阅读说明：本技术 高强度延性铝合金挤压件 (High strength ductile aluminum alloy extrusion ) 是由 A.T.莫拉莱斯 R.K.米什拉 A.K.萨赫德夫 于 2020-02-07 设计创作，主要内容包括：本发明公开了高强度延性6000系列铝合金挤压件。提供了一种合金组合物。所述合金组合物包含浓度大于或等于约0.55重量%至小于或等于约0.75重量%的硅(Si)；浓度大于或等于约0.55重量%至小于或等于约0.75重量%镁(Mg)；浓度大于或等于约0.15重量%至小于或等于约0.3重量%的铬(Cr)；以及所述合金组合物的余量为铝(Al)。所述合金组合物具有小于或等于约3重量%的金属间相含量。还提供了制备所述合金组合物和加工所述合金组合物的方法。(High strength ductile 6000 series aluminum alloy extrusions are disclosed. An alloy composition is provided. The alloy composition includes silicon (Si) at a concentration of greater than or equal to about 0.55 wt.% to less than or equal to about 0.75 wt.%; magnesium (Mg) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%; chromium (Cr) at a concentration of greater than or equal to about 0.15 wt% to less than or equal to about 0.3 wt%; and the balance of the alloy composition is aluminum (Al). The alloy composition has an intermetallic phase content of less than or equal to about 3 wt%. Methods of making the alloy compositions and processing the alloy compositions are also provided.)

1. An alloy composition comprising:

silicon (Si) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%;

magnesium (Mg) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%;

chromium (Cr) at a concentration of greater than or equal to about 0.15 wt% to less than or equal to about 0.3 wt%; and

the balance of the alloy composition is aluminum (Al),

wherein the alloy composition has an intermetallic phase content of less than or equal to about 3 wt.%.

2. The alloy composition of claim 1, wherein said Si and said Mg are present in a Si to Mg ratio of greater than or equal to about 0.9 (9: 10) to less than or equal to about 1.1 (11: 10).

3. The alloy composition of claim 1, further comprising at least one of:

iron (Fe) at a concentration of greater than or equal to about 0.15 wt.% to less than or equal to about 0.25 wt.%;

copper (Cu) at a concentration greater than about 0 wt% to less than or equal to about 0.3 wt%;

manganese (Mn) at a concentration of greater than or equal to about 0.3 wt% to less than or equal to about 0.5 wt%; and

zinc (Zn) at a concentration of greater than or equal to about 0.1 wt.% to less than or equal to about 0.2 wt.%.

4. The alloy composition of claim 1, wherein the alloy composition is configured to have a bamboo-like grain crystal structure after processing, wherein the bamboo-like grain crystal structure comprises greater than or equal to about 80% directionally aligned longitudinal grains.

5. The alloy composition of claim 1, wherein the alloy composition is configured to have a tensile strength of greater than or equal to about 280MPa after processing.

6. An automotive part comprising the alloy composition of claim 1.

7. A method of manufacturing an extruded object, the method comprising:

heating the alloy composition to a temperature of greater than or equal to about 400 ℃ to less than or equal to about 650 ℃ to form a heated alloy composition;

extruding the heated alloy composition through a die to form a heated extruded part;

quenching the heated extruded part to form a cooled extruded part; and is

Tempering the cooled extruded part to form the extruded object,

wherein the alloy composition comprises:

silicon (Si) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%;

magnesium (Mg) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%;

chromium (Cr) at a concentration of greater than or equal to about 0.15 wt% to less than or equal to about 0.3 wt%; and

the balance of the alloy composition is aluminum (Al),

wherein the alloy composition has an intermetallic phase content of less than or equal to about 3 wt.%.

8. The method of claim 7, wherein the tempering comprises aging the cooled extruded part at a temperature of greater than or equal to about 150 ℃ to less than or equal to about 250 ℃ for a time of greater than or equal to about 1 hour to less than or equal to about 5 hours.

9. The method of claim 7, wherein the extruded object is an automotive part selected from the group consisting of rocker arms, control arms, stringers, cross members, reinforcement plates, bumpers, pedals, sub-frame members, and pillars.

10. The method of claim 7, wherein prior to heating, the alloy composition is subjected to a homogenization process comprising:

heating the alloy composition at a first rate of greater than or equal to about 6 ℃/minute to less than or equal to about 10 ℃/minute until the alloy composition reaches a first temperature of greater than or equal to about 450 ℃ to less than or equal to about 550 ℃;

maintaining the alloy composition at the first temperature for greater than or equal to about 30 minutes to less than or equal to about 2 hours;

heating the alloy composition at a second rate of greater than or equal to about 0.1 ℃/minute to less than or equal to about 1 ℃/minute until the alloy composition reaches a second temperature of greater than or equal to about 550 ℃ to less than or equal to about 600 ℃;

maintaining the alloy composition at the second temperature for greater than or equal to about 1 hour to less than or equal to about 5 hours; and is

Quenching the alloy composition.

Technical Field

The present disclosure relates to high strength ductile 6000 alloy extrusions.

Background

This section provides background information related to the present disclosure that is not necessarily prior art.

