Microstructure and mechanical properties of flash-butt welded two-phase Ti–6Al–2Sn–4Zr–2Mo (Ti6242) alloy are investigated. High ductility that is at least comparable to that of the matrix and extra strain hardening are achieved in welded joints because of the formation of a particular semi-equiaxed structure in the double-affected zone (DAZ). Also, no strength loss is observed, and this is attributed to a uniform hardness distribution in a narrower welding zone. The soft DAZ, which is sandwiched between the welding seam and stress-affected zone, enables better deformation compatibility among these zones, and weakens their stress concentration. Furthermore, such semi-equiaxed structure effectively suppresses the formation of dense slip bands and crack nucleation and provides a strong barrier against its propagation. This work provides a new understanding of this particular microstructure, which is expected to have a higher combination of strength and ductility in Ti alloys.

研究了闪光对焊两相Ti–6Al–2Sn–4Zr–2Mo（Ti6242）合金的组织和力学性能。由于在双影响区（DAZ）中形成了特定的半等腰结构，因此在焊接接头中可实现至少与基体相当的高延展性和额外的应变硬化。另外，没有观察到强度损失，这归因于在较窄的焊接区域中均匀的硬度分布。夹在焊缝和受应力影响区域之间的软DAZ，可使这些区域之间具有更好的变形相容性，并减弱其应力集中。此外，这种半等距结构有效地抑制了致密滑带的形成和裂纹成核，并为其传播提供了强大的屏障。