Enhanced SCC resistance of 7056 aluminium alloy by Y and Si additions

The effect of Y and Si additions on the microstructure and stress corrosion cracking (SCC) of the high Zn-containing 7056 aluminium alloy has been investigated. The morphology and composition of dispersions were analysed by transmission electron microscope equipped with super-X energy disperse spectroscopy. The SCC resistance was measured by a double-cantilever beam experiment. Results indicated that the SCC resistance was significantly improved by the mixed Y and Si additions, which can mainly be attributed to the reduction in the recrystallisation fraction and the increase in the sub-grain boundaries fraction caused by the high coherent (Al,Si) 3 (Zr,Y) dispersions and another important reason was the formation of the Y–Si-containing oxide film with the higher compactness and electrochemical impedance.