Flash-butt welded Ti6242 joints preserved base-material strength and ductility

Abstract 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.