Aluminum alloy sheet

Abstract

A 7xxx-series aluminum alloy sheet produced by a common procedure is allowed to include a surface part having a texture with grown Cube orientation, and a central part having a texture with grown S orientation. Namely, the surface part and the thickness-central part in the sheet are allowed to have different textures that are optimal respectively for shock absorption and for strength. This allows the aluminum alloy sheet to have better shock absorption upon automobile collision without lowering its strength, where the shock absorption is evaluated by a VDA bend test as illustrated in FIG. 1.

1 . An aluminum alloy sheet, comprising: in mass percent,
 Zn in a content of 2.0% to 9.0%;   Mg in a content of 0.5% to 4.5%;   Cu in a content of 0.5% or less;   Zr in a content of 0.15% or less;   Mn in a content of 0.2% or less;   Cr in a content of 0.15% or less;   Sc in a content of 0.05% or less; and   wherein   the aluminum alloy sheet includes a surface part ranging from a sheet surface to a depth of 15% of a sheet thickness and a thickness-central part,   contains grains with Cube orientation and grains with S orientation, an area percentage of the grains with Cube orientation of all grains in the surface part is represented by [surface part Cube], and an area percentage of the grains with S orientation of all grains in the surface part is represented by [surface part S],   the thickness-central part contains grains with Cube orientation and grains with S orientation, an area percentage of the grains with Cube orientation of all grains in the thickness-central part is represented by [thickness-central part Cube], and an area percentage of the grains with S orientation of all grains in the thickness-central part is represented by [thickness-central part S],   the surface part comprises an equiaxial recrystallized microstructure having an average grain size of 40 μm or less, and   the surface part and the thickness-central part have such different textures that:
 the [surface part Cube] is 10% or more; 
 the [surface part S] is 10% to 40%; 
 a ratio of the [surface part Cube] to the [thickness-central part Cube] is greater than 1.0; and 
 a ratio of the [surface part S] to the [thickness-central part S] is less than 1.0. 
   
     
     
         2 . The aluminum alloy sheet according to  claim 1 , further comprising: at least one of (a) and (b), in mass percent:
 (a) at least one of:
 Ag in a content of 0.01% to 0.2%, and 
 Sn in a content of 0.001% to 0.1%; and 
   (b) Ti in a content of 0.001% to 0.1%.   
     
     
         3 . A shock absorber, comprising
 the aluminum alloy sheet according to  claim 1 .   
     
     
         4 . A shock absorber, comprising
 the aluminum alloy sheet according to  claim 2 .