HIGH-STRENGTH CORROSION-RESISTANT 6XXX SERIES ALUMINUM ALLOYS AND METHODS FOR PREPARING THE SAME

CROSS-REFERENCE TO RELATED APPLICATION

[0001]This application claims the benefit of and priority to U.S. Provisional Application No. 63/369,307, filed Jul. 25, 2022, which is incorporated herein by reference in its entirety for all intents and purposes.

FIELD

[0002]The present disclosure relates to the fields of metallurgy, aluminum alloys, aluminum fabrication, and related fields. In particular, the present disclosure generally provides novel 6xxx series aluminum alloys having high corrosion resistance. The disclosure also provides various end uses of such products, such as in automotive, transportation, electronics, industrial, aerospace, and other applications.

BACKGROUND

[0003]High-strength aluminum alloys are used in many different applications, particularly in applications where strength and durability are required. For example, 6xxx series aluminum alloys have been widely used in automobile applications due to their superior combination of properties including strength-to-weight ratio, formability, weldability, and general corrosion resistance. 6xxx series aluminum alloys are commonly used for automotive structural and closure panel applications in place of steel. Because aluminum alloys are generally about 2.8 times less dense than steel, the use of such materials reduces the weight of the vehicle and allows for substantial improvements in fuel economy. Even so, the use of currently available aluminum alloys in automotive applications poses certain challenges.

[0004]Specifically, for 6xxx series aluminum alloys with high copper (Cu) content (e.g., greater than 0.50 wt. % Cu), Cu may segregate at the grain boundary and form a Cu-rich film and precipitate phase particles. For example, Cu in 6xxx series aluminum alloys may form Q-phase precipitate particles (e.g., AlCu₂Mg₈Si₆). Both Q-phase precipitate particles and the Cu-rich film at the grain boundary serve as cathodes as compared to the precipitate-free zone adjacent to the grain boundary, thereby leading to intergranular corrosion (IGC). Therefore, Cu-containing 6xxx series aluminum alloys may be more susceptible to IGC.

SUMMARY

[0005]Covered embodiments of the present disclosure are defined by the claims, not this summary. This summary is a high-level overview of various aspects of the invention and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification, any or all drawings and each claim.

[0006]Described herein are aluminum alloys that include 0.50-2.50 wt. % Si, 0.10-0.50 wt. % Fe, 0.01-1.20 wt. % Cu, 0.01-0.50 wt. % Mn, 0.30-1.50 wt. % Mg, 0.05-0.50 wt % Cr, 0.01-0.50 wt. % Zn, up to 0.20 wt. % Zr, up to 0.15 wt. % of impurities, and Al. In some embodiments, the aluminum alloy comprises 0.60-2.25 wt. % Si, 0.15-0.50 wt. % Fe, 0.01-1.00 wt. % Cu, 0.04-0.45 wt. % Mn, 0.35-1.30 wt. % Mg, 0.10-0.50 wt. % Cr, 0.01-0.40 wt. % Zn, up to 0.20 wt. % Zr, up to 0.15 wt. % of impurities, and Al. In some embodiments, the aluminum alloy comprises 0.70-2.0 wt. % Si, 0.20-0.50 wt. % Fe, 0.05-1.00 wt. % Cu, 0.04-0.40 wt. % Mn, 0.40-1.20 wt. % Mg, 0.10-0.45 wt. % Cr, 0.01-0.30 wt. % Zn, up to 0.15 wt. % Zr, up to 0.15 wt. % of impurities, and Al. In some embodiments, the aluminum alloy comprises 0.80-1.9 wt. % Si, 0.23-0.50 wt. % Fe, 0.20-1.00 wt. % Cu, 0.15-0.40 wt. % Mn, 0.45-1.00 wt. % Mg, 0.15-0.45 wt. % Cr, 0.01-0.20 wt. % Zn, 0.01-0.10 wt. % Zr, up to 0.15 wt. % of impurities, and Al. In some embodiments, the aluminum alloy comprises 1.00-1.70 wt. % Si, 0.30-0.45 wt. % Fe, 0.30-0.80 wt. % Cu, 0.20-0.40 wt. % Mn, 0.50-0.90 wt. % Mg, 0.20-0.40 wt. % Cr, 0.01-0.15 wt. % Zn, 0.05-0.10 wt. % Zr, up to 0.15 wt. % of impurities, and Al. In some embodiments, a ratio of Cr:Cu is at least 0.25:1. In some embodiments, the aluminum alloy comprises 0.20-0.50 wt. % Cu, 0.05 to 0.30 wt. % Cr, and a ratio of Cr:Cu is at least 0.3:1. In some embodiments, the aluminum alloy comprises greater than 0.50 wt. % Cu, 0.20 to 0.50 wt. % Cr, and a ratio of Cr:Cu is at least 0.5:1. In some embodiments, the yield strength of the aluminum alloy is at least 300 MPa when in a T6 temper. In some embodiments, an ultimate tensile strength of the aluminum alloy is at least 350 MPa when in a T6 temper. In some embodiments, the aluminum alloy comprises an inner bend angle less than 140°, when in a T6 temper, as measured according to VDA238-100 (2022). In some embodiments, the aluminum alloy is pre-strained. In some embodiments, the aluminum alloy is subjected to pre-strain treatment and has a maximum corrosion depthless than 300 μm when subjected to an intergranular corrosion (IGC) test set forth in ISO 11846B (2022) for 24 hours. In some embodiments, the aluminum alloy is in a T4 temper. In some embodiments, the aluminum alloy is aged without pre-strain. In some embodiments, the aluminum alloy is artificially aged. In some embodiments, the aluminum alloy has a maximum corrosion depth less than 400 μm when subjected to an intergranular corrosion (IGC) test set forth in ISO 11846B (2022) for 24 hours.

[0007]Described herein are methods of producing an aluminum alloy comprising: casting an aluminum alloy to form a cast product, wherein the aluminum alloy comprises 0.50-2.50 wt. % Si, 0.10-0.50 wt. % Fe, 0.01-1.20 wt. % Cu, 0.01-0.50 wt. % Mn, 0.30-1.50 wt. % Mg, 0.05-0.50 wt. % Cr, 0.01-0.50 wt. % Zn, up to 0.20 wt. % Zr, up to 0.15 wt. % of impurities, and Al; homogenizing the cast product; hot rolling the cast product to produce a hot rolled product; cold rolling the rolled product to produce a final gauge rolled product; and solution heat treating the final gauge rolled product. In some embodiments, the method further comprises aging the final gauge rolled product to a T temper. In some embodiments, the T temper is a T4 temper, a T6 temper, or a T8x temper. In some embodiments, the method further comprises pre-straining the final gauge rolled product. In some embodiments, the method further comprises naturally aging the final gauge rolled product to a T4 temper and artificially aging the final gauge rolled product at a temperature from 150° C. to 200° C. from 10 min to 1 hour, wherein the final gauge rolled product has a maximum corrosion depth less than 300 μm when subjected to an intergranular corrosion (IGC) test set forth in ISO 11846B (2022) for 24 hours.

