MECHANICAL BEHAVIOR OF FRICTION STIR SPOT WELDING OF ALUMINUM ALLOY 6063-T5

Abstract

This article studies the mechanical behavior of Friction Stir Spot Welds, FSSW, in AA6063-T5 aluminum sheets, conducted on a universal milling machine and in a special machine for this welding technique. The microstructure analysis of the welded joints, allowed the correlation between the micro structural changes, caused by the thermal effects and the plastic deformation of the welding process, with the mechanical properties found in the welds. Additionally, the static behavior of the FSSW joints together with rivets was compared. The results showed that the tensile behavior of the welded joints exceeds in 100 % that of the riveted joints, showing an interfacial fracture type of failure. The values of microhardness in the heat affected zone are comparable with  those  of  the base metal and show  a  drastic  reduction  in  the thermo-mechanically affected zone that  facilitates  the fault condition under  static load. Micro structural analysis shows a grain refinement of 90 % in the stirred zone related to the base metal, explaining the higher microhardness values in this zone. It was found  a small  increase in the  mechanical  behavior of  welds made  in   the standard machine compared to those in the universal milling machine assigned to the better control of process parameters.