Effect of Beam Oscillation on Microstructure and Tensile Property of Electron Beam-Welded Commercially Pure (CP) Titanium

In the present study, electron beam welding of commercially pure titanium has been carried out at an accelerating voltage of 60 kV, current of 40 mA, and beam speed of 900 mm/min without beam oscillation and with beam oscillation having varied oscillation diameter of 0.5-1.5 mm. The microstructure of the fusion zone shows the formation of Widmanstatten martensite and feathery alpha-titanium phase as compared to the fine acicular alpha-phase in the base metal. The phase analysis shows the presence of only the alpha-titanium phase in the fusion zone. The residual stress induced in the joint increases (1069-1366 MPa) with the increase in oscillation diameter as compared to static beam (877 MPa) and base metal (622 MPa). Due to electron beam welding without beam oscillation, there is a marginal reduction in yield strength (465-462 MPa), ultimate tensile strength (626-623 MPa), and % elongation (18.2-14%) as compared to as-received titanium. The introduction of beam oscillation of varied oscillation diameter leads to a marginal reduction in yield strength (457-452 MPa) and ultimate tensile strength (623-622 MPa), whereas, the percentage elongation increases (14-18%) with an increase in oscillation diameter as compared to the static beam. The fractography of the failed surfaces shows a mixed-mode fracture.