[0008]Further aspects, objects, and advantages will become apparent upon consideration of the detailed description and figures that follow.

BRIEF DESCRIPTION OF THE FIGURES

[0009]FIG. 1 provides a graph of the average and maximum intergranular corrosion (IGC) depth of example aluminum alloys measured according to ISO 11846B (2022) after immersion for 24 hours according to some embodiments described herein.

[0010]FIG. 2 provides an image of a contour map of the IGC depth in relation to the amount of Cr and Cu in the example aluminum alloys when in a T4 temper and artificially aged at 180° C. for 0.5 hours according to some embodiments described herein.

[0011]FIG. 3 provides an image of a contour map of the IGC depth in relation to the amount of Cr and Cu content in the aluminum alloys when in a T4 temper, subjected to 10% pre-strain, and artificially aged at 180° C. for 1 hour according to some embodiments described herein.

[0012]FIGS. 4A-4D provide scanning transmission electron microscopy (STEM) images of grain boundaries of Example 1 (FIGS. 4A and 4C) and Comparative Example 3 (FIGS. 4B and 4D) according to some embodiments described herein.

[0013]FIGS. 5A-5C provide STEM images of grain boundaries of Example 1 and Comparative Example 3 according to some embodiments described herein.

[0014]FIGS. 6A-6H provides energy dispersive spectrometry (EDS) maps of Example 1 according to some embodiments described herein.

[0015]FIG. 7A-7H provides EDS maps of Comparative Example 3 according to some embodiments described herein.

[0016]FIGS. 8A and 8B provide electron backscatter diffraction (EBSD) grain morphology images of Example 1 and Comparative Example 3 according to some embodiments described herein.

DETAILED DESCRIPTION

[0017]Described herein are novel 6xxx series aluminum alloys which exhibit high corrosion resistance while maintaining high strength-to-weight ratio, formability, and weldability. Among other things, the aluminum alloy described herein includes higher amounts of minor alloying elements (e.g., chromium (Cr) and zirconium (Zr)) to improve the corrosion resistance of products formed from the aluminum alloy without causing a substantial loss in strength. Without being bound to any particular theory, it is believed that including higher amounts of minor alloying elements leads to the formation of a large number of dispersoids during homogenization, which can serve as nucleation sites for precipitates such as Cu-containing precipitate phase particles (e.g., Q-phase precipitates). Because these precipitates form at the location of the dispersoids, they do not form in any substantial degree at grain boundaries of the aluminum alloy. Therefore, the aluminum alloys described herein are significantly less susceptible to intergranular corrosion that conventional 6xxx series aluminum alloys.

[0018]Aluminum alloys exhibit good uniform corrosion resistance due to the presence of a passive film (e.g., a few nanometers thick) naturally formed by oxidation by air. The passive film, however, can be readily broken down at the local sites when exposed to aggressive environments (e.g., chloride-containing electrolytes), resulting in localized corrosion. In particular, Cu-containing 6xxx series aluminum alloys are susceptible to IGC in aggressive environments. For some 6xxx series aluminum alloys, over-aging improves IGC resistance. For example, the maximum depth of IGC may be decreased for some 6xxx series aluminum alloys by prolonging the aging time and pre-strain treatment alone. This process, however, may increase production times and may reduce the overall formability of 6xxx series aluminum alloys.

[0019]The novel 6xxx series aluminum alloys described herein include Cr to improve IGC resistance. Specifically, 6xxx series aluminum alloys that include low amounts of Cu (0.01 to 0.20 wt. %), medium amounts of Cu (e.g., 0.20 to 0.50 wt. %), and high amounts of Cu (greater than 0.50 wt. %) each exhibited significant improvements in IGC resistance when including the Cr content described herein. For example, the maximum depth of IGC for Cu-containing 6xxx series aluminum alloys in corrosive environments was significantly reduced when providing a specific ratio of Cr to Cu as further described below. In fact, 6xxx series aluminum alloys having Cr in amounts from 0.05 wt. % to 0.50 wt. % improved IGC resistance for aluminum alloys having high amounts of Cu, even when compared to 6xxx series aluminum alloys having low amounts of Cu. Additionally, it was found that Cr addition in combination with extended aging and pre-straining synergistically improved IGC resistance for 6xxx series aluminum alloys. The 6xxx series aluminum alloys described herein exhibit reduced segregation at the grain boundary as a result of pre-strain and prolonged aging time, which reduces microgalvanic effects between Cu-rich film at the grain boundary and the precipitate free zone, thus decreasing the aluminum alloy's susceptibility to IGC.

Definitions and Descriptions

[0020]As used herein, the terms “invention,” “the invention,” “this invention” and “the present invention” are intended to refer broadly to all of the subject matter of this patent application and the claims below. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the patent claims below.

[0021]In this description, reference is made to alloys identified by aluminum industry designations, such as “series” or “6xxx.” For an understanding of the number designation system most commonly used in naming and identifying aluminum and its alloys, see “International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys,” or “Registration Record of Aluminum Association Alloy Designations and Chemical Compositions Limits for Aluminum Alloys in the Form of Castings and Ingot,” both published by The Aluminum Association.

[0022]As used herein, the meaning of “a,” “an,” or “the” includes singular and plural references unless the context clearly dictates otherwise.

[0023]As used herein, a plate generally has a thickness of greater than about 15 mm. For example, a plate may refer to an aluminum product having a thickness of greater than about 15 mm, greater than about 20 mm, greater than about 25 mm, greater than about 30 mm, greater than about 35 mm, greater than about 40 mm, greater than about 45 mm, greater than about 50 mm, or greater than about 100 mm.

[0024]As used herein, a shate (also referred to as a sheet plate) generally has a thickness of from about 4 mm to about 15 mm. For example, a shate may have a thickness of about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about 10 mm, about 11 mm, about 12 mm, about 13 mm, about 14 mm, or about 15 mm.

[0025]As used herein, a sheet generally refers to an aluminum product having a thickness of less than about 4 mm (e.g., less than 3 mm, less than 2 mm, less than 1 mm, less than 0.5 mm, less than 0.3 mm, or less than 0.1 mm). For example, a sheet may have a thickness of about 0.1 mm, about 0.2 mm, about 0.3 mm, about 0.4 mm, about 0.5, about 0.6 mm about 0.7 mm, about 0.8 mm, about 0.9 mm, about 1 mm, about 1.1 mm, about 1.2 mm, about 1.3 mm, about 1.4 mm, about 1.5 mm, about 1.6 mm, about 1.7 mm, about 1.8 mm, about 1.9 mm, about 2 mm, about 2.1 mm, about 2.2 mm, about 2.3 mm, about 2.4 mm, about 2.5 mm, about 2.6 mm about 2.7 mm, about 2.8 mm, about 2.9 mm, about 3 mm, about 3.1 mm, about 3.2 mm, about 3.3 mm, about 3.4 mm, about 3.5 mm, about 3.6 mm, about 3.7 mm, about 3.8 mm, about 3.9 mm, or about 4 mm.

