A Preliminary Study of Deformation Behavior of Friction Stir Welded Ti-6Al-4V

A preliminary study of deformation behavior of friction stir welded (FSW) Ti-6Al-4V was performed using two different tools with cylindrical and stepped spiral pin design for the welding process. The nugget regions experienced temperature above β transus and the matrix transformed to fine acicular α during cooling of the nugget. By using stepped spiral pin design, a local region with much refined grain structure and significant tool debris particles were observed. Room temperature tensile test showed increased strength and decreased ductility in the material from this region. Fractographic analysis revealed that tool debris particles served as void nucleation sites. Tensile tests of FSW material were carried out at 625 °C in the strain rates of 3 × 10−4 and 1 × 10−3 s−1. The strength was higher as compared to the as-received material. Microstructural evolution during tensile test was also investigated. Results showed that dynamic globularization occurred during the high temperature tensile test.