Components made from aluminum alloys have become increasingly popular in a variety of industries and applications, including general manufacturing, construction equipment, automotive or other transportation industries, household or industrial structures, aerospace, and the like. For example, aluminum alloys are used in the manufacturing industry for extrusion casting or made from parts having uniform cross-sectional geometries. In particular, 7000-series aluminum alloys (zinc-containing aluminum alloys) have high strength and are lighter in weight than steel, which results in reduced fuel consumption. In contrast, 6000 series aluminum alloys (magnesium and silicon containing aluminum alloys) are easier to machine, but are too weak for many applications using 7000 series alloys. Therefore, it is desirable to develop 6000 series alloys with the strength properties of 7000 series alloys.

Disclosure of Invention

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

The present disclosure relates to high strength ductile 6000 alloy extrusions.

In various aspects, the present techniques provide an alloy composition comprising silicon (Si) in a concentration greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%; magnesium (Mg) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%; chromium (Cr) at a concentration of greater than or equal to about 0.15 wt% to less than or equal to about 0.3 wt%; and the balance of the alloy composition being aluminum (Al), wherein the alloy composition has an intermetallic phase content of less than or equal to about 3 wt.%.

In one aspect, the Si and the Mg are present in a Si: Mg ratio of greater than or equal to about 0.9 (9: 10) to less than or equal to about 1.1 (11: 10).

In one aspect, the alloy composition further comprises at least one of: iron (Fe) at a concentration of greater than or equal to about 0.15 wt.% to less than or equal to about 0.25 wt.%; copper (Cu) at a concentration greater than about 0 wt% to less than or equal to about 0.3 wt%; manganese (Mn) at a concentration of greater than or equal to about 0.3 wt% to less than or equal to about 0.5 wt%; and zinc (Zn) at a concentration of greater than or equal to about 0.1 wt% to less than or equal to about 0.2 wt%.

In one aspect, the alloy composition includes each of Fe, Cu, Mn, and Zn.

In one aspect, the alloy composition is substantially free of titanium (Ti).

In one aspect, the alloy composition is configured to have a bamboo-like grain crystal structure after processing, wherein the bamboo-like grain crystal structure comprises greater than or equal to about 80% directionally aligned longitudinal grains.

In one aspect, the alloy composition is configured to have a tensile strength of greater than or equal to about 280MPa after processing.

In one aspect, the alloy composition is in the form of a billet.

In one aspect, an automotive part comprises the alloy composition.

In various aspects, the present techniques also provide a method of manufacturing an extruded object, the method comprising: heating the alloy composition to a temperature of greater than or equal to about 400 ℃ to less than or equal to about 650 ℃ to form a heated alloy composition; extruding the heated alloy composition through a die to form a heated extruded part; quenching the heated extruded part to form a cooled extruded part; and tempering the cooled extruded part to form an extruded object, wherein the alloy composition comprises silicon (Si) in a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%; magnesium (Mg) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%; chromium (Cr) at a concentration of greater than or equal to about 0.15 wt% to less than or equal to about 0.3 wt%; and the balance of the alloy composition being aluminum (Al), wherein the alloy composition has an intermetallic phase content of less than or equal to about 3 wt.%.

In one aspect, the extrusion is performed with a ram pressure of greater than or equal to about 2500psi to less than or equal to about 5000psi and an extrusion speed of greater than or equal to about 2ipm to less than or equal to about 10 ipm.

In one aspect, quenching is performed by water mist at a cooling rate of greater than or equal to about 300 ℃/minute to less than or equal to about 1200 ℃/min.

In one aspect, tempering comprises aging the cooled extruded part at a temperature of greater than or equal to about 150 ℃ to less than or equal to about 250 ℃ for a time period of greater than or equal to about 1 hour to less than or equal to about 5 hours.

In one aspect, the extruded object has a bamboo-like grain crystal structure comprising greater than or equal to about 80% of the directionally aligned longitudinal grains.

In one aspect, the extruded object is an automotive part selected from the group consisting of a rocker arm, a control arm, a longitudinal beam (rail), a cross beam (beam), a reinforcement panel, a bumper, a step, a secondary frame member, and a pillar (pilar).

In one aspect, prior to heating, subjecting the alloy composition to a homogenization process, which comprises heating the alloy composition at a first rate of greater than or equal to about 6 ℃/minute to less than or equal to about 10 ℃/minute until the alloy composition reaches a first temperature of greater than or equal to about 450 ℃ to less than or equal to about 550 ℃; maintaining the alloy composition at the first temperature for greater than or equal to about 30 minutes to less than or equal to about 2 hours; heating the alloy composition at a second rate of greater than or equal to about 0.1 ℃/minute to less than or equal to about 1 ℃/minute until the alloy composition reaches a second temperature of greater than or equal to about 550 ℃ to less than or equal to about 600 ℃; maintaining the alloy composition at the second temperature for greater than or equal to about 1 hour to less than or equal to about 5 hours; and quenching the alloy composition.