[0026]As used herein, formability refers to the ability of a material to undergo deformation into a desired shape without fracturing, tearing-off, necking, earing, or shaping errors such as wrinkling, spring-back, or galling occurring. In engineering, formability may be classified according to deformation modes. Examples of deformation modes include drawing, stretching, bending, and stretch-flanging.

[0027]As used herein, “precipitate phase particles” means the equilibrium phase particles of the meta-stable phase of a 6xxx series aluminum alloy, such as Mg₂Si (beta phase) particles and Al₅Cu₂Mg₈Si₆ (Q phase) particles, among others.

[0028]Reference may be made in this application to alloy temper or condition. For an understanding of the alloy temper descriptions most commonly used, see “American National Standards (ANSI) H35 on Alloy and Temper Designation Systems.” An F condition or temper refers to an aluminum alloy as fabricated. An O condition or temper refers to an aluminum alloy after annealing. An Hxx condition or temper, also referred to herein as an H temper, refers to a non-heat treatable aluminum alloy after cold rolling with or without thermal treatment (e.g., annealing). Suitable H tempers include HX1, HX2, HX3 HX4, HX5, HX6, HX7, HX8, or HX9 tempers. A T1 condition or temper refers to an aluminum alloy cooled from hot working and naturally aged (e.g., at room temperature). A T2 condition or temper refers to an aluminum alloy cooled from hot working, cold worked and naturally aged. A T3 condition or temper refers to an aluminum alloy solution heat treated, cold worked, and naturally aged. A T4 condition or temper refers to an aluminum alloy solution heat treated and naturally aged. A T5 condition or temper refers to an aluminum alloy cooled from hot working and artificially aged (at elevated temperatures). A T6 condition or temper refers to an aluminum alloy solution heat treated and artificially aged. A T7 condition or temper refers to an aluminum alloy solution heat treated and artificially overaged. A T8x condition or temper refers to an aluminum alloy solution heat treated, cold worked, and artificially aged. A T9 condition or temper refers to an aluminum alloy solution heat treated, artificially aged, and cold worked. A W condition or temper refers to an aluminum alloy after solution heat treatment.

[0029]As used herein, the meaning of “room temperature” can include a temperature of from about 15° C. to about 30° C., for example about 15° C., about 16° C., about 17° C., about 18° C., about 19° C., about 20° C., about 21° C., about 22° C., about 23° C., about 24° C., about 25° C., about 26° C., about 27° C., about 28° C., about 29° C., or about 30° C.

[0030]All ranges disclosed herein are to be understood to encompass both endpoints and any and all subranges subsumed therein. For example, a stated range of “1 to 10” should be considered to include any and all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more, e.g., 1 to 6.1, and ending with a maximum value of 10 or less, e.g., 5.5 to 10.

[0031]The following aluminum alloys are described in terms of their elemental composition in weight percentage (wt. %) based on the total weight of the alloy. In certain examples of each alloy, the remainder is aluminum, with a maximum wt. % of 0.15% for the sum of the impurities.

Alloy Compositions

[0032]Aluminum alloy properties are partially determined by the composition of the aluminum alloy. In certain aspects, the alloy composition may influence or even determine whether the alloy will have properties adequate for a desired application.

[0033]Described herein are novel 6xxx series aluminum alloys. The aluminum alloys exhibit high yield strength and bendability, as well as unexpectedly high corrosion resistance at the grain boundaries. The properties of the aluminum alloys are achieved due to the compositions and/or methods of making the alloys.

[0034]In some examples, an aluminum alloy as described herein can have the following elemental composition as provided in Table 1.

[0035]In some examples, the aluminum alloy as described herein can have the following elemental composition as provided in Table 2.

[0036]In some examples, the aluminum alloy as described herein can have the following elemental composition as provided in Table 3.

[0037]In some examples, the aluminum alloy can have the following elemental composition as provided in Table 4.

[0038]In some examples, the aluminum alloy can have the following elemental composition as provided in Table 5.

Silicon (Si)

[0039]In some examples, the aluminum alloy described herein includes Si in an amount of from 0.50% to 2.50% (e.g., from 0.60% to 2.25%, from 0.70% to 2.00%, from 0.80% to 1.90%, or from 1.00 wt. % to 1.70 wt. %) based on the total weight of the alloy. For example, the alloy can include 0.50%, 0.51%, 0.52%, 0.53%, 0.54%, 0.55%, 0.56% 0.57% 0.58%, 0.59%, 0.60%, 0.61%, 0.62%, 0.63%, 0.64%, 0.65%, 0.66%, 0.67%, 0.68%, 0.69%, 0.70%, 0.71%, 0.72%, 0.73%, 0.74%, 0.75, 0.76%, 0.77%, 0.78%, 0.79%, 0.80%, 0.81%, 0.82%, 0.83%, 0.84%, 0.85% 0.86%, 0.87%, 0.88%, 0.89%, 0.90%, 0.91%, 0.92%, 0.93%, 0.94%, 0.95%, 0.96%, 0.97%, 0.98%, 0.99%, 1.00%, 1.01%, 1.02%, 1.03%, 1.04%, 1.05%, 1.06%, 1.07%, 1.08%, 1.09%, 1.10%, 1.11%, 1.12%, 1.13%, 1.14%, 1.15%, 1.16%, 1.17%, 1.18%, 1.19%, 1.2%, 1.21%, 1.22%, 1.23%, 1.24%, 1.25%, 1.26%, 1.27%, 1.28%, 1.29%, 1.3%, 1.31%, 1.32% 1.33%, 1.34%, 1.35%, 1.36%, 1.37%, 1.38%, 1.39%, 1.40%, 1.41%, 1.42% 1.43%, 1.44%, 1.45%, 1.46%, 1.47%, 1.48%, 1.49%, 1.50%, 1.51%, 1.52%, 1.53%, 1.54%, 1.55%, 1.56%, 1.57%, 1.58%, 1.59%, 1.60%, 1.61%, 1.62%, 1.63%, 1.64% 1.65%, 1.66%, 1.67%, 1.68%, 1.69%, 1.70%, 1.71%, 1.72%, 1.73%, 1.74%, 1.75% 1.76%, 1.77%, 1.78%, 1.79%, 1.80%, 1.81%, 1.82%, 1.83%, 1.84%, 1.85%, 1.86%, 1.87%, 1.88%, 1.89%, 1.90%, 1.91%, 1.92%, 1.93%, 1.94%, 1.95%, 1.96%, 1.97%, 1.98%, 1.99%, 2.00%, 2.01%, 2.02%, 2.03%, 2.04%, 2.05%, 2.06%, 2.07%, 2.08%, 2.09%, 2.10%, 2.11%, 2.12%, 2.13%2.14%, 2.15%, 2.16%, 2.17%, 2.18% 2.19%, 2.20%, 2.21%, 2.22%, 2.23%, 2.24%, 2.25%, 2.26%, 2.27%, 2.28%, 2.29%, 2.30%, 2.31%, 2.32%, 2.33%, 2.34%, 2.35%, 2.36%, 2.37%, 2.38%, 2.39%, 2.40%, 2.41%, 2.42%, 2.43%, 2.44%, 2.45%, 2.46%, 2.47%, 2.48%, 2.49%, or 2.50% Si. All expressed in wt.

