Abstract:Underwater friction stir welding of 2219 aluminum alloy was carried out in order to further improve the joint performances by varying welding temperature history. The results indicated that the tensile strength of the joint can be improved from 324 MPa by external water cooling action in normal to 341 MPa. However, the plasticity of the joint is deteriorated. The underwater joint tends to fracture at the interface between the weld nugget zone and the thermal mechanically affected zone on the advancing side during tensile test, which is significantly different from the normal joint.

Key words: aluminum alloy; underwater friction stir welding; mechanical property