High-strength aluminum alloy extruded shape exhibiting excellent corrosion resistance, ductility, and hardenability, and method for producing the same

Abstract

An Al—Mg—Si-based high-strength aluminum alloy extruded shape exhibits excellent corrosion resistance and ductility, and exhibits excellent hardenability during extrusion (i.e., ensures high productivity). A method for producing the same is also disclosed. The high-strength aluminum alloy extruded shape includes 0.65 to 0.90 mass % of Mg, 0.60 to 0.90 mass % of Si, 0.20 to 0.40 mass % of Cu, 0.20 to 0.40 mass % of Fe, 0.10 to 0.20 mass % of Mn, and 0.005 to 0.1 mass % of Ti, with the balance being Al and unavoidable impurities, the aluminum alloy extruded shape having a stoichiometric Mg 2 Si content of 1.0 to 1.3 mass %, an excess Si content relative to stoichiometric Mg 2 Si of 0.10 to 0.30 mass %, and a total content of Fe and Mn of 0.35 mass % or more.

1 . A high-strength aluminum alloy extruded shape that exhibits excellent corrosion resistance, ductility, and hardenability, the aluminum alloy extruded shape comprising 0.65 to 0.90 mass % of Mg, 0.60 to 0.90 mass % of Si, 0.20 to 0.40 mass % of Cu, 0.20 to 0.40 mass % of Fe, 0.10 to 0.20 mass % of Mn, and 0.005 to 0.1 mass % of Ti, with the balance being Al and unavoidable impurities, the aluminum alloy extruded shape having a stoichiometric Mg 2 Si content of 1.0 to 1.3 mass %, an excess Si content relative to stoichiometric Mg 2 Si of 0.10 to 0.30 mass %, and a total content of Fe and Mn of 0.35 mass % or more. 
     
     
         2 . The high-strength aluminum alloy extruded shape as defined in  claim 1 , wherein crystal grains of the aluminum alloy extruded shape having an aspect ratio of 4.0 or more have an average crystal grain size of 80 μm or less. 
     
     
         3 . The high-strength aluminum alloy extruded shape as defined in  claim 1 , wherein the aluminum alloy extruded shape has a proof stress of 280 MPa or more. 
     
     
         4 . The high-strength aluminum alloy extruded shape as defined in  claim 1 , wherein the aluminum alloy extruded shape has an impact strength determined by a Charpy impact test of 20 J/cm 2  or more. 
     
     
         5 . A method for producing a high-strength aluminum alloy extruded shape that exhibits excellent corrosion resistance, ductility, and hardenability, the method comprising extruding an aluminum alloy, cooling the extruded aluminum alloy at an average cooling rate of 100° C./min or less immediately after the extrusion, and subjecting the cooled aluminum alloy to artificial aging, the aluminum alloy comprising 0.65 to 0.90 mass % of Mg, 0.60 to 0.90 mass % of Si, 0.20 to 0.40 mass % of Cu, 0.20 to 0.40 mass % of Fe, 0.10 to 0.20 mass % of Mn, and 0.005 to 0.1 mass % of Ti, with the balance being Al and unavoidable impurities, the aluminum alloy having a stoichiometric Mg 2 Si content of 1.0 to 1.3 mass %, an excess Si content relative to stoichiometric Mg 2 Si of 0.10 to 0.30 mass %, and a total content of Fe and Mn of 0.35 mass % or more. 
     
     
         6 . The high-strength aluminum alloy extruded shape as defined in  claim 2 , wherein the aluminum alloy extruded shape has a proof stress of 280 MPa or more. 
     
     
         7 . The high-strength aluminum alloy extruded shape as defined in  claim 2 , wherein the aluminum alloy extruded shape has an impact strength determined by a Charpy impact test of 20 J/cm 2  or more.