Microstructural evolution, tensile property and dynamic compressive property of FSWed Ti-6Al-4V alloy

Friction stir welding was applied to Ti-6Al-4V plates with 5 mm in thickness. The microstructure and mechanical properties were investigated. A full lamellar microstructure was developed near the top surface, and the size of prior beta grain gradually decreases as the distance from the top surface increases. The microstructure of the bottom is fine equiaxed alpha grains, and the mean size is 2 mu m. A mixture microstructure consisting of primary alpha, lamellar alpha + beta and fine equiaxed alpha is discovered in thermomechanically affected zone (TMAZ). Results of transverse tensile test show that the tensile strength of the joint reaches 98% that of the base material (BM). Quasi-static compression test shows that the joint exhibits larger compressive strength and failure strain than the BM. Dynamic compressive strength of the joint is close to that of the BM; furthermore, the strain at the peak stress and energy absorption of the joint are larger than those of the BM.