Microstructure and mechanical properties of electron beam welded TC4 titanium alloy structure with backing plate

This study investigates the microstructure characterization and residual stress differences of a welded TC4 titanium alloy structure to determine the optimum electron beam welding parameters. A finite element model is constructed on the basis of the actual weld morphology under different welding parameters, and the Mises stress of the titanium alloy electron beam joint is compared. The residual stress distribution in the shell structure with a backing plate under superimposed working stress conditions is analyzed. Results show that the change of microstructure and mechanical properties of each area do not show remarkable changes with variations in welding speed. However, the macroscopic morphology varies greatly, and the microhardness and maximum shear strength distribution appears as follows: the weld metal > heat affected zone > base metal. The finite element simulation reveals that the peak residual stress of WM along the longitudinal and transverse directions is 782 MPa and 583 MPa respectively, which is consistent with the distribution of the measured results. The finite element calculation results of the shell structure under internal pressure show that the Mises stress of the WM appears the smallest value when the welding speed reaches 8 mm/s, and its value is 650.59 MPa. Therefore, a smaller the welding speed (from 14 mm/s to 8 mm/s) of the shell structure has a positive effect on service behavior.