Effect of tool shape on mechanical properties and microstructure of friction stir welded aluminum alloys

Prospecting the optimal tool design for welding steels, the effect of the tool shape on the mechanical properties and microstructures of 5-mm thick welded aluminum plates was investigated. The simplest shape (column without threads), the ordinary shape (column with threads) and the triangular prism shape probes were used to weld three types of aluminum alloys. For 1050-H24 whose deformation resistance is very low, a columnar tool without threads produces weld with the best mechanical properties; for 6061-T6 whose deformation resistance is relatively low, the tool shape does not significantly affect the microstructures and mechanical properties. For 5083-O whose deformation resistance is relatively high, the weldablity is significantly affected by the rotation speed. For a low rotation speed (600 rpm), the tool shape does not significantly affect the microstructures and mechanical properties of the joints.