Iron (Fe)

[0040]In some examples, the aluminum alloy described herein also includes Fe in an amount of from 0.10% to 0.50% (e.g., from 0.15% to 0.50%, from 0.20% to 0.50%, from 0.23% to 0.50%, or from 0.30% to 0.45%) based on the total weight of the alloy. For example, the alloy can include 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.40%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.50% Fe. All expressed in wt. %. Copper (Cu)

[0041]In some examples, the aluminum alloy described herein includes Cu in an amount of from 0.01 to 1.20% (e.g., from 0.01% to 1.00%, 0.05% to 1.00%, 0.20% to 1.00%, or 0.30% to 0.80%) based on the total weight of the alloy. For example, the alloy can include 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28% 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, 0.50%, 0.51%, 0.52%, 0.53%, 0.54%, 0.55%, 0.56%, 0.57%, 0.58%, 0.59%, 0.60%, 0.61%, 0.62%, 0.63%, 0.64%, 0.65%, 0.66%, 0.67%, 0.68%, 0.69%, 0.70%, 0.71%, 0.72%, 0.73%, 0.74%, 0.75%, 0.76%, 0.77%, 0.78%, 0.79%, 0.80%, 0.81%, 0.82%, 0.83% 0.84%, 0.85%, 0.86%, 0.87%, 0.88%, 0.89%, 0.90%, 0.91%, 0.92%, 0.93%, 0.94%, 0.95%, 0.96%, 0.97%, 0.98%, 0.99%, 1.00%, 1.01%, 1.02%, 1.03%, 1.04%, 1.05%, 1.06%, 1.07% 1.08%, 1.09% 1.10%, 1.11%, 1.12%, 1.13%, 1.14%, 1.15%, 1.16%, 1.17%, 1.18%, 1.19%, or 1.20% Cu. All expressed in wt. %.

Manganese (Mn)

[0042]In some examples, the aluminum alloy described herein can include Mn in an amount from 0.01% to 0.50% (e.g., from 0.04% to 0.45%, from 0.04% to 0.40%, from 0.15% to 0.40%, or from 0.20% to 0.40%) based on the total weight of the alloy. For example, the alloy can include 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20% 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.40%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.50% Mn. All expressed in wt. %.

Magnesium (Mg)

[0043]In some examples, the aluminum alloy described herein can include Mg in an amount from 0.30% to 1.50% (e.g., from 0.35% to 1.30%, from 0.40% to 1.20%, from 0.45% to 1.00%, or from 0.50 to 0.90%) based on the total weight of the alloy. For example, the alloy can include 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.40%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, 0.50%, 0.51%, 0.52%, 0.53%, 0.54%, 0.55%, 0.56%, 0.57%, 0.58%, 0.59%, 0.60%, 0.61%, 0.62%, 0.63%, 0.64%, 0.65%, 0.66%, 0.67%, 0.68%, 0.69%, 0.70%, 0.71%, 0.72%, 0.73%, 0.74%, 0.75%, 0.76%, 0.77%, 0.78%, 0.79%, 0.80%, 0.81%, 0.82%, 0.83%, 0.84%, 0.85%, 0.86%, 0.87%, 0.88%, 0.89%, 0.90%, 0.91%, 0.92%, 0.93%, 0.9400, 0.95%, 0.96%, 0.97%, 0.98%, 0.99%, 1.00%, 1.01%, 1.02% 1.03%, 1.04% 1.05%, 1.06%, 1.07%, 1.08%, 1.09%, 1.10%, 1.11%, 1.12%, 1.13%, 1.14% 1.15%, 1.160% 1.17%, 1.18%, 1.19%, 1.20%, 1.21%, 1.22%, 1.23%, 1.24%, 1.25%, 1.26%, 1.27%, 1.28%, 1.29%, 1.30%, 1.31%, 1.32%, 1.33%, 1.34%, 1.35% 1.36%, 1.37% 1.38%, 1.39%, 1.40%, 1.41%, 1.42%, 1.43%, 1.44%, 1.45%, 1.46%, 1.47%, 1.48%, 1.49%, or 1.50% Mg. All expressed in wt. %.

Zinc (Zn)

[0044]In some examples, the aluminum alloy described herein includes Zn in an amount of 0.01% to 0.50% (e.g., from 0.01% to 0.40%, from 0.01% to 0.30%, from 0.01% to 0.20%, or from 0.01% to 0.15%) based on the total weight of the alloy. For example, the alloy can include 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.40%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.50% Zn. In some cases, Zn is not present in the alloy (i.e., 0%). All expressed in wt. %.

Zirconium (Zr)

[0045]In some examples, the aluminum alloy described herein includes Zr in an amount up to 0.20% (e.g., up to 0.15%, up to 0.10%, 0.01% to 0.20%, from 0.01% to 0.15%, from 0.01% to 0.10%, or from 0.05% to 0.10%) based on the total weight of the alloy. For example, the alloy can include 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.20% Zr. In some cases, Zr is not present in the alloy (i.e., 0%). All expressed in wt. %.

Chromium (Cr)

[0046]In some examples, the aluminum alloy described herein includes Cr in an amount of 0.05% to 0.20% (e.g., 0.10% to 0.50%, 0.10% to 0.45%, 0.15% to 0.45%, or 0.20% to 0.40%) based on the total weight of the alloy. For example, the alloy can include 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.160% 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.40%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.50% Cr. All expressed in wt. %.

[0047]In some embodiments, the aluminum alloy comprises a ratio of Cr:Cu that beneficially reduces IGC. In some embodiments, the ratio of Cr:Cu is greater than 0.1:1 (e.g., greater than 0.2:1, greater than 0.25:1, greater than 0.5:1, greater than 0.75:1, greater than 0.8:1, greater than 0.9:1, greater than 1:1, greater than 2:1, greater than 4:1, greater than 5:1, greater than 6:1, greater than 8:1, or greater than 9:1). In some embodiments, the ratio of Cr:Cu ranges from 0.1:1 to 10:1 (e.g., from 0.25:1 to 8:1, from 0.5:1 to 6:1, from 0.8:1 to 5:1, from 1:1 to 5:1, from 1:1 to 4:1, or from 1:1 to 3:1).

[0048]In some embodiments, the amount of Cr added to the 6xxx series aluminum alloy is a function of the Cu content in the aluminum alloy. For example, 0.05 wt. % to 0.20 wt. % Cr may be added to a 6xxx series aluminum alloy that includes 0.01 wt. % to 0.20 wt. % Cu. In some embodiments, 0.05 wt. % to 0.20 wt. % Cr may be added to a 6xxx series aluminum alloy that includes 0.20 wt. % to 0.50 wt. % Cu. In some embodiments, 0.10 wt. % to 0.50 wt. % Cr may be added to a 6xxx series aluminum alloy that includes greater than 0.50 wt. % Cu.

