Influence of second phases on mechanical properties of spray-deposited Al–Zn–Mg–Cu alloy

Al–10.66Zn–2.48Mg–1.41Cu–0.17Zr–0.17Sc (wt.%) alloy prepared by spray deposition was processed with different hot deformation followed by heat treatment. The mechanical properties and microstructure evolution were investigated. The results indicate that uniform ultimate tensile strength of 774 MPa, yield strength of 734 MPa and elongation of 13.7% are obtained with two-step hot deformation, which increase by 2.7%, 3.82% and 95% compared with one-step hot deformation. Microstructural observations show that increase of elongation is mainly ascribed to high volume fraction of smaller precipitates and reduction of stress concentration areas as a result of disappearance of the coarse second phases. The fractured tensile specimens with two-step hot deformation exhibit dimple fractographic features. Improvement of strength is attributed to the precipitation strengthening and dispersed strengthening.

► High strength and high ductility of Al–Zn–Mg–Cu alloy is prepared successfully. ► Second phases dissolve completely into α-Al matrix after two-step hot deformation. ► Reduction of stress concentration areas contribute to increase in elongation. ► High volume fraction of small precipitates can also increase elongation. ► Both precipitation and dispersed strengthening lead to increase in strength.