Microstructure and fracture path of electron beam welded joint of QCr0.8/TC4 sheet

Butted joints of sheet of QCr0.8 and TC4 were gained by electron beam welding.Microstructure and phase composition were investigated by means of optical microscope, scanning electric microscope, energy dispersive spectrometer and X-ray diffraction, as well as the tensile strength and fracture observation to discuss the fracture characteristic and path of the joints.The results showed that the weld was composed of large quantity of γ-TiCu phase, intermetallics of CuTi₂ and CuTi₃, and a small quantity of Cu-based solid solution.And beside the copper, there exists an about 20 μm thick layer of compounds, speculated to be composed of Ti₂Cu, CuTi, Cu₄Ti₃, Cu₂Ti, Cu₃Ti etc..The electron beam weldability between QCr0.8 and TC4 is dissatisfactory with focus onto the butt center line that the tensile strength is only 82.1 MPa, with cleavage fracture taking place in the coarse grain zone in weld center.