Electron Beam Welding Of Dissimilar Materials Between QCr0.8 And TC4

Electron beam welding (EBW) of dissimilar materials between chromium bronze and Ti-6Al-4V alloy in thin plates was investigated in this paper. To improve the non-uniform heat conduction and fusion of dissimilar materials on both sides, deflection electron beam welding technology was brought out and to control the joints microstructure, and generation and distribution of the intermetallics in the interface of the base metal (BZ), so that to improve the mechanical properties of the joints. Mechanism, phase composition and effects of the defecting distance to copper side (h_c) and welding parameters on the microstructure and mechanical properties of the joints, were investigated by optical microscope, scanning electric microscope, energy dispersive spectrometer and X-ray diffraction, as well as the fracture path and mechanism of the joints.Because of large quantities of intermetallics, such as CuTi₃, CuTi and Cu₂Ti, generating in the joint, electron beam welded joints between QCr0.8 and TC4 under condition of focusing onto butt center line showed that the tensile strength was quite low which was only 82.1MPa. The deflection electron beam welding procedure well performed on controlling the joint structure which made the weld composed of large quantities of Cu-based solid solution, and the strength of EBW joints with focus on copper side was increased the maximum of which was achieved up to 270.5MPa. For the joint welded with focus onto the butt center line cleavage fracture took place on the weld center of, as well as quasi-cleavage fracture on the interface of the BZ for all the other joints welded with focus on copper side.The analysis of the joints microstructure showed that the weld zones were divided into two typical zones, namely fusion zone (FZ) and reaction zone (RZ) between FZ and TC4, regardless of the changes of h_c or welding parameters. The FZ of the deflection beam welded joint was composed of Cu-based solid solution as base microstructure with intermetallics distributed on it, but CuTi3-based solid solution of the welded joints with focus on the butt center line. And the RZ was composed of Cu+Cu_xTi zone and CuTi-based solid solution zone. The effects of the welding parameters on the generation and growth of the reaction layer that were elementarily analyzed, were investigated to represent the relationships among the welding parameters, reaction layer structure and mechanical properties of the joints.