7000-series aluminum alloy extruded product and method of producing the same

Abstract

An extruded product includes a 7000-series aluminum alloy, the 7000-series aluminum alloy having an excess Mg content or an excess Zn content of less than 0.5 mass % with respect to a stoichiometric composition shown by MgZn 2 .

1 . An aluminum alloy extruded product comprising a 7000-series aluminum alloy, the 7000-series aluminum alloy having an excess Mg content or an excess Zn content with respect to a stoichiometric composition shown by MgZn 2  of less than 0.5 mass %. 
   
   
       2 . The aluminum alloy extruded product as defined in  claim 1 , the aluminum alloy extruded product having an Mg content of 0.95 to 1.95 mass % and a Zn content of 5.10 to 7.90 mass %. 
   
   
       3 . The aluminum alloy extruded product as defined in  claim 2 , the aluminum alloy extruded product having a value A indicated by a relational expression A=Zn−5.36×Mg (mass %) of −2.64 to 0.50. 
   
   
       4 . The aluminum alloy extruded product as defined in  claim 1 , an increase in proof stress due to natural aging being 15 MPa or less when comparing the proof stress of the aluminum alloy extruded product obtained by subjecting the aluminum alloy to natural aging at 50° C. or less for one week after extrusion and then subjecting the resulting product to artificial aging with the proof stress of the aluminum alloy extruded product obtained by subjecting the aluminum alloy to artificial aging immediately after extrusion. 
   
   
       5 . The aluminum alloy extruded product as defined in  claim 2 , an increase in proof stress due to natural aging being 15 MPa or less when comparing the proof stress of the aluminum alloy extruded product obtained by subjecting the aluminum alloy to natural aging at 50° C. or less for one week after extrusion and then subjecting the resulting product to artificial aging with the proof stress of the aluminum alloy extruded product obtained by subjecting the aluminum alloy to artificial aging immediately after extrusion. 
   
   
       6 . The aluminum alloy extruded product as defined in  claim 3 , an increase in proof stress due to natural aging being 15 MPa or less when comparing the proof stress of the aluminum alloy extruded product obtained by subjecting the aluminum alloy to natural aging at 50° C. or less for one week after extrusion and then subjecting the resulting product to artificial aging with the proof stress of the aluminum alloy extruded product obtained by subjecting the aluminum alloy to artificial aging immediately after extrusion. 
   
   
       7 . The aluminum alloy extruded product as defined in  claim 1 , an increase in hardness HV due to natural aging being seven or less when comparing the hardness of the aluminum alloy extruded product obtained by subjecting the aluminum alloy to natural aging at 50° C. or less for one week after extrusion and then subjecting the resulting product to artificial aging with the hardness of the aluminum alloy extruded product obtained by subjecting the aluminum alloy to artificial aging immediately after extrusion. 
   
   
       8 . The aluminum alloy extruded product as defined in  claim 2 , an increase in hardness HV due to natural aging being seven or less when comparing the hardness of the aluminum alloy extruded product obtained by subjecting the aluminum alloy to natural aging at 50° C. or less for one week after extrusion and then subjecting the resulting product to artificial aging with the hardness of the aluminum alloy extruded product obtained by subjecting the aluminum alloy to artificial aging immediately after extrusion. 
   
   
       9 . The aluminum alloy extruded product as defined in  claim 3 , an increase in hardness HV due to natural aging being seven or less when comparing the hardness of the aluminum alloy extruded product obtained by subjecting the aluminum alloy to natural aging at 50° C. or less for one week after extrusion and then subjecting the resulting product to artificial aging with the hardness of the aluminum alloy extruded product obtained by subjecting the aluminum alloy to artificial aging immediately after extrusion. 
   
   
       10 . A method of producing an aluminum alloy extruded product, the method comprising homogenizing a billet that is cast using the 7000-series aluminum alloy as defined in  claim 1  at 450 to 550° C., preheating the homogenized product at 480 to 540° C., extruding the preheated product, and subjecting the extruded product to press quenching at a cooling rate of 29° C./min or more.