Effect of welding on microstructure and tensile properties of flowformed Ti-6Al-4V tubes

In this study, extra-low interstitial grade Ti-6Al-4V tubes manufactured by the flowforming process were joined by plasma arc welding. Welded tubes were subjected to a stress-relief heat treatment prior to the removal of specimens for microstructural examination, and tensile and fatigue testing. Welded tubes exhibited tensile and yield strength values of 892 and 790 MPa, respectively, and elongation and reduction of area values of 7 and 30%, respectively, compared to tensile and yield strength of 1217 and 1149 MPa, respectively, and elongation and reduction of area values of 13 and 41%, respectively, of base metal. The fatigue strength of welded tubes was also 10-20% lower than that of the base metal. The significant difference in mechanical properties was attributed to microstructural changes in flowformed tubes upon welding.