Influence of vanadium filler on the properties of titanium and steel TIG welded joints

Fusion bonding of TiTi, FeFe and Ti/FeTi/Fe butt-welded joints through vanadium filler metal was investigated. Tungsten inert gas (TIG) welding method was employed. The microstructures of the welded joints were analyzed by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Mechanical properties of the joints were evaluated by microhardness tests and tensile tests. Vanadium exhibited good bonding with adjacent materials in Ti-Ti and Fe-Fe welded joints. Continuous solid solutions were observed in both Ti-Ti and Fe-Fe joints. Ti-V-Ti and Fe-V-Fe welds exhibited the average tensile strength of 416 MPa and 434 MPa, respectively. Vanadium, ER50-6 and ERTi-1 filler metals were applied to join Ti/Fe bimetallic sheet. Serious cracks were observed in the joint. XRD pattern of the fractured surface confirmed the Fe2Ti and σ intermetallics. The regions dominated by Fe-Ti compounds exhibited high hardness values (∼1112HV0.01). Cracks initiated and propagated in regions rich in Fe-Ti and σ intermetallic phases. The magnitude and distribution of welding residual stresses were estimated by finite element method. The peak Von Mises stresses (Ti-V-Ti, 501 MPa; Fe-V-Fe, 555 MPa) occurred in the base metals near V welds. The brittle intermetallics and high thermal induced stresses resulted in the cracking in Ti/Fe-Ti/Fe welded joint.