High-strength aluminum alloy extruded material and manufacturing method therefor

Abstract

An aluminum alloy extruded material including: Zn: 7.5 to 9.2% by mass; Mg: 1.3 to 2.0% by mass; Cu: 0.1 to 0.7% by mass; one or more elements selected from the group consisting of Mn: 0.30% by mass or less, Cr: 0.25% by mass or less, and Zr: 0.25% by mass or less, totaling 0.1 to 0.5% by mass; and Ti: 0.005 to 0.20% by mass, and Al. An average spacing of grain boundary precipitates is 0.8 to 1.4 μm, an average particle length of the grain boundary precipitates is 0.3 to 0.5 μm, and a proof stress is 440 N/mm 2 or more.

1 . An aluminum alloy extruded material comprising:
 Zn: 7.5% to 9.2% by mass;   Mg: 1.3% to 2.0% by mass;   Cu: 0.1% to 0.7% by mass;   at least one element selected from the group consisting of Mn: 0.30% by mass or less, Cr: 0.25% by mass or less, and Zr: 0.25% by mass or less: totaling 0.1% to 0.5% by mass;   Ti: 0,005% to 0.20% by mass; and   Al,   wherein an average spacing of grain boundary precipitates is 0.8 μm to 1.4 μm, and an average particle length of the grain boundary precipitates is 0.3 μm to 0.5 μm, and a proof stress is at least 440 N/mm 2 .   
     
     
         2 . The aluminum alloy extruded material according to  claim 1 , wherein the average spacing of the grain boundary precipitates is 1.2 μm or less. 
     
     
         3 . A method for manufacturing an aluminum alloy extruded material, the method comprising:
 soaking an aluminum alloy comprising:
 Zn: 7.5% to 9.2% by mass, 
 Mg: 1.3% to 2.0% by mass, 
 Cu: 0.1% to 0.7% by mass, 
 at least one element selected from the group consisting of Mn: 0.30% by mass or less, Cr: 0.25% by mass or less, and Zr: 0.25% by mass or less: totaling 0.1% to 0.5% by mass, 
 Ti: 0.005% to 0.20% by mass, and 
 Al; 
   hot-extruding the aluminum alloy after the soaking;   cooling the aluminum alloy at a temperature from 400° C. to 300° C. at an average cooling rate of from 100° C./minute to 600° C./minute during cooling after the hot-extruding; and   applying artificial aging treatment to the aluminum alloy after the cooling.   
     
     
         4 . The method for manufacturing an aluminum alloy extruded material according to  claim 3 , wherein the cooling after the hot-extruding is performed by die quenching. 
     
     
         5 . The aluminum alloy material according to  claim 1 , wherein the content of Zn is from 8.0% to 9.0% by mass. 
     
     
         6 . The aluminum alloy material according to  claim 1 , wherein the content of Mg is from 1.4% to 1.8% by mass. 
     
     
         7 . The aluminum alloy material according to  claim 1 , wherein the content of Cu is from 0.2% to 0.5% by mass. 
     
     
         8 . The aluminum alloy material according to  claim 1 , wherein the content of Zr is from 0.12% to 0.23% by mass. 
     
     
         9 . The aluminum alloy material according to  claim 1 , wherein the content of Cr is from 0.1% by mass or less. 
     
     
         10 . The aluminum alloy material according to claim content of Mn is from 0.1% by mass or less. 
     
     
         11 . The aluminum alloy material according to  claim 1 , wherein the content of Ti is from 0.01% by mass to 0.05% by mass. 
     
     
         12 . The aluminum alloy material according to  claim 1 , wherein the average spacing of grain boundary precipitates is from 0.8 μm to 1.2 μm. 
     
     
         13 . The method according to  claim 3 , the method further comprising:
 homogenizing the aluminum alloy at a temperature of from 490° C. to 550° C. for 4 to 10 hours.   
     
     
         14 . The method according to  claim 3 , the method further comprising:
 homogenizing the aluminum alloy at a temperature of from 500° C. to 540° C. for 4 to 10 hours.   
     
     
         15 . The method according to  claim 3 , the method further comprising:
 homogenizing the aluminum alloy at a temperature of from 510° C. to 530° C. for 4 to 10 hours.   
     
     
         16 . The method according to  claim 3 , wherein the hot-extruding is performed at an extrusion temperature of from 450° C. to 510° C. at an extrusion speed of 2 m/min to 15 m/min. 
     
     
         17 . The method according to  claim 3 , wherein the aluminum alloy is cooled from 400° C. to 200° C. at an average cooling rate of from 100° C./minute to 600° C./minute during cooling after the hot-extruding. 
     
     
         18 . The method according to  claim 3 , wherein the applying artificial aging treatment further comprises:
 holding at a temperature of 65° C. to 95° C. for 2 to 6 hours; and then   holding at a temperature of 120° C. to 170° C. for 6 to 15 hours.   
     
     
         19 . The aluminum alloy material according to  claim 1 , wherein the content of Zn is from 8.1% to 9.8% by mass. 
     
     
         20 . The aluminum alloy material according to  claim 1 , wherein the content of Zr is from 0.14% to 0.20% by mass.