Effect of filler metal composition on microstructure and mechanical properties of electron beam welded titanium/copper joint

Electron beam welding of titanium to copper has been performed with different Cu-V filler metals. Microstructure, mechanical properties and fracture behavior were investigated. Compared with the welded joint without filler metal, the lower V content in Cu75V25 filler metal resulted in the formation of fine Ti-Cu compounds in the interface of TA15 side. Thus, the joint showed a lower tensile strength and fractured along the interfacial reactive layer. When V content is over 34 wt% in the filler metal, the interfacial microstructure near TA15 side formed cellular (Ti,V) solid solution to replace the Ti-Cu compounds, which improved the mechanical properties of the joint. As a result, the joint with Cu66V34 filler metal displayed the highest tensile strength (384 MPa), approaching 82% of that of the copper base metal (BM), and fractured in heat affected zone (HAZ) of copper side, due to the local softening by grains coarsening. In spite of the formed solid solution at the interface, the joint welded with Cu34V66 filler metal containing higher V content, produced amount of pores and unmelted V alloy, which resulted in the decrease of tensile strength down to 55% of that of the copper BM.