The joining of CP-vanadium and Ti–6Al–4V using the Electron Beam Melting Additive Manufacturing method

Abstract

The use of electron beam welding for dissimilar welding (DW) of commercially pure (CP) vanadium to Ti–6Al–4V has been investigated via ARCAM S12, an additive manufacturing powder-bed system. Investigations of bead-on-plate welds for Ti–6Al–4V were first conducted to identify the process parameters for full penetration welds with a minimum energy input of 37 mA at a traverse speed of 7 mm/s. Vanadium bead on plate welds produced a penetration of approximately 75%, which was enough to proceed onto DW experiments. Defect-free full penetration welds were produced. The DW weld zone microstructure revealed an elongated dendritic structure comprised of bulky βTi grains and a fine substructure of α' laths. Thermal imaging (TI) showed an increment in radiance temperature ahead of the melt pool, indicating that there is a minimum energy required before keyhole welding is present, confirming mathematical calculations. Mechanical characterisation finds a fair range of hardness across both base metals (BM), heat affected zones (HAZ) and fusion zones (FZ). With no yield plateau in tensile test curves, the material is confirmed to fail on the side with lower mechanical properties, i.e., vanadium, which draws a fair process window for dissimilar welding between Ti6Al4V and vanadium alloys.