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The microstructure of squeezing cast Al-7.8Zn-2.0Mg-1.6Cu-0.15Zr-0.18Sc alloy and those after industrial homogenization treatment and multi-stage solution treatments, were studied by differential scanning calorimetry (DSC), optical microscopy (OM), transmission electron microscope (TEM), scanning electron microscopy with energy dispersive X-ray spectroscopy (TEM-EDX). The results shows that, by complex adding the micro-alloying elements Mn, Sc, Zr, etc ,the microstructure of squeezing casting ingot are fine, uniform, equiaxed, and with the average sizes of 40 μm. The melting point of the non-equilibrium eutectic is 468 ℃ for the casting ingot. After industrial homogenization treatment at 450 ℃ for 24 h, the tensile strength of as-cast alloy is 340-350 MPa and the elongation is 3.5%-4.5%. The multi-stage solution treatment at 465 ℃, 48 h +475 ℃, 8 h +485 ℃, 2 h results in the disappearance of the non-equilibrium eutectics at grain boundary, though some phases containing Fe and Cu can not dissolve completely. After 120 ℃, 24 h aging treatment, the tensile strength is nearly 600 MPa, and the elongation improve to more than 10%.
The microstructure of squeezing cast Al-7.8Zn-2.0Mg-1.6Cu-0.15Zr-0.18Sc alloy and those after industrial homogenization treatment and multi-stage solution treatments, were studied by differential scanning calorimetry (DSC), optical microscopy (OM) , transmission electron microscope (TEM), scanning electron microscopy with energy dispersive X-ray spectroscopy (TEM-EDX). The results shows that by complex adding the micro-alloying elements Mn, Sc, Zr, etc, the microstructure of squeezing casting The melting point of the non-equilibrium eutectic is 468 ° C for the casting ingot. After industrial homogenization treatment at 450 ° C for 24 h, the tensile strength of as The multi-stage solution treatment at 465 ° C, 48 h +475 ° C, 8 h +485 ° C, 2 h results in the disappearance of the non- equilibrium eutectics at grain boundary, though some of the phases containing Fe an After 120 ℃, 24 h aging treatment, the tensile strength is nearly 600 MPa, and the elongation improves to more than 10%.