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Phases and microstructures of three high Zncontaining Al–Zn–Mg–Cu alloys were investigated by means of thermodynamic calculation method, optica microscopy(OM), scanning electron microscopy(SEM)energy dispersive spectroscopy(EDS), X-ray diffraction(XRD), and differential scanning calorimetry(DSC) analysis. The results indicate that similar dendritic network morphologies are found in these three Al–Zn–Mg–Cu alloys. The as-cast 7056 aluminum alloy consists of aluminum solid solution, coarse Al/Mg(Cu, Zn, Al)_2 eutectic phases, and fine intermetallic compounds g(MgZn_2). Both of as-cast 7095 and 7136 aluminum alloys involve a(Al)eutectic Al/Mg(Cu, Zn, Al)_2, intermetallic g(MgZn_2), and h(Al_2Cu). During homogenization at 450 °C, fine g(MgZn_2) can dissolve into matrix absolutely. After homogenization at 450 °C for 24 h, Mg(Cu, Zn, Al)_2 phase in 7136 alloy transforms into S(Al_2Cu Mg) while no change is found in 7056 and 7095 alloys. The thermodynamic calculation can be used to predict the phases in high Zncontaining Al–Zn–Mg–Cu alloys.
Phases and microstructures of three high Zncontaining Al-Zn-Mg-Cu alloys were investigated by means of thermodynamic calculation method, optica microscopy (OM), scanning electron microscopy (SEM) energy dispersive spectroscopy (EDS) , and differential scanning calorimetry (DSC) analysis. The results that similar dendritic network morphologies were found in these three Al-Zn-Mg-Cu alloys. The as-cast 7056 aluminum alloy consists of aluminum solid solution, coarse Al / Mg Cu, Zn, Al) 2 eutectic phases, and fine intermetallic compounds g (MgZn_2). Both as-cast 7095 and 7136 aluminum alloys involve a (Al) eutectic Al / Mg After homogenization at 450 ° C for 24 h, Mg (Cu, Zn, Al) _2 phase in 7136 alloy (MgZn_2) was homogenized at 450 ° C, transforms into S (Al_2Cu Mg) while no change is found in 7056 and 7095 alloys. The thermodynamic calculation can be used to predict the phases in high Zncontaining Al-Zn-Mg-Cu alloys.