In various aspects, the present techniques still further provide methods of producing an alloy composition, the method comprising combining alloy components to form a mixture, the alloy components comprising silicon (Si) at a concentration of greater than or equal to about 0.55 wt.% to less than or equal to about 0.75 wt.%, magnesium (Mg) at a concentration of greater than or equal to about 0.55 wt.% to less than or equal to about 0.75 wt.%, chromium (Cr) at a concentration of greater than or equal to about 0.15 wt.% to less than or equal to about 0.3 wt.%, and the balance aluminum (Al); melting the mixture to form an alloy solution; casting the alloy solution into a blank; and subjecting the billet to a homogenization process comprising heating the billet at a first rate of greater than or equal to about 6 ℃/minute to less than or equal to about 10 ℃/minute until the billet reaches a first temperature of greater than or equal to about 450 ℃ to less than or equal to about 550 ℃; holding the billet at the first temperature for greater than or equal to about 30 minutes to less than or equal to about 2 hours; heating the blank at a second rate of greater than or equal to about 0.1 ℃/minute to less than or equal to about 1 ℃/minute until the blank reaches a second temperature of greater than or equal to about 550 ℃ to less than or equal to about 600 ℃; holding the billet at the second temperature for greater than or equal to about 1 hour to less than or equal to about 5 hours; and quenching the billet to form the alloy composition.

In one aspect, the Si and the Mg are present in the mixture in a Si to Mg ratio of greater than or equal to about 0.9 (9: 10) to less than or equal to about 1.1 (11: 10).

In one aspect, the alloy composition further comprises at least one of: iron (Fe) at a concentration of greater than or equal to about 0.15 wt.% to less than or equal to about 0.25 wt.%, copper (Cu) at a concentration of greater than about 0 wt.% to less than or equal to about 0.3 wt.%, manganese (Mn) at a concentration of greater than or equal to about 0.3 wt.% to less than or equal to about 0.5 wt.%, and zinc (Zn) at a concentration of greater than or equal to about 0.1 wt.% to less than or equal to about 0.2 wt.%.

In one aspect, the alloy composition has an intermetallic phase content of less than or equal to about 3 wt%.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

Specifically, the present invention discloses the following embodiments:

scheme 1. an alloy composition comprising:

silicon (Si) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%;

magnesium (Mg) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%;

chromium (Cr) at a concentration of greater than or equal to about 0.15 wt% to less than or equal to about 0.3 wt%; and

the balance of the alloy composition is aluminum (Al),

wherein the alloy composition has an intermetallic phase content of less than or equal to about 3 wt.%.

Scheme 2. the alloy composition of scheme 1, wherein the Si and the Mg are present in a Si: Mg ratio of greater than or equal to about 0.9 (9: 10) to less than or equal to about 1.1 (11: 10).

Scheme 3. the alloy composition of scheme 1, further comprising at least one of:

iron (Fe) at a concentration of greater than or equal to about 0.15 wt.% to less than or equal to about 0.25 wt.%;

copper (Cu) at a concentration greater than about 0 wt% to less than or equal to about 0.3 wt%;

manganese (Mn) at a concentration of greater than or equal to about 0.3 wt% to less than or equal to about 0.5 wt%; and

zinc (Zn) at a concentration of greater than or equal to about 0.1 wt.% to less than or equal to about 0.2 wt.%.

Scheme 4. the alloy composition of scheme 3, comprising each of Fe, Cu, Mn, and Zn.

Scheme 5. the alloy composition of scheme 1, wherein the alloy composition is substantially free of titanium (Ti).

Scheme 6. the alloy composition of scheme 1, wherein the alloy composition is configured to have a bamboo-like grain crystal structure after processing, wherein the bamboo-like grain crystal structure comprises greater than or equal to about 80% of directionally aligned longitudinal grains.

Scheme 7. the alloy composition of scheme 1, wherein the alloy composition is configured to have a tensile strength of greater than or equal to about 280MPa after processing.

Scheme 8. the alloy composition of scheme 1, wherein the alloy composition is in the form of a billet.

Scheme 9. an automotive part comprising the alloy composition according to scheme 1.

Scheme 10. a method of manufacturing an extruded object, the method comprising:

heating the alloy composition to a temperature of greater than or equal to about 400 ℃ to less than or equal to about 650 ℃ to form a heated alloy composition;

extruding the heated alloy composition through a die to form a heated extruded part;

quenching the heated extruded part to form a cooled extruded part; and is

Tempering the cooled extruded part to form the extruded object,

wherein the alloy composition comprises:

silicon (Si) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%;

magnesium (Mg) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%;

chromium (Cr) at a concentration of greater than or equal to about 0.15 wt% to less than or equal to about 0.3 wt%; and

the balance of the alloy composition is aluminum (Al),

wherein the alloy composition has an intermetallic phase content of less than or equal to about 3 wt.%.

Scheme 11 the method of scheme 10, wherein the extruding is performed with a ram pressure of greater than or equal to about 2500psi to less than or equal to about 5000psi and an extrusion speed of greater than or equal to about 2ipm to less than or equal to about 10 ipm.

Scheme 12. the method of scheme 10, wherein quenching is performed by water mist at a cooling rate of greater than or equal to about 300 ℃/minute to less than or equal to about 1200 ℃/minute.

