Microstructure and mechanical properties of a large billet of spray formed Al-Zn-Mg-Cu alloy with high Zn content

In this study, a large billet of Al-12Zn-2.4Mg-1.1Cu-0.5Ni-0.2Zr alloy was prepared by spray deposition technique, the billet was subsequent processed by hot extrusion, solid solution treatment at 758 K and aging at 393 K for 20 h. The aged alloy was then subjected to tensile testing, it was shown that yield strength, tensile strength and elongation rate of the alloy reached 689 MPa, 750 MPa and 11%, respectively. The composition, microstructure and fracture characteristics of the tensile sample were explored by EDS (energy dispersive spectrometer), optical microscopy (OM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. A spherical morphology of the primary α-phase was observed in the spray-deposited Al alloy, dispersed and fine-scale L12-Al3Zr phases, GPII zones and η′ precipitates, were also evident in the microstructure of the aged alloy. Fracture analysis of the tensile sample exhibited transgranular fractographic features. We suggest that precipitate-phase hardening and solid solution strengthening were responsible for reinforcing of the spray-deposited alloy.