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

The patent text discusses the results of a study on improving the mechanical properties of a specific alloy sheet. The researchers found that the average number density of a specific cluster of atoms, which contains Mg or Si atoms, is correlated with the BH responses (a measure of the sheet's formability). Additionally, the distribution state of the size of the aggregates of specific atoms and the average radius of the circle equivalent diameters of these aggregates greatly affect the BH responses. By controlling these factors, the researchers were able to create an alloy sheet that exhibits better BH responses even after long-term room temperature aging.

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 possible without any problem after the lapse of 1 month from the manufacturing, cracking occurred in hem working after the lapse of 3 months.

Moreover, in a case where such room temperature aging is great, a problem also occurs in that the BH responses deteriorate and the proof stress is not improved to the strength required as a panel by heating during an artificial aging (hardening) treatment at a comparatively low temperature, such as a bake treatment and the like of the panel after forming described above.

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