Search

T-joints of an α titanium alloy were successfully welded by friction stir welding, and the evolution of microstructure, texture and mechanical properties were investigated. Results show that dynamic recrystallization occurs in the stir zone, and the grain morphology depends on whether the welding temperature exceeds β transus. The microhardness of the welded joint shows a W-shaped profile, with the highest values in the stir zone and the lowest ones in the heat-affected zone. The joint tensile strength in the skin direction is significantly higher than that in the stringer direction. As the rotation speed or the welding speed increase, the tensile strength of the joint increases to a maximum, followed by a drop in both the skin and stringer directions. Similarly, the joint impact toughness increases first and then decreases with the increase of rotational speed or welding speed. The impact fracture of the typical joint with 850 rpm-50 mm/min is ductile dominated by dimples. In addition, the corrosion resistance of welded joint is improved compared to that of the base material. • The welding temperature plays a decisive role in the final microstructure of the T-joint. • The stir zone is textured due to the dynamic recrystallization and shear action of the FSW tool. • With the increase of rotation speed, the microhardness of the joint decreases gradually. • As the rotation speed increasing, the tensile strength of the T-joint has a maximum value. • The impact toughness of the T-joint is sensitive to the rotation speed and welding speed. [ABSTRACT FROM AUTHOR]

Fracture toughness of friction stir welded titanium alloy joints was investigated using Compact tension (CT) toughness specimens. The fracture toughness slightly decreases to about 90% of the fracture toughness of base metal. The fracture surface was mainly ductile fracture mechanism with a large number of dimples. The crack propagation path was straight and mixed with intergranular and transgranular fracture. The stir zone of joint has a large number of fine ɑ grains with some dislocations. For texture, the stir zone has hard orientation {0002} <11 2 ¯ 0>, the directions of cylinder and plate thickness are parallel. The reduction of fracture toughness in the stir zone is mainly related to microstructure and texture. [ABSTRACT FROM AUTHOR]