Abstract:The applications of tailor friction-stirring welded blanks demand the friction stir welding (FSW) be extended to higher welding velocities. Unfortunately FSW has been traditionally applied at linear velocities less than 500 mm/min and welding parameters and thermal modeling researched and developed at low welding velocities do not directly translate to high-speed linear FSW. Therefore, to facilitate production of high volume aluminum FSW components, in this paper 7075-O aluminum alloy rolled plates of 3 mm thickness were friction stir butt welded at a constant high-travel speed of 1000 mm/min and various tool rotary speeds (1000-1900 rpm) as well as the peak temperature of joint was measured by thermal infrared camera. Effects of tool rotary speed on peak temperature and appearance and cross-sections microstructures and mechanical properties of FSW joints were investigated. The results show that peak temperature of joint increases gradually with increasing the tool rotary speed till 1600 rpm and reaches maximum at 1600 rpm,approximately 500℃. Increase of rotation speed more than 1600 rpm brought about fluctuation of peak temperature form 480 to 495℃ and slightly decreasing tendency. This does not consist with the previous thermal modeling and peak temperature function of welding parameters. With an emphasis on weld quality, the experimental results of cross-sections microstructures indicate that the optimum tool rotary speeds are 1400, 1500, 1600 rpm. Analyzing the mechanism of heat generation about friction, an analytical thermal model of high-travel FSW was developed to estimate the peak temperature in which a variable of friction was created in consideration of the properties of coefficient in the material friction.