Heterogeneous Deformation Behaviors of an Inertia Friction Welded Ti₂AlNb Joint: an In-situ Study

A defect-free Ti₂AlNb joint has been obtained by the inertia friction welding (IFW) technology. The weld zone (WZ) is composed of B2 grains refined by discontinuous dynamic recrystallization and enhanced by grain refinement strengthening. And the average microhardness decreases by about 30 HV from the WZ to the base metal. In-situ SEM analysis reveals that the heterogeneous structure of the joint causes strong strain partitioning during tensile deformation. The microcrack initiation occurs at the interface of the initial B2 phases and B2/O boundaries. Owing to stress concentration, the multi-slip bands and cracks tend to generate in the heat-affected zone (HAZ), causing a premature fracture.