Study of the Microstructure and Properties of the Butt Joint of Laser-Welded Titanium Alloy with Flux-Cored Wire

Abstract

A self-developed Ti-Al-V-Mo system titanium alloy flux-cored wire was used to join the Ti64 titanium alloy plate via laser welding with filler wire. The microstructure and properties of the obtained welded joint were investigated. The results showed the WM (welded metal) of the welded joint consisted mainly of acicular α’ martensite, and the HAZ (heat affected zone) was comprised of a primary αp phase, Widmanstatten, and a few α’ martensite and a residual β phase. The strength and elongation of the welded joint after breaking are equivalent to that of the BM (base metal). The tensile fracture, presenting as a microvoid coalescence ductile fracture, was encompassed by massive shear lips with deep and uniform dimples. The overall microhardness of the welded joint was sequenced as WM > HAZ > BM. In the WM, large-angle grain boundaries with intragranular misorientation greater than 15° accounted for about 84%. By XRD, it was discovered the welded joint was mainly composed of the α’ martensite, with a modest amount of extremely weak multi-angle α phase diffraction peak. The test results showed the designed welding method of titanium flux-cored wire and laser wire filling is suitable for high-quality welding of titanium alloy plate.