Scheme 13. the method of scheme 10, wherein the tempering comprises aging the cooled extruded part at a temperature of greater than or equal to about 150 ℃ to less than or equal to about 250 ℃ for a time of greater than or equal to about 1 hour to less than or equal to about 5 hours.

Scheme 14. the method of scheme 10, wherein the extruded object has a bamboo-like grain crystal structure comprising greater than or equal to about 80% of directionally aligned longitudinal grains.

Scheme 15. the method of scheme 10, wherein the extruded object is an automotive part selected from the group consisting of rocker arms, control arms, stringers, cross members, reinforcement plates, bumpers, pedals, sub-frame members, and pillars.

The method of claim 10, wherein prior to heating, the alloy composition is subjected to a homogenization process comprising:

heating the alloy composition at a first rate of greater than or equal to about 6 ℃/minute to less than or equal to about 10 ℃/minute until the alloy composition reaches a first temperature of greater than or equal to about 450 ℃ to less than or equal to about 550 ℃;

maintaining the alloy composition at the first temperature for greater than or equal to about 30 minutes to less than or equal to about 2 hours;

heating the alloy composition at a second rate of greater than or equal to about 0.1 ℃/minute to less than or equal to about 1 ℃/minute until the alloy composition reaches a second temperature of greater than or equal to about 550 ℃ to less than or equal to about 600 ℃;

maintaining the alloy composition at the second temperature for greater than or equal to about 1 hour to less than or equal to about 5 hours; and is

Quenching the alloy composition.

Scheme 17. a method of producing an alloy composition, the method comprising:

combining alloy components to form a mixture, the alloy components including silicon (Si) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%, magnesium (Mg) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt%, chromium (Cr) at a concentration of greater than or equal to about 0.15 wt% to less than or equal to about 0.3 wt%, and a balance aluminum (Al);

melting the mixture to form an alloy solution;

casting the alloy solution into a billet; and is

Subjecting the blank to a homogenization process comprising:

heating the blank at a first rate of greater than or equal to about 6 ℃/minute to less than or equal to about 10 ℃/minute until the blank reaches a first temperature of greater than or equal to about 450 ℃ to less than or equal to about 550 ℃;

maintaining the billet at the first temperature for greater than or equal to about 30 minutes to less than or equal to about 2 hours;

heating the blank at a second rate of greater than or equal to about 0.1 ℃/minute to less than or equal to about 1 ℃/minute until the blank reaches a second temperature of greater than or equal to about 550 ℃ to less than or equal to about 600 ℃;

maintaining the billet at the second temperature for greater than or equal to about 1 hour to less than or equal to about 5 hours; and is

Quenching the billet to form the alloy composition.

Scheme 18. the method of scheme 17, wherein the Si and the Mg are present in the mixture at a Si to Mg ratio of greater than or equal to about 0.9 (9: 10) to less than or equal to about 1.1 (11: 10).

The method of scheme 19. the method of scheme 17, wherein the alloy composition further comprises at least one of: iron (Fe) at a concentration of greater than or equal to about 0.15 wt.% to less than or equal to about 0.25 wt.%, copper (Cu) at a concentration of greater than about 0 wt.% to less than or equal to about 0.3 wt.%, manganese (Mn) at a concentration of greater than or equal to about 0.3 wt.% to less than or equal to about 0.5 wt.%, and zinc (Zn) at a concentration of greater than or equal to about 0.1 wt.% to less than or equal to about 0.2 wt.%.

Scheme 20. the method of scheme 17, wherein the alloy composition has an intermetallic phase content of less than or equal to about 3 wt.%.

Drawings

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is an electron back-scattered diffraction (EBSD) image showing a microstructure of an alloy composition not in accordance with the present technique. The scale bar is 700 μm.

FIG. 2A is an electron backscatter diffraction (EBSD) image showing a microstructure of an alloy composition in accordance with aspects of the present technique. The scale bar is 700 μm.

FIG. 2B is an enlarged view of a portion of the EBSD image shown in FIG. 2A. The scale bar is 100 μm.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Detailed Description

Exemplary embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those skilled in the art. Numerous specific details are set forth such as examples of specific compositions, components, devices, and methods to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some exemplary embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having" are inclusive and therefore specify the presence of stated features, elements, components, steps, integers, operations, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. While the open-ended term "comprising" is to be understood as a non-limiting term used to describe and claim various embodiments set forth herein, in certain aspects the term is instead understood as a more limiting and restrictive term instead, such as "consisting of … …" or "consisting essentially of … …. Thus, for any given embodiment of any enumerated composition, material, component, element, feature, integer, operation, and/or process step, the present disclosure also specifically includes embodiments that consist of, or consist essentially of, such enumerated composition, material, component, element, feature, integer, operation, and/or process step. In the case of "consisting of … …", alternative embodiments exclude any additional components, materials, components, elements, features, integers, operations, and/or process steps, and in the case of "consisting essentially of … …", exclude from such embodiments any additional components, materials, components, elements, features, integers, operations, and/or process steps that substantially affect the basic and novel characteristics, but may include in embodiments any components, materials, components, elements, features, integers, operations, and/or process steps that do not substantially affect the basic and novel characteristics.

