Effects of tool wear on friction stir welded joints of Ti-6Al-4V alloy

Tool wear behaviour on microstructure and mechanical properties of friction stir welded zones of Ti-6Al-4V alloy was evaluated. SEM examination, EDS analysis and X-ray diffraction results indicated that severe wear of the tool is indicated by the presence of WC-Co particles in the stir zone at rotational speed of 630 rev min(-1) and travel speed of 8 mm min(-1). Micro-hardness, tensile tests and fractographical examinations also reflected that these particles make the material more brittle and reduce the mechanical strength by 40%. However at travel speed of 22 mm min(-1), tool wear is less, hardness distribution is more uniform and enhanced ductility and strength is achieved.