Abstract
Pulsed laser welding was used to weld dissimilar joints in Ti6Al4V/Nb alloys. The effect of heat input on the microstructural characterizations and mechanical properties of the joints was investigated. The experimental results show that underfill defects disappeared in the fusion zone (FZ) as the heat input increased. No intermetallic compounds were formed in the FZ, but a dendritic zone of Ti-rich phases and an island zone of Nb-rich phases were present for all welded joints, indicating that composition segregation occurred in the Ti6Al4V/Nb dissimilar joint. Moreover, the microstructure and mechanical heterogeneity in the FZ of the welded joint increased with increasing heat input. The microhardness of the island area was lower than that of the dendritic zone in the FZ, because it possessed higher levels of Nb. The results of the tensile tests show that the joints fractured at the Nb base metal side, suggesting that the strength of the FZ is higher than that of the Nb base metal.
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