Microstructure and mechanical properties of laser welded Ti–22Al–27Nb/TC4 dissimilar alloys

Laser welding was applied to join 2.5 mm thick dissimilar metals of Ti–22Al–27Nb (at%) alloy and TC4 (Ti–6Al–4V, wt%) alloy. The microstructure characterization and the mechanical properties of the laser welded joints were investigated. The results show that a well-quality joint can be obtained using laser welding method. The B2 phase and a little residual coarse α2 phase are formed in heat affected zone (HAZ) of Ti–22Al–27Nb alloy. The heat affected zone of TC4 alloy mainly consists of a mixture of martensitic α′, acicular α, and primary α phase. The weld metal is mainly composed of B2 phase and martensitic α′ phase. The microhardness values of heat affected zone are higher than that of fusion zone (FZ) and the base metal. And the fusion zone exhibits the lowest microhardness values in the welded joint. The average tensile strength of the joints can reach about 92% of the TC4 parent metal, but the elongation of the joints is found to be less than 40% of the TC4 parent metal.