Microstructures and mechanical properties of argon tungsten arc welded TiAl joints using Ti-Nb binary filler alloy

Argon tungsten arc welding of TiAl base alloy using Ti-30Nb (at.%) filler metals was conducted. The results indicated that sound TiAl welded joints were achieved with preheating temperature of 498 °C. Microstructure and properties of the welded TiAl joints were investigated. A transitional reaction zone, primarily consisting of γ-TiAl and α 2 -Ti 3 Al, was observed at the interface between the weld zone and the TiAl base alloy. Due to the intense reaction between the TiAl base metal and the Ti-Nb filler metal, amounts of acicular intermetallic compounds were formed within the central region of the weld zone, consisting of α 2 -Ti 3 Al and B2 phases. The tensile fracture of the joints exhibited brittle cleavage pattern. The average tensile strength of the welded joints at room-temperature reached 372.6 MPa, about 73.1 % of the base metal (BM), with joint fracture occurred in the weld zone. Owing to the solid-solution strengthening effect of Nb, the joint tensile strength retained 326.6 MPa at 700 °C, and 300 MPa at 750 °C.