Texture development in Ti-6Al-4V linear friction welds

Microstructure and microtexture development in as-welded and post weld heat treated (PWHT) lab-scale (LS) and full-scale (FS) Ti-6Al-4V linear friction welds have been characterized using scanning electron microscopy and electron back-scatter diffraction (EBSD). The full-scale specimens exhibited a plastically affected zone (PAZ) about twice the size compared to lab-scale test welds. At the weld line a region of very fine martensitically formed microstructure was observed in both the LS and FS friction welds. EBSD texture scans across the weld line revealed a sharp texture variation in the PAZ. At the weld line a strong { 1 0 over(1, ̄) 0 } 〈 1 1 over(2, ̄) 0 〉 transverse texture for the as-welded and PWHTed condition was observed in both welds. Whereas the lab-scale linear friction welds displayed a dramatic change from almost random to strong transverse texture in the PAZ, the full-scale linear friction welds exhibited transverse texture at the weld line, followed by dispersed bands of transverse and { 1 1 over(2, ̄) 2 } 〈 1 1 over(2, ̄) 3 〉 type rolling texture in the PAZ region. The observed difference in LS and FS weld region textures is attributed to a difference in the variant selections during β → α transformation.