Abstract: The 2519-T87 high strength aluminum alloy is welded to study the impact properties and microstructure of the joints. Results indicate that the lower impact toughness of weld centre zone and fusion line zone is caused by the network distribution of α+θ (CuAl2) eutectic phase along the grain boundary. And the higher amount of eutectic phase is in the equiaxed zone along fusion line, which makes it have the poorest impact toughness. The local melting and microfissure are the main cause for the embrittlement of partially melted zone. The value of the impact absorbed energy in the full-reverted region reaches the maximum 22 J because of the dissolution of precipitates, whereas that value in overaged zone is only 7 J because of coarsening of precipitates. Fractography shows that the fracture of partially melted zone is brittle intergranular fracture, and those of other zones are dimple fractures. The dimples in the fracture of the fully reverted zone are the deepest, and there are least particles in them.

Key words: Heat affected zone, High strength aluminum alloy, Impact toughness, Microstructure