Better mechanical properties via uniform microstructure architecture in flash-butt welded TA19 joints

Abstract

Both ductility and strength are simultaneously improved via the tailoring of uniform microstructure in a flash-butt welded TA19 joint that is subjected to an appropriate post-weld heat treatment (PWHT). The PWHT sample exhibits almost the same ductility (i.e., elongation and reduction in area) as the matrix that was treated at the same conditions. Such uniform microstructural characteristics, including relief of tensile residual stress, formation of large α grains at the welding seam, dissolution of a continuous α phase at the grain boundary, recrystallization and moderate growth of primary α (αp) at the thermo-mechanically affected zone, and recovery, recrystallization and significant growth of αp grains in the stress-affected zone, are responsible for at least ~25% of the ductility improvement. Also, the increase in strength stems mainly from age hardening of the matrix that accounts for ~90% of the material volume at the gauge length. This paper provides a guideline for microstructural architecture that has desirable uniformity in other welded Ti alloys to maintain high performance.