Microstructure and Friction and Wear Properties of Multi-pass Friction Stir Processed Zone of Commercial Pure Titanium Plates

Three-pass friction stir processing (FSP) was carried out on pure titanium plates at different rotation speeds, microstructure, hardness and friction and wear properties of friction stir processed zone were studied, and wear morphology and mechanical of the titanium plates before and after FSP were analyzed. The results show that stir zone exhibited severe plastic deformation, this resulted in a uniform recrystallized microstructure. With the increase of rotation speed, grains of stir zone were further refined. The highest hardness of 430 HV was obtained in friction stir processed zone, improved by 87% compared to 230 HV of the substrate. Average friction coefficient and wear rate of friction stir processed sample were 0.24 and 5.36×10-4 mm3·N-1·m-1. Wear mechanism of the substrate was adhesive wear, and that of friction-stir processed sample mainly was abrasive wear.