Aluminum alloy structural part, method for producing the same, and aluminum alloy sheet

Abstract

Disclosed are a structural part obtained from a 6000 series aluminum alloy sheet as a shaping raw material and having an improved crash performance; and a method for producing the sheet. For the sheet, a 6000 series aluminum alloy sheet is used which has a specified composition and is produced in the usual way. Even when this sheet is used, strain is given at a high level thereto by a cold work, thereby heightening the average dislocation density of a surface of the resultant structural part, which has been artificially aged. This density is measured by X-ray diffraction. Thus, the structural part is improved in strength and in crash performance, which is estimated in a VDA bending test, when the automobile collides.

1 . An aluminum alloy structural part excellent in crash performance, comprising Mg: 0.30 to 1.5%, and Si: 0.50 to 1.5%, the percent symbols each representing % by mass, and Al and inevitable impurities as the balance of the part; and the structural part having an average dislocation density of 3.0×10 14  to 8.0×10 14  m −2 , the density being measured by X-ray diffraction of the surface. 
     
     
         2 . The aluminum alloy structural part excellent in crash performance according to  claim 1 , further comprising Cu: 0.05 to 1.0%, the percent symbol representing % by mass; and the amount of solute Cu in a solution separated from the structural part by a residue extracting method with hot phenol being from 0.05 to 1.0% by mass of the solution. 
     
     
         3 . The aluminum alloy structural part excellent in crash performance according to  claim 1 , further comprising one or more of the following: Mn: 0.05 to 0.5%, Zr: 0.02 to 0.20%, and Cr: 0.02 to 0.15%, the percent symbols each representing % by mass. 
     
     
         4 . The aluminum alloy structural part excellent in crash performance according to  claim 1 , further comprising one or more of the following: Ag: 0.01 to 0.2%, Sn: 0.001 to 0.1%, and Sc: 0.02 to 0.1%, the percent symbols each representing % by mass. 
     
     
         5 . A method for producing an aluminum alloy structural part excellent in crash performance, comprising: applying homogenization to an aluminum alloy ingot comprising Mg: 0.30 to 1.5%, and Si: 0.50 to 1.5%, the percent symbols each representing % by mass, and Al and inevitable impurities as the balance of the ingot, and subsequently rolling the ingot into a sheet; subjecting the sheet further to solutionizing and quenching treatments, and subsequently cold-working the treated sheet to be formed into a structural part while giving a strain of 5 to 20% to the sheet; thereby adjusting the artificially aged structural part to have a dislocation density of 3.0×10 14  to 8.0×10 14  m −2 , the density being measured by X-ray diffraction of the surface. 
     
     
         6 . The method for producing an aluminum alloy structural part excellent in crash performance according to  claim 5 , wherein the aluminum alloy structural part further comprises Cu: 0.05 to 1.0%, the percent symbol representing % by mass; and the amount of solute Cu in a solution separated from the structural part by a residue extracting method with hot phenol is from 0.05 to 1.0% of the solution. 
     
     
         7 . The method for producing an aluminum alloy structural part excellent in crash performance according to  claim 5 , wherein the aluminum alloy structural part further comprises one or more of the following: Mn: 0.05 to 0.5%, Zr: 0.02 to 0.20%, and Cr: 0.02 to 0.15%, the percent symbols each representing % by mass. 
     
     
         8 . The method for producing an aluminum alloy structural part excellent in crash performance according to  claim 5 , wherein the aluminum alloy structural part further comprises one or more of the following: Ag: 0.01 to 0.2%, Sn: 0.001 to 0.1%, and Sc: 0.02 to 0.1%, the percent symbols each representing % by mass. 
     
     
         9 . The method for producing an aluminum alloy structural part excellent in crash performance according to  claim 5 , wherein the strain is given to the sheet when the sheet is formed into the structural part. 
     
     
         10 . An aluminum alloy sheet excellent in crash performance, for a structural part, comprising Mg: 0.30 to 1.5%, and Si: 0.50 to 1.5%, the percent symbols each representing % by mass, and Al and inevitable impurities as the balance of the sheet; and the following sheet having, as a microstructure, an average dislocation density of 3.0×10 14  to 8.0×10 14  m −2 , the density being measured by X-ray diffraction of the surface: a surface of the sheet which is obtained, for simulating use of the structural part, by subjecting the sheet to solutionizing treatment of keeping the sheet at 550° C. for 30 seconds, water quenching the sheet immediately down to room temperature at an average cooing rate of 30° C./s, subjecting the sheet, immediately after the quenching, to a pre-aging treatment at 100° C. for 5 hours, giving a strain of 10%, after the treatment, to the sheet through a tensile tester and further aging the sheet artificially at 210° C. for 30 minutes. 
     
     
         11 . The aluminum alloy sheet excellent in crash performance according to  claim 10 , further comprising Cu: 0.05 to 1.0%, the percent symbol representing % by mass; and the amount of solute Cu in a solution separated from the aluminum alloy sheet by a residue extracting method with hot phenol being from 0.05 to 1.0% by mass of the solution. 
     
     
         12 . The aluminum alloy sheet excellent in crash performance according to  claim 10 , further comprising one or more of the following: Mn: 0.05 to 0.5%, Zr: 0.02 to 0.20%, and Cr: 0.02 to 0.15%, the percent symbols each representing % by mass. 
     
     
         13 . The aluminum alloy sheet excellent in crash performance according to  claim 10 , comprising one or more of the following: Ag: 0.01 to 0.2%, Sn: 0.001 to 0.1%, and Sc: 0.02 to 0.1%, the percent symbols each representing % by mass.