Characterisation of dissimilar metal weldments of titanium alloys Ti-64 and Ti-6246 made using electron beam and rotary friction welding

Abstract Welding of dissimilar Titanium alloys viz. Ti-64 and Ti-6246 by fusion processes is challenging due to their different physical properties. Such alloys find applications in turbine disks and blades. The alloys were welded using Electron Beam Welding (EBW) and Rotary Friction Welding (RFW) processes. In this paper, metallurgical and mechanical properties of welded joints between the Titanium alloys were examined and reported. Microstructures, electron back scattered diffraction (EBSD) analysis, and residual stresses were also examined. The EBW weld was free of defects such as porosity and inclusions. Furthermore, RFW weld was also free of any defects. SEM and EBSD analysis also support this conclusion. The coarse columnar beta grains with thin needle-like alpha can be observed in the fusion zone of the EBW weldments. The grains appeared to have been refined in the deformation zone (DZ) due to dynamic recrystallization (DRX) in the RFW joints. The yield and ultimate tensile strengths of EBW weldments were 977 MPa and 1051 MPa respectively. While that of RFW weldments, 960 MPa and 1039 MPa. The percent elongation of the EBW weldments and RFW weldments was 14.2 and 10.28 respectively. The welds were stronger than the base metal in both the weldments as the fracture occurred in the Ti-64 base metal and not in the weld during tensile test. The microhardness of the fusion zone of EBW weldments was approximately 430 HV to 460 HV. While that of weld nugget of RFW weldments was 380 HV. The mechanical properties indicate that either of the welding processes is suitable for welding the alloys.