Aluminum alloy sheet for vehicle structural component and method of manufacturing the aluminum alloy sheet

Abstract

Provided is a 6000-series aluminum alloy sheet suitable for a vehicle structural component. The Mg content and the Si content of an Al—Mg—Si aluminum alloy sheet are balanced in a special relationship, particularly cube orientation is increased as a texture in a surface region of the sheet, and the yield ratio of the sheet is reduced, thereby high strength of 0.2% proof stress of 220 MPa or more required for the vehicle structural component is ensured, and crashworthiness evaluated by a VDA bending test is improved.

What is claimed is: 
     
         1 . An aluminum alloy sheet for a vehicle structural component, comprising an Al—Mg—Si aluminum alloy sheet that contains, by mass percent, Mg: 0.3 to 1.0%, Si: 0.5 to 1.2%, and Cu: 0.08 to 0.20%, content [Mg] of Mg and content [Si] of Si satisfying a relationship [Si]/[Mg]≧0.7 and a relationship 1.4%≦1.3 [Mg]+[Si]≦1.9%, the remainder consisting of Al and inevitable impurities, and has a thickness of 2.0 mm or more, wherein an average area ratio of cube orientation is 22% or more in a surface region from a surface of the sheet to a depth of 10% in the thickness direction, an yield ratio of the sheet is 0.63 or less, and when the aluminum alloy sheet is stretched by 2% and then subjected to artificial aging for 20 min at 180° C., the aluminum alloy sheet has properties including 0.2% proof stress of 220 MPa or more and crashworthiness showing a bending angle of 60° or more at a VDA bending test. 
     
     
         2 . The aluminum alloy sheet according to  claim 1 , wherein the content [Mg] of Mg and the content [Si] of Si further satisfy a relationship [Si]/[Mg]≧1.8 and a relationship 1.6%≦1.3 [Mg]+[Si]≦1.9%. 
     
     
         3 . The aluminum alloy sheet according to  claim 1 , wherein the aluminum alloy sheet has the average area ratio of cube orientation of 35% or more, and crashworthiness showing the bending angle of 90° or more at the VDA bending test. 
     
     
         4 . The aluminum alloy sheet according to  claim 2 , wherein the aluminum alloy sheet has the average area ratio of cube orientation of 35% or more, and crashworthiness showing the bending angle of 90° or more at the VDA bending test. 
     
     
         5 . A method of manufacturing an aluminum alloy sheet for a vehicle structural component, wherein an Al—Mg—Si aluminum alloy slab containing, by mass percent, Mg: 0.3 to 1.0%, Si: 0.5 to 1.2%, and Cu: 0.08 to 0.20%, content [Mg] of Mg and content [Si] of Si satisfying a relationship [Si]/[Mg]≧0.7 and a relationship 1.4%≦1.3 [Mg]+[Si]≦1.9%, the remainder consisting of Al and inevitable impurities is subjected to homogenization and then rolled into a rolled sheet having a thickness of 2.0 mm or more, the rolled sheet is subjected to solution treatment in which the rolled sheet is held for 0.1 to 30 sec within a range from 540 to 570° C., and is successively subjected to quenching, and is reheated within 10 min after finish of the quenching in such a manner that the rolled sheet is held for 3 to 20 hr within a material temperature range from 60 to 90° C. so as to be formed into an aluminum alloy sheet for a vehicle structural component, and the aluminum alloy sheet has a microstructure and properties, the microstructure including an average area ratio of cube orientation of 22% or more in a surface region from a surface of the sheet to a depth of 10% in the thickness direction, the properties including a yield ratio of 0.63 or less, and including 0.2% proof stress of 220 MPa or more and crashworthiness showing a bending angle of 60° or more at a VDA bending test when the aluminum alloy sheet is stretched by 2% and then subjected to artificial aging for 20 min at 180° C.