Microstructures and Mechanical Properties of a Squeeze-Casted Al-Zn-Mg-Cu Alloy after Heat Treatment

Abstract

The effects of heat treatment on the microstructures and mechanical properties of a squeeze-casted Al-6.8%Zn-2.7%Mg-2.0%Cu alloy were studied by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It is found that squeeze casting can refine the microstructure of the alloy markedly accelerates the diffusion process of solute atoms during solution heat treatment. After solution heat treatment at 470°C for 10h and artificial aging at 130°C for 24h, the tensile strength and the elongation of the squeeze-casted alloy reach 590MPa and 5.0%, respectively, which are almost equal to those of the wrought alloy, and are significantly higher than those of the gravity-casted alloy (435MPa and 1.3%). Based on the experimental results, the mechanism of microstructural evolution and the effect of squeeze casting on the kinetics of solute diffusion and aging precipitation of the squeeze-casted Al-Zn-Mg-Cu alloy were discussed.

Non-isothermal aging of a high-Zn-containing Al–Zn–Mg–Cu alloy: Microstructure and mechanical properties

“…Al–Zn–Mg–Cu alloys (7000 series) due to high strength, low density, and good workability are extensively used in aeronautical applications [1]. These alloys are strengthened by precipitation hardening through heat treatment [2]. One of the major alloying elements in Al–Zn–Mg–Cu alloys is Zn, which has a considerable effect on the volume fraction of η′ and η (MgZn 2 ) strengthening phases.…”