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Joining of thermoplastics with friction stir welding is a quite new subject, and there are not many studies on the subject in the literature. In this study, Polyethylene and Polypropylene plates 6 mm in thickness were successfully joined by using high-speed in the CNC vertical machining center. It was determined that the increase occurring in the tool translational speed increased the welding performance depending on the temperature in the weld zone. It was determined that the increase in the tool shoulder immersion depth was effective in the fibril lengths and temperature in the joining zone, the pressure arising decreased the mechanic features by affecting the microstructure. It was observed that the increase in tool rotational speed in the weld zone increased the crystallization rate, the increase in the immersion and waiting periods at the beginning of welding and the tool shoulder immersion depth decreased the crystallization rate. In the microstructure examinations performed with the scanning electron microscope, four different microstructures were found in the weld zone. These structures were classified as: 1-The area which is not affected by the heat, 2-Joining interface, 3-Stirring zone affected thermomechanically, and 4- The zone remaining under the unjoined welding tool stirring tip part. [ABSTRACT FROM AUTHOR]

Successful joining of dissimilar materials is important in order to optimize mechanical properties such as strength, density, corrosion resistance, etc., for several applications. Al-alloys, particularly hardenable ones, are widely utilized in automobile and aerospace industries owing to their excellent properties. Besides all Al-alloys are light-weight they exhibit different properties. For instance, AA6061 alloy display excellent corrosion resistance whereas alloy AA7075 possesses a very high strength. Thus, it is worth to search the joinability of dissimilar Al-alloys plates and their performances. In this study, dissimilar Al-alloys joints (AA6061-O/AA7075-O and AA6061-T6/AA7075-T6) were produced using friction stir welding, which is well demonstrated to produce reliable joints in similar Al-alloy plates, employing two different sets of weld parameters. Detailed metallography, micro hardness measurements and tensile testing were conducted in order to characterize the joints obtained and to determine the effect of temper condition on joint performance. [ABSTRACT FROM AUTHOR]