlCu2Ti IMCs are generated.