[0049]In some embodiments, a 6xxx series aluminum alloy may include 0.01 to 0.20 wt. % Cu, 0.05 to 0.20 wt. % Cr, and a ratio of Cr:Cu is at least 0.25:1. In some embodiments, a 6xxx series aluminum alloy may include 0.20 to 0.50 wt. % Cu, 0.05 to 0.30 wt. % Cr, and a ratio of Cr:Cu is at least 0.5:1. In some embodiments, a 6xxx series aluminum alloy may include greater than 0.50 wt. % Cu, 0.25 to 0.50 wt. % Cr, and a ratio of Cr:Cu is at least 1:1.

Minor Elements

[0050]Optionally, the aluminum alloys described herein can further include other minor elements, sometimes referred to as impurities, in amounts of 0.05% or below, 0.04% or below, 0.03% or below, 0.02% or below, or 0.01% or below. These impurities may include, but are not limited to Ti, Sc, V, Ni, Hf, Zr, Sn, Ga, Ca, Bi, Na, Pb, or combinations thereof. Accordingly, Ti, Sc, V, Ni, Hf, Zr, Sn, Ga, Ca, Bi, Na, or Pb may be present in alloys in amounts of 0.05% or below, 0.04% or below, 0.03% or below, 0.020% or below, or 0.01% or below. The sum of all impurities does not exceed 0.15% (e.g., 0.1%). All expressed in wt. %. The remaining percentage of each alloy can be aluminum.

Properties

[0051]In some examples, an aluminum alloy product (e.g., an aluminum alloy sheet) produced from the aluminum alloys described herein can have a yield strength of 250 MPa or greater when in a T6 temper. For example, an aluminum alloy product produced from the aluminum alloys described herein can have a yield strength of 260 MPa or greater, 270 MPa or greater, 280 MPa or greater, 290 MPa or greater, 300 MPa or greater, 310 MPa or greater, 320 MPa or greater, 325 MPa or greater, 330 MPa or greater, 335 MPa or greater, 340 MPa or greater, 345 MPa or greater, 350 MPa or greater, 355 MPa or greater, 360 MPa or greater, 365 MPa or greater, or 370 MPa or greater, when in a T6 temper. In some cases, the yield strength is from 250 MPa to 420 MPa (e.g., from 260 MPa to 450 MPa, from 280 MPa to 425 MPa, or from 300 MPa to 400 MPa), or anywhere in between, when in a T6 temper. The aluminum alloy products described herein can exhibit the yield strengths as described herein when measured in a longitudinal (L) direction, a transverse (T) direction, and/or in a diagonal (D) direction, each respective to the rolling direction.

[0052]In some examples, an aluminum alloy product produced from the aluminum alloys described herein can have a yield strength of 200 MPa or greater when in a T8x temper (2% pretrain+185° C. for 20 minutes). For example, an aluminum alloy product produced from the aluminum alloys described herein can have a yield strength of 200 MPa or greater, 210 MPa or greater, 220 MPa or greater, 230 MPa or greater, 240 MPa or greater, 250 MPa or greater, 260 MPa or greater, 270 MPa or greater, 280 MPa or greater, 290 MPa or greater, or 300 MPa or greater, when in a T8x temper. In some cases, the yield strength is from 200 MPa to 350 MPa (e.g., from 210 MPa to 340 MPa, from 220 MPa to 330 MPa, from 230 MPa to 320 MPa, from 240 MPa to 310 MPa, or from 250 MPa to 300 MPa), or anywhere in between, when in a T8x temper. The aluminum alloy products described herein can exhibit the yield strengths as described herein when measured in a longitudinal (L) direction, a transverse (T) direction, and/or in a diagonal (D) direction, each respective to the rolling direction.

[0053]In some examples, an aluminum alloy product produced from the aluminum alloys described herein can have an ultimate tensile strength of about 300 MPa or greater when in a T6 temper. For example, the aluminum alloy products can have an ultimate tensile strength of 310 MPa or greater, 320 MPa or greater, 330 MPa or greater, 340 MPa or greater, 350 MPa or greater, 355 MPa or greater, 360 MPa or greater, 365 MPa or greater, 370 MPa or greater, 375 MPa or greater, 380 MPa or greater, 385 MPa or greater, or 390 MPa or greater when in a T6 temper. In some cases, the ultimate tensile strength is from 300 MPa to 450 MPa (e.g., from 300 MPa to 440 MPa, from 325 MPa to 425 MPa, or from 340 MPa to 400 MPa), or anywhere in between. The aluminum alloy products described herein can exhibit the ultimate tensile strengths as described herein when measured in a longitudinal (L) direction, a transverse (T) direction, and/or in a diagonal (D) direction, each respective to the rolling direction.

[0054]In some examples, an aluminum alloy product produced from the aluminum alloys described herein can have an ultimate tensile strength of about 300 MPa or greater when in a T8x temper. For example, the aluminum alloy products can have an ultimate tensile strength of 310 MPa or greater, 320 MPa or greater, 330 MPa or greater, 340 MPa or greater, 350 MPa or greater, 355 MPa or greater, 360 MPa or greater, 365 MPa or greater, 370 MPa or greater, 375 MPa or greater, 380 MPa or greater, 390 MPa or greater, or 400 MPa or greater, when in a T8x temper. In some cases, the ultimate tensile strength is from 300 MPa to 450 MPa (e.g., from 300 MPa to 440 MPa, from 325 MPa to 425 MPa, or from 340 MPa to 400 MPa), or anywhere in between, when in a T8x temper. The aluminum alloy products described herein can exhibit the ultimate tensile strengths as described herein when measured in a longitudinal (L) direction, a transverse (T) direction, and/or in a diagonal (D) direction, each respective to the rolling direction.

[0055]In some examples, an aluminum alloy product produced from the aluminum alloys described herein can have an inner bend angle from 100° to 140° when in a T6 temper (e.g., from 105° to 140°, from 105° to 135°, from 105° to 130°, or from 110° to 130°) as measured according to VDA238-100 (2022). For example, an aluminum alloy product produced from the aluminum alloys described herein can have an inner bend angle of about 100°, 105°, 110°, 115°, 120°, 125°, 130°, 135°, 140°, 145°, 150°, 155°, or 160°, or anywhere in between, when in a T6 temper, as measured according to VDA238-100 (2022).

[0056]In some examples, an aluminum alloy product produced from the aluminum alloys described herein can have an intergranular corrosion depth of less than 450 microns when measured according to ISO 11846B (2022) for 24 hours, when the aluminum alloy is in a T4 temper (e.g., less than 425 microns, less than 400 microns, less than 375 microns, less than 350 microns, less than 325 microns, less than 300 microns, less than 275 microns, less than 250 microns, less than 225 microns, or less than 200 microns). In some examples, an aluminum alloy product produced from the aluminum alloys described herein can have an intergranular corrosion depth from 150 microns to 450 microns when measured according to ISO 11846B (2022) for 24 hours, when the aluminum alloy is in a T4 temper (e.g., from 175 microns to 425 microns, from 200 microns to 400 microns, from 225 microns to 375 microns, from 250 microns to 375 microns, from 250 microns to 350 microns, or from 260 microns to 340 microns).

