High-strength aluminum alloy sheet

Abstract

An Al—Mg—Si aluminum alloy sheet has a chemical composition which includes at least one element selected from the group consisting of Mn, Cr, and Zr and which meets the condition: 0.6≤([Mg]/[Si]-0.15[Mn]-0.3[Cr]-0.1[Zr]≤1.8. The aluminum alloy sheet is controlled to have a higher aspect ratio of grains, thereby has significantly higher strength after artificial aging such as paint bake (after bake hardening), and satisfactorily has strength necessary for automobile structural components, without deterioration in bendability.

1 : A high-strength aluminum alloy sheet comprising, in mass percent:
 Mg in a content of 0.6% to 2.0%;   Si in a content of 0.6% to 2.0%;   at least one element selected from the group consisting of Mn, Cr, and Zr in a total content of 0.2% to 1.0%,   Al and unavoidable impurities,   wherein the contents of Mg, Si, Mn, Cr, and Zr satisfy a condition represented by:
   0.6≤[Mg]/([Si]-0.15[Mn]-0.3[Cr]-0.1[Zr])≤1.8
 
   wherein [Mg], [Si], [Mn], [Cr], and [Zr] are contents in mass percent respectively of Mg, Si, Mn, Cr, and Zr,   wherein the aluminum alloy sheet has a D1 of 100 μm or less and an aspect ratio D1/D2 of 3.0 to 10.0,   where D1 is an average length of major axes of grains in an area of 1000 μm by 1000 μm as observed by SEM-EBSD in a cross section parallel to the sheet rolling direction; and D2 is an average length of minor axes of the grains.   
     
     
         2 : The high-strength aluminum alloy sheet according to  claim 1 , further comprising at least one element selected from the group consisting of:
 Cu in a content of 0.05% to 0.5%;   Ag in a content of 0.01% to 0.2%; and   Sn in a content of 0.005% to 0.3%.   
     
     
         3 : The high-strength aluminum alloy sheet according to  claim 1 , comprising Mn. 
     
     
         4 : The high-strength aluminum alloy sheet according to  claim 1 , comprising Cr. 
     
     
         5 : The high-strength aluminum alloy sheet according to  claim 1 , comprising Zr. 
     
     
         6 : The high-strength aluminum alloy sheet according to  claim 1 , comprising Mn and Cr. 
     
     
         7 : The high-strength aluminum alloy sheet according to  claim 1 , comprising Mn and Zr. 
     
     
         8 : The high-strength aluminum alloy sheet according to  claim 1 , comprising Cr and Zr. 
     
     
         9 : The high-strength aluminum alloy sheet according to  claim 1 , comprising Mn, Cr and Zr. 
     
     
         10 : The high-strength aluminum alloy sheet according to  claim 2 , comprising Cu. 
     
     
         11 : The high-strength aluminum alloy sheet according to  claim 2 , comprising Ag. 
     
     
         12 : The high-strength aluminum alloy sheet according to  claim 2 , comprising Sn. 
     
     
         13 : The high-strength aluminum alloy sheet according to  claim 2 , comprising Cu and Ag. 
     
     
         14 : The high-strength aluminum alloy sheet according to  claim 2 , comprising Cu and Sn. 
     
     
         15 : The high-strength aluminum alloy sheet according to  claim 2 , comprising Ag and Sn. 
     
     
         16 : The high-strength aluminum alloy sheet according to  claim 2 , comprising Cu, Ag and Sn.