Influencing mechanisms of weld root tip on microstructure and mechanical properties of electron beam welded joints of titanium alloy thick plates

The welding of titanium alloy thick plates often formed a narrow weld seam in the weld root, named as ‘weld root tip’, because of insufficient fusion, which could reduce the joint properties. In this study, 30 mm-thick Ti-5Al-5Mo-5V-1Cr-1Fe alloy was butt welded via electron beam welding to reveal the influencing mechanisms of the weld root tip on joint microstructure and mechanical properties. The subparallel or parallel weld seam with the weld angles of 0°–3° between the centre line and edge of the fusion zone removed the weld root tip, achieving almost the same mechanical properties with those of the welding zone.