Integral and layered mechanical properties of friction stir welded joints of 2014 aluminium alloy

Eight millimetre thick 2014-T6 Al alloy has been successfully friction stir welded. The experimental results showed that the weld tensile strength differs at different welding parameters. The maximum ultimate tensile strength, which equals to 78% that of base metal, was obtained at a rotating speed of 400 rev min^-1 and welding speed of 100 mm min^-1. For a specific welded joint, different region of the joint has different tensile strength, which depends on the microstructure variation and microhardness distribution. This is attributed to different thermomechanical actions on different regions of the joints. For the joint with three layers and without defects, the mechanical properties of middle layer are the weakest while the upper layer is the strongest. For the joints with crack or void defect, the position of the defect will be the source of fracture.