Fracture Toughness of VPTIG Welded Joint of 2219 Al Alloy

The tension, impact and three-point bending tests were conducted on the variable polarity tangent inert gas (VPTIG) welded joint of 2219 Al alloy. Then the tensile property, impact property, fracture toughness and crack propagation process of the joint and base metal were studied and compared. The results show that the tensile strength of the welded joint was between 266 MPa and 282 MPa, which was higher than that of the base metal, and the tensile strength coefficient reached 0.6. The impact energy of the weld and heat affected zone was 7-8 J and 6-11 J, respectively, which were higher than that of the base metal. The crack tip open displacements (CTOD) in the weld were 0.056-0.124 mm with the crack extending of 0.14-0.35 mm. CTOD increased with the extension of cracks. The weld metal exhibited higher fracture toughness than the base metal. The fracture surface of the weld showed an elastic-plastic fracture feature. The crack propagation area showed dimple morphology. Some second phase particles existed in the dimples, resulting in the increase of the unstable propagation energy of the cracks.