[0057]In some examples, an aluminum alloy product produced from the aluminum alloys described herein can have an intergranular corrosion depth of less than 350 microns when measured according to ISO 11846B (2022) for 24 hours, when the aluminum alloy is in a T4 temper and subjected to 10% pre-strain (e.g., less than 340 microns, less than 330 microns, less than 320 microns, less than 310 microns, less than 300 microns, less than 290 microns, less than 280 microns, less than 270 microns, less than 260 microns, or less than 250 microns). In some examples, an aluminum alloy product produced from the aluminum alloys described herein can have an intergranular corrosion depth from 150 microns to 350 microns when measured according to ISO 11846B (2022) for 24 hours, when the aluminum alloy is in a T4 temper and subjected to 10% pre-strain (e.g., from 160 microns to 340 microns, from 170 microns to 330 microns, from 180 microns to 320 microns, from 190 microns to 310 microns, from 200 microns to 300 microns, or from 200 microns to 290 microns).

Methods of Making Aluminum Alloys

[0058]The aluminum alloys described herein can be cast into a cast product using a direct chill (DC) process or can be cast using a continuous casting (CC) process. The casting process is performed according to standards commonly used in the aluminum industry as known to one of skill in the art. The CC process may include, but is not limited to, the use of twin belt casters, twin roll casters, or block casters. In some examples, the casting process is performed by a CC process to form a slab, a strip, or the like. In some examples, the casting process is a DC casting process to form a cast product.

[0059]The cast product, slab, or strip can then be subjected to further processing steps. Optionally, the further processing steps can be used to prepare aluminum alloy products (e.g., sheets, shates, or plates). Such processing steps include, but are not limited to, a homogenization step, a hot rolling step, a cold rolling step, and an optional lacquering step. The processing steps are described below in relation to a cast product. However, the processing steps can also be used for a cast slab or strip, using modifications as known to those of skill in the art.

[0060]In a homogenization step, a cast product may be heated to a homogenization temperature, such as a temperature ranging from 400° C. to 600° C. (e.g., from 410° C. to 590° C., from 420° C. to 580° C., from 430° C. to 560° C., from 450° C. to 550° C., from 460° C. to 550° C., from 480° C. to 550° C., or from 500° C. to 550° C.). For example, the cast product can be heated to a temperature of 400° C., 410° C., 420° C., 430° C., 440° C., 450° C., 460° C., 470° C., 480° C., 490° C., 500° C., 510° C., 520° C., 530° C., 540° C., 550° C., 560° C., 570° C., 580° C., 590° C., or 600° C. In some embodiments, the heating rate to the peak metal temperature can be 70° C./hour or less, 60° C./hour or less, or 50° C./hour or less. The cast product may then be allowed to soak (i.e., held at the indicated temperature) for a period of time to form a homogenized product. In some examples, the total time for the homogenization step, including the heating and soaking phases, can be up to 10 hours.

[0061]In some embodiments, the homogenization step described herein can be a two-stage homogenization. The first stage may include heating a cast product to a first homogenization temperature of 350° C. to 450° C. (e.g., from 360° C. to 440° C., from 370° C. to 430° C., from 380° C. to 420° C., or from 400° C. to 420° C.). For example, the cast product can be heated to a temperature of 350° C., 360° C., 370° C., 380° C., 390° C., 400° C., 410° C., 420° C., 430° C., 440° C., or 450° C. In some cases, the cast product is heated to a first homogenization temperature from 400° C. to 420° C. In some cases, the heating rate to the first homogenization temperature can be 70° C./hour or less, 60° C./hour or less, or 50° C./hour or less. The cast product is then allowed to soak (i.e., held at the indicated temperature first homogenization temperature) for a period of time. In some cases, the cast product is allowed to soak for up to 5 hours (e.g., from 30 minutes to 5 hours, inclusively) at the first homogenization temperature. For example, the cast product can be soaked at a first homogenization temperature from 350° C. to 450° C. for 30 minutes, 1 hour, 2 hours, 3 hours, 4 hours, or 5 hours. In some embodiments, the cast product can be soaked at a first homogenization temperature from 400° C. to 420° C. for 1 hour to 2 hours.

[0062]The second stage may include heating the cast product from the first homogenization temperature to a second homogenization temperature of 450° C. to 550° C. (e.g., from 460° C. to 540° C., from 470° C. to 530° C., from 480° C. to 520° C., or from 480° C. to 510° C.). For example, the cast product can be heated to a temperature of 450° C., 460° C., 470° C., 480° C., 490° C., 500° C., 510° C., 520° C., 530° C., 540° C., or 550° C. In some cases, the cast product is heated to a first homogenization temperature from 480° C. to 510° C. The cast product is then allowed to soak for a period of time at the second homogenization temperature. In some cases, the cast product is allowed to soak for up to 5 hours (e.g., from 30 minutes to 5 hours, inclusively) at the second homogenization temperature. For example, the cast product can be soaked at a second homogenization temperature from 450° C. to 550° C. for 30 minutes, 1 hour, 2 hours, 3 hours, 4 hours, or 5 hours. In some embodiments, the cast product can be soaked at a second homogenization temperature from 480° C. to 510° C. for 0 to 2 hours.

[0063]Following a homogenization step, a hot rolling step can be performed. The homogenized product can be hot rolled using a rolling mill to produce a hot rolled product. Prior to the start of hot rolling, the homogenized product can be allowed to cool to a desired temperature, such as from 200° C. to 425° C. For example, the homogenized product can be allowed to cool to a temperature of from 200° C. to 400° C., 250° C. to 375° C., 300° C. to 425° C., or from 350° C. to 400° C. The homogenized product can then be hot rolled at a hot rolling temperature, for example, from 200° C. to 450° C., to produce a hot rolled product (e.g., a hot rolled plate, a hot rolled shate, or a hot rolled sheet).

[0064]The hot rolled product can be cold rolled using cold rolling mills into thinner products, such as a final gauge rolled product. The final gauge rolled product can have a gauge between 0.5 to 10 mm, e.g., between 0.7 to 6.5 mm. Optionally, the final gauge rolled product can have a gauge of 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm, 4.5 mm, 5.0 mm, 5.5 mm, 6.0 mm, 6.5 mm, 7.0 mm, 7.5 mm, 8.0 mm, 8.5 mm, 9.0 mm, 9.5 mm, or 10.0 mm. The cold rolling can be performed to result in a final gauge thickness that represents a gauge reduction of up to 85% (e.g., up to 10%, up to 20%, up to 30%, up to 40%, up to 50%, up to 60%, up to 70%, up to 80%, or up to 85% reduction) as compared to a gauge prior to the start of cold rolling. In some embodiments, the cold rolling step may include one or more cold rolling steps to achieve the desired gauge thickness reduction. Optionally, the process for producing the aluminum alloy can include an interannealing step (e.g., between one or more cold rolling steps).

