On the role of axial load and the effect of interface position on the tensile strength of a friction stir welded aluminium alloy

This investigation highlights the influence of axial load, and the effect of position of the interface with respect to the tool axis on tensile strength of the friction stir welded joint. The axial load is continuously varied by linearly increasing the interference between the tool shoulder and the surface of the base material. The interface position with respect to the tool axis is continuously changed by keeping the feed direction at an angle to the interface. The base material used in this study is Al–Zn–Mg alloy, 7020-T6, of 4.4 mm thickness. It is found that there is an optimal axial load, above which the weld is defect-free, with joint efficiency of 84%. There is a tolerance for interface position; i.e., the tool can be allowed to deviate away from the interface without deteriorating joint efficiency of the weld. The tool can be allowed to deviate from the interface in either side, but the tolerance is higher when the interface is located in the advancing side of the tool.