Assessment of microstructure and tensile behavior of continuous drive friction welded titanium tubes

Friction welding process has been applied to join Grade 2 titanium alloy tubes of outer diameter 60 mm and wall thickness 3.9 mm. In this research work, five different friction times (24, 28, 32, 36 and 40 s) were used to evaluate the ultimate tensile strength (UTS) and microstructure of welded tubes. Recording of the process parameters during welding was done. Optical microscopy, electron back scattered diffraction and transmission electron microscopy were used to study the microstructure. The results showed that the friction time had a significant influence on the microstructure and UTS. The rate of deformation increased with friction time and refined the grains in the weld zone. Coarse grain structure was observed from the center of the weld zone towards the flash. Identical grain structure was observed in the heat affected zone (HAZ) and the parent metal. It was found that a maximum joint efficiency of 98.3% was achieved at a friction time of 32 s.The details of microhardness, failure location and fracture surface of the welded tubes were reported.