Any method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed unless otherwise indicated.

Although the terms first, second, third, etc. may be used herein to describe various steps, elements, components, regions, layers and/or sections, these steps, elements, components, regions, layers and/or sections should not be limited by these terms unless otherwise specified. These terms may be only used to distinguish one step, element, component, region, layer or section from another step, element, component, region, layer or section. Terms such as "first," "second," and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first step, element, component, region, layer or section discussed below could be termed a second step, element, component, region, layer or section without departing from the teachings of the present exemplary embodiments.

Throughout this disclosure, numerical values represent approximate measurements or limits on the ranges, to encompass minor deviations from the given values and embodiments having values around the stated values as well as those having exactly the stated values. Other than in the working examples provided at the end of the detailed description, all parameter values (e.g., of quantities or conditions) in this specification (including the appended claims) are to be understood as being modified in all instances by the term "about", whether or not "about" actually appears before the value. "about" means that the numerical value allows some slight imprecision (with some approach to exactness in the numerical value; approximately or fairly close to the value; nearly). If the imprecision provided by "about" is not otherwise understood in the art with this ordinary meaning, then "about" as used herein denotes the smallest variable that may result from ordinary methods of measuring and using such parameters. For example, "about" can include variables less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in particular aspects, optionally less than or equal to 0.1%.

Further, the disclosure of a range includes all values within the entire range and further divided ranges, including the endpoints and subranges given for the ranges.

Exemplary embodiments will now be described more fully with reference to the accompanying drawings.

6000 series alloys are cheaper and easier to process than 7000 series alloys. However, the 6000 series is not as strong as the 7000 series alloy. Accordingly, the present technology provides an alloy composition that is a 6000 series alloy, methods of making the alloy composition, and methods of processing the alloy composition.

The present technology provides a method of producing an alloy composition that is a 6000 series alloy. The method includes combining alloy components to form a mixture. The alloy composition includes silicon (Si) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt% or greater than or equal to about 0.6 wt% to less than or equal to about 0.7 wt%, magnesium (Mg) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt% or greater than or equal to about 0.6 wt% to less than or equal to about 0.7 wt%, chromium (Cr) at a concentration of greater than or equal to about 0.1 wt% to less than or equal to about 0.3 wt% or greater than or equal to about 0.2 wt% to less than or equal to about 0.25 wt%, and the balance aluminum (Al).

The Si and the Mg are present in the mixture in substantially equal concentrations. As used herein, a "substantially equal" concentration of Si and Mg means that Si and Mg are present in the mixture at a ratio of Si to Mg of greater than or equal to about 0.9 (9: 10) to less than or equal to about 1.1 (11: 10), greater than or equal to about 0.95 (19: 20) to less than or equal to about 1.05 (21: 20), or greater than or equal to about 0.98 (49: 50) to less than or equal to about 1.02 (51: 50).

In various aspects of the present technique, the alloy composition further includes at least one of: iron (Fe) at a concentration of greater than or equal to about 0.15 wt.% to less than or equal to about 0.25 wt.%, copper (Cu) at a concentration of greater than or equal to about 0 wt.% to less than or equal to about 0.3 wt.%, manganese (Mn) at a concentration of greater than or equal to about 0.3 wt.% to less than or equal to about 0.5 wt.% or greater than or equal to about 0.35 wt.% to less than or equal to about 0.45 wt.%, and zinc (Zn) at a concentration of greater than or equal to about 0.05 wt.% to less than or equal to about 0.15 wt.%. In some aspects of the present technique, the alloy composition further includes each of Fe, Cu, Mn, and Zn.

The alloy composition is substantially free of titanium (Ti). By "substantially free of" Ti, it is meant that the alloy composition contains less than or equal to about 0.1 wt.% Ti or less than or equal to about 0.05 wt.% Ti.

Thus, the alloy composition includes Si, Mg, Cr and Al, and optionally includes at least one of Fe, Cu, Mn and Zn. However, it is to be understood that the alloy composition may include trace levels of contaminants, i.e., other undesirable elements or small molecules. As used herein, "trace levels" include levels greater than or equal to 0 wt% to less than or equal to about 0.1 wt% or greater than 0 wt% to less than or equal to about 0.05 wt% for various undesired contaminants. Thus, in some aspects of the present technique, the alloy composition consists essentially of Si, Mg, Cr, and Al, and at least one of Fe, Cu, Mn, and Zn. Thus, "consisting essentially of … …" means that the alloy composition may also include trace amounts of contaminants. In other aspects of the present technique, the alloy composition consists essentially of Si, Mg, Cr, Fe, Cu, Mn, Zn, and Al. In some embodiments, the alloy composition comprises, consists essentially of, or consists of: greater than or equal to about 0.6 wt% to less than or equal to about 0.7 wt% Si, greater than or equal to about 0.6 wt% to less than or equal to about 0.7 wt% Mg, about 0.2 wt% Fe, less than or equal to about 0.3 wt% Cu, about 0.4 wt% Mn, greater than or equal to about 0.2 wt% to less than or equal to about 0.25 wt% Cr, about 0.1 wt% Zn, and the balance Al.

