Microstructure and mechanical properties of Ti-22Al-25Nb/TA15 dissimilar joint fabricated by dual-beam laser welding

Ti-22Al-25Nb and TA15 alloys were welded by using continuous dual-beam laser welding. The effects of laser spot spacing and laser power ratio (lead/lag beam) on the appearance, microstructure, and properties of the weld joint were explored. The results showed that with an increase in laser spot spacing and laser power ratio, the width of the weld root decreases, and even the weld is lack of penetration. In addition, the content and sizes of O phases increase in the fusion zone due to the prolongation of time of B2 phase transforming into O phase and O phase growing up. The microhardness at the weld joint changed rapidly and the fusion zone showed the lowest microhardness value. A dimple fracture morphology appeared in all tensile samples. The tensile strength increased from 1001 MPa to 1011 MPa upon increasing the laser spot spacing from 0.18 mm to 0.36 mm, and the tensile strength increased from 1016 MPa to 1206 MPa with an increase in the laser power ratio from 30:70 to 40:60, except the material could not be penetrated when using a laser spot spacing of 0.54 mm or a power ratio of 50:50.