[0065]Following hot rolling or cold rolling, the final gauge rolled product can be solution heat treated. The solution heat treatment step may include heating the final gauge rolled product from room temperature to a temperature of from 400° C. to 600° C. (e.g., from 420° C. to 580° C., from 440° C. to 570° C., from 450° C. to 560° C., from 460° C. to 550° C., from 470° C. to 540° C., from 480° C. to 550° C., or from 500° C. to 550° C.). The final gauge rolled product can soak at the temperature for a period of time. In certain aspects, the final gauge rolled product is allowed to soak for up to approximately 2 hours (e.g., from 10 seconds to 120 minutes inclusively). For example, the final gauge rolled product can be soaked at the temperature of from 400° C. to 600° C. for 20 seconds, 25 seconds, 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds, 60 seconds, 65 seconds, 70 seconds, 75 seconds, 80 seconds, 85 seconds, 90 seconds, 95 seconds, 100 seconds, 105 seconds, 110 seconds, 115 seconds, 120 seconds, 125 seconds, 130 seconds, 135 seconds, 140 seconds, 145 seconds, or 150 seconds, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, 65 minutes, 70 minutes, 75 minutes, 80 minutes, 85 minutes, 90 minutes, 95 minutes, 100 minutes, 105 minutes, 110 minutes, 115 minutes, or 120 minutes, or anywhere in between.

[0066]In certain aspects, the heat treatment is performed immediately after the hot or cold rolling step. In certain aspects, the heat treatment is performed after an annealing step. The final gauge rolled product can be naturally aged or artificially aged for a period of time to result in T temper. For example, the final gauge rolled product can be aged to T4 temper, a T6 temper, or a T8x temper (e.g., T81 temper). In some embodiments, the aluminum alloy is aged without pre-strain. In some embodiments, the aluminum alloy is artificially aged. In certain aspects, the final gauge rolled product provided in the T4 temper can be artificially aged (AA) at 160° C. to 250° C. (e.g., 1600 C, 165° C., 1700 C, 175° C., 1800 C, 185° C., 1900 C, 195° C., 200° C., 205° C., 210° C., 215° C., 220° C., 225° C., 230° C., 235° C., 240° C., 245° C., or 250° C.) for a period of time. Optionally, the final gauge rolled product can be artificially aged for a period from 15 minutes to 8 hours (e.g., 15 minutes, 30 minutes, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours or anywhere in between) to result in the T6 temper.

Illustrations of Suitable Methods and Alloy Products

[0067]Illustration 1 is an aluminum alloy comprising 0.50-2.50 wt. % Si, 0.10-0.50 wt. % Fe, 0.01-1.20 wt. % Cu, 0.01-0.50 wt. % Mn, 0.30-1.50 wt. % Mg, 0.05-0.50 wt. % Cr, 0.01-0.50 wt. % Zn, up to 0.20 wt. % Zr, up to 0.15 wt. % of impurities, and Al.

[0068]Illustration 2: The illustration of any preceding or subsequent illustration, wherein the aluminum alloy comprises 0.60-2.25 wt. % Si, 0.15-0.50 wt. % Fe, 0.01-1.00 wt. % Cu, 0.04-0.45 wt. % Mn, 0.35-1.30 wt. % Mg, 0.10-0.50 wt. % Cr, 0.01-0.40 wt. % Zn, up to 0.20 wt. % Zr, up to 0.15 wt. % of impurities, and Al.

[0069]Illustration 3: The illustration of any preceding or subsequent illustration, wherein the aluminum alloy comprises 0.70-2.0 wt. % Si, 0.20-0.50 wt. % Fe, 0.05-1.00 wt. % Cu, 0.04-0.40 wt. % Mn, 0.40-1.20 wt. % Mg, 0.10-0.45 wt. % Cr, 0.01-0.30 wt. % Zn, up to 0.15 wt. % Zr, up to 0.15 wt. % of impurities, and Al.

[0070]Illustration 4: The illustration of any preceding or subsequent illustration, wherein the aluminum alloy comprises 0.80-1.9 wt. % Si, 0.23-0.50 wt. % Fe, 0.20-1.00 wt. % Cu, 0.15-0.40 wt. % Mn, 0.45-1.00 wt. % Mg, 0.15-0.45 wt. % Cr, 0.01-0.20 wt. % Zn, 0.01-0.10 wt. % Zr, up to 0.15 wt. % of impurities, and Al.

[0071]Illustration 5: The illustration of any preceding or subsequent illustration, wherein the aluminum alloy comprises 1.00-1.70 wt. % Si, 0.30-0.45 wt. % Fe, 0.30-0.80 wt. % Cu, 0.20-0.40 wt. % Mn, 0.50-0.90 wt. % Mg, 0.20-0.40 wt. % Cr, 0.01-0.15 wt. % Zn, 0.05-0.10 wt. % Zr, up to 0.15 wt. % of impurities, and Al.

[0072]Illustration 6: The illustration of any preceding or subsequent illustration, wherein a ratio of Cr:Cu is at least 0.25:1.

[0073]Illustration 7: The illustration of any preceding or subsequent illustration, wherein the aluminum alloy comprises 0.20-0.50 wt. % Cu, 0.05 to 0.30 wt. % Cr, and a ratio of Cr:Cu is at least 0.3:1.

[0074]Illustration 8: The illustration of any preceding or subsequent illustration, wherein the aluminum alloy comprises greater than 0.50 wt. % Cu, 0.20 to 0.50 wt. % Cr, and a ratio of Cr:Cu is at least 0.5:1.

[0075]Illustration 9: The illustration of any preceding or subsequent illustration, wherein the yield strength of the aluminum alloy is at least 300 MPa when in a T6 temper.

[0076]Illustration 10: The illustration of any preceding or subsequent illustration, wherein an ultimate tensile strength of the aluminum alloy is at least 350 MPa when in a T6 temper.

[0077]Illustration 11: The illustration of any preceding or subsequent illustration, wherein the aluminum alloy comprises an inner bend angle less than 140°, when in a T6 temper, as measured according to VDA238-100 (2022).

[0078]Illustration 12: The illustration of any preceding or subsequent illustration, wherein the aluminum alloy is pre-strained.

[0079]Illustration 13: The illustration of any preceding or subsequent illustration, wherein the aluminum alloy is subjected to pre-strain treatment and has a maximum corrosion depth less than 300 μm when subjected to an intergranular corrosion (IGC) test set forth in ISO 11846B (2022) for 24 hours.

[0080]Illustration 14: The illustration of any preceding or subsequent illustration, wherein the aluminum alloy is in a T4 temper.

[0081]Illustration 15: The illustration of any preceding or subsequent illustration, wherein the aluminum alloy has a maximum corrosion depth less than 400 μm when subjected to an intergranular corrosion (IGC) test set forth in ISO 11846B (2022) for 24 hours.

[0082]Illustration 16: A method of producing an aluminum alloy comprising: casting an aluminum alloy to form a cast product, wherein the aluminum alloy comprises 0.50-2.50 wt. % Si, 0.10-0.50 wt. % Fe, 0.01-1.20 wt. % Cu, 0.01-0.50 wt. % Mn, 0.30-1.50 wt. % Mg, 0.05-0.50 wt. % Cr, 0.01-0.50 wt. % Zn, up to 0.20 wt. % Zr, up to 0.15 wt. % of impurities, and Al; homogenizing the cast product; hot rolling the cast product to produce a hot rolled product; cold rolling the rolled product to produce a final gauge rolled product; and solution heat treating the final gauge rolled product.

