Effect of Tool Speed on Axial Force, Mechanical Properties and Weld Morphology of Friction Stir Welded Joints of A7075-T651

The axial force measurement plays important role in tool designing and identification of its restrictions. Also, it is vital in design of machine mechanism and optimization of welding process parameters. In this study, a friction stir welded butt join on AA7075-T651 aluminum alloy plate is investigated. With change of some parameters, factors including axial force, mechanical properties, microhardness and weld morphology, are studied. For measuring axial force, load cell was utilized and a servohydraulic machine was applied to evaluate the mechanical properties. The results show that by increasing the welding speed and in the same rotational rate, the axial force and microhardness increase but the weld appearance quality decreases. However, by increasing the rotational rate in the same welding speed, there is not any certain relationship among the axial force, hardness and weld morphology. Also, by changing the tool tilt angle from zero to 2.5 degrees, the more weld morphology achieves. The results show that the change in welding speed and rotational rate have great effects in optimizing the welding friction stir process.