High-strength aluminum alloy plate

Abstract

Provided is an Al—Mg—Si aluminum alloy sheet having a specific chemical composition including a transition element. The microstructure of the sheet includes grains refined to have a smaller average grain size, and includes nanometer-level fine transition-element-dispersed particles. This allows the aluminum alloy sheet to have higher strength during work hardening in forming into a structural component and, synergistically with this, to have better bake hardenability. The resulting aluminum alloy sheet, when formed into an automobile structural component, offers higher strength after bake hardening without deterioration in formability, even after natural aging at room temperature.

1 . A high-strength aluminum alloy sheet being an Al—Mg—Si aluminum alloy sheet comprising, in mass percent:
 Mg in a content of 0.3% to 1.5%; 
 Si in a content of 0.3% to 1.5%; 
 at least one transition element selected from the group consisting of:
 Mn in a content of 0.1% to 0.8%; 
 Zr in a content of 0.04% to 0.20%; 
 Cr in a content of 0.04% to 0.20%; and 
 Sc in a content of 0.02% to 0.1%; and 
 
 Al and unavoidable impurities, 
 wherein, in a microstructure in a thickness central part of the sheet:
 the sheet has an average grain size of 100 μm or less; 
 dispersed particles comprising the at least one transition element have an average equivalent circle diameter of 50 to 300 nm, as measured by TEM-EDX at 50000-fold magnification; and 
 transition-element-dispersed particles each having an equivalent circle diameter of 20 to 400 nm are present in an average number density of 5 or more per cubic micrometer. 
 
 
     
     
         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 greater than 0% to 0.5%; 
 Ag in a content of 0.01% to 0.2%; and 
 Sn in a content of 0.001% to 0.1%.