The method further includes melting the mixture to form an alloy solution and casting the alloy solution into a billet, i.e., a cylindrical shape. Temperatures greater than or equal to about 500 ℃ to less than or equal to about 700 ℃, or greater than or equal to about 560 ℃ to less than or equal to about 660 ℃ are generally suitable for melting. However, it is to be understood that temperatures outside this range may be necessary depending on the elements used. The blank or sheet is then subjected to a two-step homogenization process. The two-step homogenization process comprises the following first step: heating the blank from ambient temperature at a first rate of greater than or equal to about 6 ℃/minute to less than or equal to about 10 ℃/minute until the blank reaches a first temperature of greater than or equal to about 450 ℃ to less than or equal to about 550 ℃ or greater than or equal to about 475 ℃ to less than or equal to about 525 ℃, and holding the blank at the first temperature for greater than or equal to about 30 minutes to less than or equal to about 2 hours or greater than or equal to about 45 minutes to less than or equal to about 1.5 hours. The two-step homogenization process further comprises a second step: heating the blank at a second rate of greater than or equal to about 0.1 ℃/minute to less than or equal to about 1 ℃/minute until the blank reaches a second temperature of greater than or equal to about 550 ℃ to less than or equal to about 600 ℃, and maintaining the blank at the second temperature for greater than or equal to about 1 hour to less than or equal to about 5 hours or greater than or equal to about 2 hours to less than or equal to about 3 hours. Finally, the two-step homogenization process involves quenching (e.g., by forced air cooling) the billet to ambient temperature to form the alloy composition. The quenching is carried out at a rate of greater than or equal to about 1 ℃/sec to less than or equal to about 250 ℃/sec (depending on the quenching medium) in a quenching medium selected from the group consisting of, as non-limiting examples, still water, still oil, molten salt, fluidized bed, flowing air, flowing hot air, still air, and combinations thereof. By way of non-limiting example, a static water quench medium may be used at a rate of about 240 ℃/sec, a static oil quench medium may be used at a rate of about 34 ℃/sec, a molten salt quench medium may be used at a rate of about 19 ℃/sec, a fluidized bed quench medium may be used at a rate of about 9.6 ℃/sec, a flowing air quench medium may be used at a rate of about 40 ℃/sec, a flowing hot air quench medium may be used at a rate of about 3.4 ℃/sec, and a static air quench medium may be used at a rate of about 1.4 ℃/sec.

In an exemplary embodiment, the two-step homogenization comprises: the method includes heating the blank from ambient temperature to a first temperature of about 520 ℃ over a period of about 1 hour, holding the blank or sheet at 520 ℃ for about 1 hour, heating the blank from 520 ℃ to a second temperature of about 585 ℃ at a rate of about 0.5 ℃/minute, holding the blank at 585 ℃ for about 2 hours, and quenching the blank to ambient temperature by forced air cooling to form the alloy composition.

During the two-step homogenization process, large intermetallic particles and inclusions may form after the casting dissolves and produces a saturated solid solution. The precipitation of intermetallic particles and inclusions can be controlled by adjusting the temperature, time and cooling rate employed during the homogenization process. For example, a 6000 series alloy is subjected to a one-step heat treatment comprising heating the 6000 series alloy for 1 hour, heating at a temperature of 560 ℃ to 570 ℃ for 6 hours, and then quenching. When a comparative alloy composition comprising Si, Mg, Fe, Cu, Mn, Zn and Al at the above levels, but no Cr, was subjected to this one-step process, the comparative alloy composition contained about 5 wt% intermetallic phases. In contrast, when the alloy composition of the present technology, which includes not only the same components as the comparative alloy composition, but also Cr, was subjected to a two-step homogenization process, the resulting alloy composition contained only about 1 wt.% intermetallic phases. Thus, the alloy compositions made by the present method have less than or equal to about 3 wt.%, less than or equal to about 2.5 wt.%, less than or equal to about 2 wt.%, or less thanOr equal to about 1.5 weight percent intermetallic phase content. The intermetallic phase depends on the composition of the alloy composition, but in various embodiments, comprises Mg₂Si and α -Al₁₅(FeMn)₃At least one of Si.

The present technology also provides alloy compositions, i.e., 6000 series alloy compositions, which can be produced by the methods described above. The alloy composition includes silicon (Si) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt% or greater than or equal to about 0.6 wt% to less than or equal to about 0.7 wt%, magnesium (Mg) at a concentration of greater than or equal to about 0.55 wt% to less than or equal to about 0.75 wt% or greater than or equal to about 0.6 wt% to less than or equal to about 0.7 wt%, chromium (Cr) at a concentration of greater than or equal to about 0.1 wt% to less than or equal to about 0.3 wt% or greater than or equal to about 0.2 wt% to less than or equal to about 0.25 wt%, and the balance aluminum (Al).

The Si and the Mg are present in the alloy composition in substantially equal concentrations, for example, in a Si to Mg ratio of greater than or equal to about 0.9 (9: 10) to less than or equal to about 1.1 (11: 10), greater than or equal to about 0.95 (19: 20) to less than or equal to about 1.05 (21: 20), or greater than or equal to about 0.98 (49: 50) to less than or equal to about 1.02 (51: 50).

