Aluminum alloy plate having excellent bake hardening responses

Abstract

One of the purposes of the present invention is to provide a 6000-series aluminum alloy plate exhibiting bake hardening (BH) properties and molding properties after aging at room temperature for a long period. In one embodiment of the present invention, in a Sn-containing 6000-series aluminum alloy plate, specific clusters that greatly contribute to the development of the BH properties, which are determined by means of a three-dimensional atom probe field ion microscope, are contained at a predetermined density or more, and the sizes of the atom clusters that meet the aforementioned requirement are uniformed to adjust the average radius of an equivalent circle diameter of each of the clusters to a value falling within a specified range and reduce the standard deviation of the radius of the equivalent circle diameter, whereby the BH properties after aging at room temperature for a long period can be improved.

Description

TECHNICAL FIELD[0001]The present invention relates to an Al—Mg—Si alloy sheet. The aluminum alloy sheet referred to in the present invention means an aluminum alloy sheet that is a rolled sheet such as a hot rolled sheet or a cold rolled sheet and has been subjected to refining such as a solution heat treatment and a quenching treatment, but is not yet subjected to an artificial age hardening treatment such as a bake hardening treatment. Further, aluminum is hereinafter also referred to as Al.BACKGROUND ART[0002]In recent years, because of environmental awareness and the like, the society's requirement for weight reduction in a vehicle such as an automobile has been steadily increasing. In order to respond to such requirement, as a material for a large body panel (an outer panel or an inner panel) of an automobile panel such as a hood, a door, or a roof in particular, instead of a steel material such as a steel sheet, application of an aluminum alloy material excellent in formabilit...

AI Technical Summary

Benefits of technology

[0026]In the first aspect of the present invention, as for the Al—Mg—Si alloy sheet containing Sn, it was found that, among aggregates (clusters) of atoms measured by a 3DAP, the average number density of a specific cluster, which contains Mg atoms or Si atoms by a specific amount or greater in total as the stipulation described above and in which the distance between atoms adjacent to each other which are contained therein is a specific value or less, is greatly correlated with the BH responses.

[0027]Furthermore, according to the present embodiment, it was also found that the distribution state of the size of the aggregates of the specific atoms satisfying these conditions is important, and the average radius of the circle equivalent diameters and the standard deviation of radii of the circle equivalent diameters greatly affect the BH responses.

[0028]That is, in order to improve the BH responses of the Al—Mg—Si alloy sheet containing Sn, it was found to be required that the average radius of the circle equivalent diameters of aggregates of specific atoms is in a specific range of 1.15 nm or greater and 1.45 nm or less and the standard deviation has a small value of 0.45 nm or less for the improvement in BH responses. According to the present aspect, it is possible to provide an Al—Si—Mg alloy sheet which is capable of exhibiting better BH responses even in a case of being subjected to long-term room temperature aging for 100 days.

[0029]In the second aspect of the present invention, as for the Al—Mg—Si alloy sheet containing Sn, it is premised that, among aggregates (clusters) of atoms measured by a 3DAP, a great number of fine clusters in which the distance between the atoms is 0.75 nm or less are present. In addition, the total amount of Mg and Si present in these clusters is balanced with the total amount of Mg...

Problems solved by technology

Here, the 6000 series aluminum alloy had an advantage of having excellent BH responses, but had a problem of aging properties at room temperature, that is, of age hardening during retention at room temperature for several months after the solution heat treatment and quenching treatment to increase the strength, thereby deteriorating formability into a panel, particularly the bendability.

Particularly, in the outer panel subjected to severe bending, there was such a problem that, although forming was po...

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