Recent Advances in Friction-stir Welding Process and Microstructural Investigation of Friction Stir Welded Pure Titanium

Abstract

The use of titanium and its alloys is increasing day by day, especially in aerospace, automobile, and de- fense fields. Friction stir welding is a prominent solid-state joining process, which produces non-melting low heat input welds with less residual stresses compared to the conventional welding process. The phys- ical and chemical properties of Ti such as low thermal expansion and thermal conductivity, relatively high melting temperature(1668℃) and high reactivity makes the FSW a favorable joining process for Ti alloys. However, Ti friction stir welds reveal highly complexed microstructure evolution in the weld zone and exhibit several defects which can influence the mechanical properties of the weld. This paper aims at a review on the microstructural evolution and typical defects formation during the FSW of CP-Ti, with the brief review on the fundamentals of friction stir welding process and Ti and its alloys.