High-strength aluminum alloy thin extruded shape and method for producing the same

Abstract

An Al—Zn—Mg—Cu-based high-strength aluminum alloy thin extruded shape has a yield strength of 700 MPa or more. The high-strength aluminum alloy thin extruded shape includes 9.0 to 13.0 mass % of Zn, 2.0 to 3.0 mass % of Mg, 1.0 to 2.0 mass % of Cu, and 0.05 to 0.3 mass % of Zr, with the balance being Al and unavoidable impurities, fine precipitates having a circle equivalent diameter of 5 to 20 nm being dispersed in a crystal grain of the extruded shape in a number of 4000 to 6000 per μm 2 .

1 . A high-strength aluminum alloy thin extruded shape comprising 9.0 to 13.0 mass % of Zn, 2.0 to 3.0 mass % of Mg, 1.0 to 2.0 mass % of Cu, and 0.05 to 0.3 mass % of Zr, with the balance being Al and unavoidable impurities, fine precipitates having a circle equivalent diameter of 5 to 20 nm being dispersed in a crystal grain of the extruded shape in a number of 4000 to 6000 per μm 2 . 
     
     
         2 . The high-strength aluminum alloy thin extruded shape according to  claim 1 , the high-strength aluminum alloy thin extruded shape having a yield strength of 700 MPa or more and an elongation of 9% or more. 
     
     
         3 . A method for producing a high-strength aluminum alloy thin extruded shape comprising casting an aluminum alloy to obtain an ingot, subjecting the ingot to homogenization and hot extrusion to obtain a hot-extruded shape, and subjecting the hot-extruded shape to a solution treatment, a quenching treatment, and an aging treatment, the aluminum alloy comprising 9.0 to 13.0 mass % of Zn, 2.0 to 3.0 mass % of Mg, 1.0 to 2.0 mass % of Cu, and 0.05 to 0.3 mass % of Zr, with the balance being Al and unavoidable impurities, and the aging treatment including a first-stage aging treatment, a second-stage aging treatment, and a third-stage aging treatment, the first-stage aging treatment holding the hot-extruded shape at 100 to 130° C. for 6 to 48 hours, and cooling the hot-extruded shape to room temperature, the second-stage aging treatment heating the hot-extruded shape to 160 to 180° C. at a temperature increase rate of 0.5° C./sec or more, holding the hot-extruded shape at 160 to 180° C. for 10 X  to 10 Y  minutes, and cooling the hot-extruded shape to room temperature at a cooling rate of 0.02° C./sec or more, and the third-stage aging treatment holding the hot-extruded shape at 100 to 130° C. for 6 to 48 hours, and cooling the hot-extruded shape to room temperature, provided that X=−0.03×holding temperature+5.11, and Y=−0.03×holding temperature+7.07.