TWI

Microstructural and textural variations in friction stir weld-affected regions of near-alpha Ti-5111 alloys (Ti, 5%Al, 1%Sn, 1%Zr, 1%V, 0.8%Mo) were investigated experimentally and a model incorporating micro-shear banding was proposed to account for differences in morphology, microstructure and texture evolution within the banded regions. Weldments were fabricated as bead-on-plate specimens or by joining two plates (thickness 7.16 mm) using a truncated conical tool at rotational speeds of 140 or 225 rpm and travel speeds of 25.4-101.6 mm/min. Welded joint microstructure was observed by optical microscopy, SEM and electron backscatter diffraction. The beta grain structure present at the welding temperature was calculated from measured alpha-phase data using the equations of Glavicic et al. (2003). The microstructural characteristics of HAZ, thermomechanically affected zones and stir zone are discussed and a microstructural evolution mechanism is described.

9th International Symposium, 15-17 May 2012, Session 6B: High Temperature FSW I, Paper 01