In various aspects of the present technique, the alloy composition further comprises at least one of: iron (Fe) at a concentration of greater than or equal to about 0.10 wt.% to less than or equal to about 0.25 wt.%, copper (Cu) at a concentration of greater than or equal to about 0 wt.% to less than or equal to about 0.3 wt.%, manganese (Mn) at a concentration of greater than or equal to about 0.3 wt.% to less than or equal to about 0.5 wt.% or greater than or equal to about 0.35 wt.% to less than or equal to about 0.45 wt.%, and zinc (Zn) at a concentration of greater than or equal to about 0.05 wt.% to less than or equal to about 0.15 wt.%. In some aspects of the present technique, the alloy composition further comprises each of Fe, Cu, Mn, and Zn.

The alloy composition is substantially free of titanium (Ti). By "substantially free of" Ti, it is meant that the alloy composition comprises less than or equal to about 0.1 wt% Ti or less than or equal to about 0.05 wt% Ti.

Thus, the alloy composition comprises Si, Mg, Cr and Al, and optionally at least one of Fe, Cu, Mn and Zn. However, it is to be understood that the alloy composition may contain trace levels of contaminants, i.e., other undesired elements or small molecules. As used herein, "trace levels" include levels greater than or equal to 0 wt% to less than or equal to about 0.1 wt% or greater than 0 wt% to less than or equal to about 0.05 wt% for various undesired contaminants. Thus, in some aspects of the present technique, the alloy composition consists essentially of Si, Mg, Cr, and Al, and at least one of Fe, Cu, Mn, and Zn. Thus, "consisting essentially of … …" means that the alloy composition may also contain trace amounts of contaminants. In other aspects of the present technique, the alloy composition consists essentially of Si, Mg, Cr, Fe, Cu, Mn, Zn, and Al. In some embodiments, the alloy composition comprises, consists essentially of, or consists of: greater than or equal to about 0.6 wt% to less than or equal to about 0.7 wt% Si, greater than or equal to about 0.6 wt% to less than or equal to about 0.7 wt% Mg, about 0.2 wt% Fe, less than or equal to about 0.3 wt% Cu, about 0.4 wt% Mn, greater than or equal to about 0.2 wt% to less than or equal to about 0.25 wt% Cr, about 0.1 wt% Zn, and the balance Al.

The alloy composition may be in the form of a billet. As a billet, the alloy composition is adapted to undergo an extrusion process that provides a microstructure of the alloy composition that is different from the microstructure of the comparative alloy composition. For example, when the comparative alloy compositions described above were processed according to the method for 6000 series alloys, the microstructure shown in fig. 1 was obtained. Here, Electron Back Scattering Diffraction (EBSD) images show an initial microstructure defined by fibers that are perturbed by grain growth. Thus, the microstructure is spherical, uniform, disordered and random. As a result, the comparative alloy compositions were susceptible to fracture in all directions. In contrast, fig. 2A and 2B show EBSD images of alloy compositions of the present technology after processing, which are described in further detail below. These images show that the processed alloy composition is configured to have a "bamboo-like" fiber microstructure after processing that is not disturbed by grain growth. The bamboo-like grain crystalline structure comprises greater than or equal to about 70%, greater than or equal to about 75%, greater than or equal to about 80%, greater than or equal to about 85%, or greater than or equal to about 90% longitudinal non-spherical grains that are highly uniform, highly ordered, and directionally aligned. Grain size and orientation can be obtained by EBSD. Greater than or equal to about 50%, greater than or equal to about 60%, or greater than or equal to about 70% of the grains have a crystallographic orientation relative to one another of less than or equal to about 15 °, or less than or equal to about 10 °, in the reference (longitudinal) direction. Greater than or equal to about 50%, greater than or equal to about 60%, or greater than or equal to about 70% of the grains have a crystallographic orientation greater than or equal to about 15 °, or greater than or equal to about 20 °, relative to each other and to the reference direction, in a transverse direction relative to the reference direction. The bamboo-like grain crystal structure provides high strength comparable to 7000-series alloys in both the longitudinal (along the grains) and transverse (perpendicular to the grains) directions. Thus, the alloy composition is configured to have a tensile strength of at least about 280MPa, at least about 300MPa, or at least about 350MPa, such as greater than or equal to about 280MPa to less than or equal to about 700MPa or greater.

Alloy compositions having strengths comparable to 7000 series alloys can be processed into extruded objects, such as vehicle parts or other 6000 alloy extrusions. Non-limiting examples of vehicles having parts suitable for production with the alloy composition include automobiles, motorcycles, bicycles, boats, tractors, buses, mobile homes, campers, gliders, airplanes, and military vehicles, such as tanks. In various aspects of the present technique, the extruded object is an automotive part selected from the group consisting of a rocker arm, a control arm, a longitudinal beam, a cross beam, a reinforcement panel, a bumper, a pedal, a secondary frame member, and a pillar. Accordingly, the present technology also provides an automotive part, or other extruded object, comprising the alloy composition.

