Investigation on friction stir welding parameter design for lap joining of pure titanium

Abstract

Friction stir welding (FSW) of pure titanium lap joint using three sized tools was investigated over a wide range of welding parameters. The ranges of the welding parameters were narrow, and out of the ranges led to the emergence of welding defects, such as overheating rough surface, groove-like surface and inner cavitations. The sound joints have sufficient bonding strength in the lap zone, which insured that the fracture occurred in the base metal after a large elongation. Increasing the probe length was beneficial to widen the connection width of the lap joints. Surface polishing prior FSW reduced the inner cavitations.