J Langari - Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
F Kolahan - Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
K Aliakbari - Department of Mechanical Engineering, Faculty of Engineering, University of Bojnord, Bojnord, Iran

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

Friction Stir WeldingAxial ForceMechanical PropertiesMicrohardnessWeld Morphology7075 Al alloy