Thus, the present technology still further provides a method of manufacturing an extruded object by processing the alloy composition. More particularly, the method includes heating the alloy composition to a temperature of greater than or equal to about 400 ℃ to less than or equal to about 650 ℃, greater than or equal to about 450 ℃ to less than or equal to about 600 ℃, or greater than or equal to about 510 ℃ to less than or equal to about 540 ℃ to form a heated alloy composition. Heating may be performed, for example, by heating the alloy composition in the form of a billet in a furnace.

After heating, the method includes extruding the heated alloy composition through a die to form a heated extruded part. The mold includes a slit that matches the cross-sectional geometry of the object being fabricated. The heated extruded part thus has a uniform cross-sectional geometry defined by the die.

The alloy composition is extruded by extruding the alloy composition through a die with an extrusion ram (ram) using a ram pressure of greater than or equal to about 2500psi to less than or equal to about 5000psi, greater than or equal to about 3000psi to less than or equal to about 4500psi, greater than or equal to about 3100psi to less than or equal to about 4200psi, greater than or equal to about 3200psi to less than or equal to about 4000psi, and at an extrusion speed of greater than or equal to about 2 inches per minute (ipm) to less than or equal to about 10ipm, greater than or equal to about 3ipm to less than or equal to about 9ipm, or greater than or equal to about 4ipm to less than or equal to about 8 ipm.

Next, the method includes quenching the heated extruded part to form a cooled extruded part. Quenching is performed at a rate that is fast enough to avoid the formation of undesirable precipitates, but not so fast as to cause cracking or deformation. Thus, quenching includes reducing the temperature of the heated extruded part to ambient temperature at a rate of greater than or equal to about 300 ℃/minute (about 573.15K/minute) to less than or equal to about 1200 ℃/minute (about 1473.15K/minute), greater than or equal to about 400 ℃/minute (about 673.15K/minute) to less than or equal to about 1100 ℃/minute (about 1373.15K/minute), greater than or equal to about 500 ℃/minute (about 773.15K/minute) to less than or equal to about 1000 ℃/minute (about 1273.15K/minute), or greater than or equal to about 526.85 ℃/minute (about 800K/minute) to less than or equal to about 926.85 ℃/minute (about 1200K/minute). Quenching is carried out by any method capable of cooling at the rates described above, such as by contacting the heated extruded part with water or a cold water mist.

The method then includes tempering the cooled extruded part to form an extruded object. Tempering includes aging the cooled extruded object at a temperature of greater than or equal to about 150 ℃ to less than or equal to about 250 ℃, greater than or equal to about 175 ℃ to less than or equal to about 215 ℃, or greater than or equal to about 180 ℃ to less than or equal to about 200 ℃, such as at a temperature of about 150 ℃, about 155 ℃, about 160 ℃, about 165 ℃, about 170 ℃, about 175 ℃, about 180 ℃, about 185 ℃, about 190 ℃, about 195 ℃, about 200 ℃, about 205 ℃, about 210 ℃, about 215 ℃, about 220 ℃, about 225 ℃, about 230 ℃, about 235 ℃, about 240 ℃, about 245 ℃, or about 255 ℃. The aging treatment is carried out for a period of time greater than or equal to about 1 hour to less than or equal to about 5 hours or greater than or equal to about 2 hours to less than or equal to about 4 hours, such as about 1 hour, about 1.5 hours, about 2 hours, about 2.5 hours, about 3 hours, about 3.5 hours, about 4 hours, about 4.5 hours, or about 5 hours.

In various aspects of the present technology, the method further comprises at least one of: drawing the cooled extruded part prior to tempering to improve the flatness of the cooled extruded part; discarding a portion from each end of the cooled extruded part or extruded object before or after tempering because the cooled extruded part or extruded object has a discard length (discard length) of less than or equal to about 5 inches, less than or equal to about 2.5 inches, or less than or equal to about 1 inch, wherever possible; cutting the cooled extruded part or extruded object to a desired size (e.g., it is contemplated that multiple objects may be cut to form a length of extruded object); etching the extruded object; anodizing the extruded object; and further processing the extruded object, for example by bending or debossing into a desired shape.

The extruded object has a bamboo-like grain crystal structure as described above and shown in fig. 2A-2B. In contrast, when the comparative alloy compositions were processed by extrusion at a billet temperature of 482 ℃ to 532 ℃, a stamping pressure of 2400psi to 3100psi, and an extrusion speed of 5ipm to 12ipm, and tempered at 172 ℃ for 10 hours, the microstructures shown in fig. 1 were obtained. Without being bound by theory, it is believed that the Cr and Mn of the present alloy composition precipitate in the form of fine, non-coherent particles of controlled grain size, which enable the retention of fully recrystallized and "bamboo-type" grain structure. By placing the maximum amount of solute in solution, the age hardening capacity is maximized. In addition, some Cr remains in solution and improves the plasticity of the processed alloy composition relative to the processed comparative alloy composition. Thus, the two-step homogenization and tempering process provided by the present technique removes large intermetallic particles that would otherwise be sites of premature fracture initiation and instead places solutes in solution to increase strength.

The foregoing description of the embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. It can also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.