Microstructure and mechanical properties of Ti/steel joint welded by electron beam with adding a QCr0.8 barrier layer

Electron beam welding of TA15 titanium alloy to 304 stainless steel was carried out with a 1.5 mm thick QCr0.8 bronze barrier layer. Cross section, microstructure and mechanical properties of the joint were examined. The results show that a 0.5 mm wide unmelted QCr0.8 barrier layer exists in the weld, and thus Ti element is physically isolated from Fe to avoid the formation of Ti-Fe intermetallics. The Cu/Fe weld is characterized by solid solutions of copper and iron. As to the Ti/Cu weld, the interfacial Ti-Cu intermetallics is restricted by the addition of vanadium element, the weld is composed of solid solution of copper and (Ti, V) with a small amount of Ti-Cu compounds. Consequently, the strength and toughness of this zone are improved. The unmelted barrier layer is softened under the welding thermal cycle. Fracture occurs in the unmelted QCr0.8 alloy, with a tensile strength of 293 MPa and a plastic fracture mode.