Research on Corrosion Behaviors of Electron Beam Welded Joints of TC4 Titanium Alloy in Hydrochloric Acid

Electron beam welding is more suitable for titanium alloy than traditional methods,but the corrosion behaviors of the welded joints have been rarely reported for electron beam welding,which restricts its development and applications.In this paper,the microstructure of welded joints was analyzed by metallography,electron microscopy and X-ray diffraction.Meanwhile,the corrosion resistance and corrosive behaviors of the overall welded joint,welding bead and base metal in 1 mol/L HCl medium were investigated by electrochemical method.The results show that the base material of the welded joint consists of the equiaxed α phase and the β phase in the gap,and the heat affected zone is composed of the original α phase,β phase and α’ phase,while the weld bead is under the structure of α’ phase only.The corrosion resistance of the weld bead is better than that of the base metal,and the corrosion resistance of the overall welded joint is worse than that of the base metal.With immersion time increasing,all samples undergo active dissolution,passivation film generation and destruction processes.After immersion,the surface of the samples is etched,the corrosion resistance decreases sharply.