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.

Description

TECHNICAL FIELD[0001]The present invention relates to Al—Mg—Si aluminum alloy plates or sheets. As used herein, the term “aluminum alloy sheet” refers to a rolled sheet such as a hot-rolled sheet or a cold-rolled sheet, after subjected to heat treatments (temper; T4) such as solution treatment and quenching, but before formed into a structural component to be used. Hereinafter, “aluminum” is also simply referred to as “Al”.BACKGROUND ART[0002]Social demands for weight reduction of vehicles such as automobiles have become higher and higher in consideration typically of global environment. To meet these demands, aluminum alloy materials are increasingly applied as automobile materials instead of ferrous materials such as steel sheets, because the aluminum alloy materials have formability and bake hardening properties (bake hardenability) at excellent levels and have lighter weights. The “bake hardening” is hereinafter also referred to as “BH”.[0003]Representative examples of aluminum ...

AI Technical Summary

Benefits of technology

The present invention is about improving the bake hardenability of a 6xxx-series aluminum alloy sheet. By dispersing nanometer-level fine particles in the microstructure of the sheet, the sheet becomes stronger and easier to shape. The fine particles also contribute to better work hardenability and yield strength, resulting in improved bake hardenability. The fine particles do not negatively affect the formability of the material sheet. This controlled configuration of the 6xxx-series aluminum alloy sheet can be used for automobile structural components requiring higher strength without sacrificing formability.

Problems solved by technology

However, it is not so easy to achieve such higher strength of conventional 6xxx-series aluminum alloy sheets without significantly changing chemical compositions and production conditions of conventional equivalents and without adversely affecting other properties such as formability.