Abstract
This study is aimed at exploring the effects of multi-stage homogenization and trace amounts of Zr and Sc on the microstructures, mechanical properties, and recrystallization of Al–4.5Zn–1.5Mg alloys. The mechanical properties of the AA7005 aluminum alloys after the T6 heat treatment were evaluated through a hardness test and tensile test. The microstructures were analyzed by an optical microscope (OM), a differential scanning calorimeter (DSC), a transmission electron microscope (TEM), a scanning electron microscope (SEM), and electron backscattered diffraction (EBSD). The results show that the grain refinement effect of the as-cast, homogenized, and recrystallized Al–4.5Zn–1.5Mg alloy containing 0.05Sc (wt%) after the T6 heat treatment was more significant than that of the alloy containing 0.1Zr (wt%). In addition, compared with the aforementioned one-stage homogenization heat treatment, the two-stage homogenization made the dispersed grain phase (Al3Zr/Al3Sc) smaller. As a result, the T6 mechanical strength of the alloy after the two-stage homogenization heat treatment was better than that of the contrastive alloy after the one-stage homogenization heat treatment. However, the two different homogenization heat treatments caused a greater divergence between the sizes of the dispersed grain phases of the Al–4.5Zn–1.5Mg alloys containing Zr than between the sizes of the dispersed grain phases of the alloys containing Sc. Therefore, after the two-stage homogenization heat treatment, the alloy with 0.1Zr (wt%) promoted the mechanical properties better than the alloy with 0.05Sc (wt%).
Highlights
The 7000 series Al–Zn–Mg (–Cu) alloy is a forged, heat-treated and high-strength aluminum alloy, which mainly achieves the precipitation strengthening effect by precipitating the second phase of the integration or semi-integration in the aluminum matrix. It is the strongest alloy among all aluminum alloys series and has high specific strength, high fracture toughness and fatigue resistance; it has been widely used in the aerospace and military industries [1,2]
The compositions of the experimental alloy samples were analyzed by the optical emission spectrometer (OES)
This study aimed to explore how multi-stage homogenization inhibits the recrystalThis study to explore how (Al–4.5ZZn–1.5Mg) multi-stage homogenization inhibits lization of theaimed commercial
Summary
The 7000 series Al–Zn–Mg (–Cu) alloy is a forged, heat-treated and high-strength aluminum alloy, which mainly achieves the precipitation strengthening effect by precipitating the second phase of the integration or semi-integration in the aluminum matrix. It is the strongest alloy among all aluminum alloys series and has high specific strength, high fracture toughness and fatigue resistance; it has been widely used in the aerospace and military industries [1,2]. Its extrusion properties are better than those of the Cu alloy, and its welding and corrosion resistance are among the best in the 7000 series alloys It is one of the main alloys for making large thin walls with high-precision complex solid or hollow structural sections. It has been commonly used as the main material for large lightweight transportation vehicles, such as the manufacture of the extruded sections and plates for high-speed train bodies [3]
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