[0083]Illustration 17: The illustration of any preceding or subsequent illustration, further comprising aging the final gauge rolled product to a T temper.

[0084]Illustration 18: The illustration of any preceding or subsequent illustration, wherein the T temper is a T4 temper, a T6 temper, or a T8x temper.

[0085]Illustration 19: The illustration of any preceding or subsequent illustration, further comprising pre-straining the final gauge rolled product.

[0086]Illustration 20: The illustration of any preceding or subsequent illustration, further comprising naturally aging the final gauge rolled product to a T4 temper and artificially aging the final gauge rolled product at a temperature from 150° C. to 200° C. from 10 min to 1 hour, wherein the final gauge rolled product has a maximum corrosion depth less than 300 μm when subjected to an intergranular corrosion (IGC) test set forth in ISO 11846B (2022) for 24 hours.

[0087]The following examples will serve to further illustrate the present invention without, however, constituting any limitation thereof. On the contrary, it is to be clearly understood that resort may be had to various embodiments, modifications, and equivalents thereof which, after reading the description herein, may suggest themselves to those skilled in the art without departing from the spirit of the invention.

Examples

Example 1

[0088]Sample aluminum alloys were tested to determine the properties of the aluminum alloys described herein. Comparative Examples 1-4 and Examples 1-5 were prepared according to the methods described herein. Comparative Examples 1-4 are conventional 6xxx series aluminum alloy compositions, which are currently employed in automobile applications. Examples 1-5 were prepared from the aluminum alloys described herein including Cr from 0.05 to 0.50 wt. %. Table 6 provides the aluminum alloy composition for each of Comparative Examples 1-4 and Examples 1-5.

[0089]As shown in Table 6, Comparative Examples 1-4 are 6xxx series aluminum including 0.54 to 0.91 wt. % Cu. As discussed herein, 6xxx series aluminum alloys including Cu have an increased susceptibility to IGC, especially as the Cu content is higher. Examples 1-5 are 6xxx series aluminum alloys with varied elemental components to evaluate the effect of Cr on alloy compositions with different amounts of Cu. The 6xxx series aluminum alloys aluminum alloy compositions described herein are classified as low amounts of Cu (0.05 to 0.20 wt. %), medium amounts of Cu (e.g., 0.20 to 0.50 wt. %), and high amounts of Cu (greater than 0.50 wt. %).

[0090]FIG. 1 provides a graph of both maximum and average IGC depth (μm) of Comparative Examples 1-4 and Examples 1-5. FIG. 1 provides the maximum and average IGC depth for Comparative Examples 1-4 and Examples 1-5 in a T4 temper and subjected to artificial aging at 180° C. for 0.5 hours and in a T4 temper with 10% pre-strain plus artificial aging at 180° C. for 1 hour, respectively. Examples 1, 3, and 4 exhibited lower maximum and average IGC depth values in comparison to Comparative Examples 1-4. In fact, Example 1, which included 0.27 wt. % Cr, exhibited better IGC resistance than Comparative Examples 1-4. Additionally, Example 1 had less IGC attack than Comparative Examples 3 and 4 despite having a higher amount of Cu. The improved IGC resistance of Example 1 can be attributed to the increased amount of Cr content within the alloy composition. As shown in Table 6, Example 1 comprised 0.64 wt. % of Cu and 0.27 wt. % Cr, Example 2 comprised 0.56 wt. % Cu and 0.02 wt. % Cr, and Comparative Example 4 comprised 0.54 wt. % of Cu and 0.01 wt. % Cr. Comparative Examples 3 and 4 displayed an IGC maximum depth of 430 μm and 375 μm, respectively, while Example 1 with higher Cu and increased Cr content exhibited a maximum IGC depth of 256 μm, when these alloys were provided in a T4 temper and artificially aged at 180° C. for 0.5 hours.

[0091]Additionally, Examples 4 and 5 are examples of low-Cu 6xxx series aluminum alloy compositions with increased amounts of Cr. Specifically, Example 4 includes 0.04 wt. % of Cu and 0.06 wt. % Cr, while Example 5 includes 0.03 wt. % Cu and 0.10 wt. % Cr. The IGC depth values of Examples 4 and 5 were 229 μm and 183 μm, respectively. These findings demonstrate that the addition of Cr to low-Cu containing alloys decreased the overall IGC depth in 6xxx series aluminum alloys. In fact, these findings demonstrate that the addition of Cr to 6xxx series aluminum alloys including a wide range of Cu content can improve the IGC resistance.

[0092]FIG. 2 provides a contour map of the IGC maximum depth for Comparative Examples 1-4 and Examples 1-5, demonstrating the relationship between the amounts of Cr and Cu in the alloy compositions and IGC depth. Comparative Examples 1-4 and Examples 1-5 were provided in a T4 temper and artificially aged at 180° C. for 0.5 hours. Comparative Example 1 exhibited an IGC maximum depth of 328 μm. Comparative Example 3 and Example 2 each comprised a high Cu content of greater than 0.50 wt. %, with Example 2 having the highest Cu content of 0.97 wt. %. Despite having the highest concentration of Cu, Example 2 exhibited a lower maximum IGC depth in comparison to Comparative Example 3. Example 2 had a higher ratio of Cr:Cu (0.13:1) and exhibited better IGC resistance than Comparative Example 3 (0.4:1). The addition of Cr greatly improved the corrosion resistance of Example 2. Examples 1 and 3 also demonstrated less IGC maximum depth (256 and 262 μm, respectively), when compared to Comparative Examples 1-4. Surprisingly, Example 3 included more than double the amount of Cu than Comparative Example 2 (0.26 wt. % and 0.12 wt. %, respectively), however, Example 3 exhibited an IGC maximum depth of 262 μm compared to 281 μm of Comparative Example 2. This may be attributed to the increased Cr content in Example 3 (0.31 wt. % Cr compared to 0.01 wt. % Cr in Comparative Example 2).

[0093]Examples 4 and 5 exhibited lower IGC maximum depths than Examples 1-3 and Comparative Examples 1-4 while having minimal levels of Cu and a slightly increased level of Cr in the alloy composition. Examples 4 and 5 each included a similar amount Cu while Example 5 included a higher Cr content. The higher Cr content in Example 5 contributed to the lower IGC depth. These results indicate that by increasing the Cr content of the aluminum alloy composition relative to the Cu content, the resulting properties are improved over conventional 6xxx series aluminum alloys.

[0094]Comparative Examples 1-4 and Examples 1-5 were evaluated to determine the effect of pre-strain and artificial aging on the IGC depth. The IGC maximum depth is shown in the contour map of FIG. 3. Comparative Examples 1-4 and Examples 1-5 were provided in a T4x temper and then subjected to 10% pre-strain and artificial aging at 180° C. for 1 hour. The maximum IGC depth for Comparative Examples 1-4 and Examples 1-5 shown in FIGS. 2 and 3 are summarized in Table 7 below. As demonstrated in FIG. 3, pre-strain and prolonged aging improved IGC resistance of high Cu-containing alloys (Examples 1-3), however, did not improve IGC resistance of Cu-lean alloys (Examples 4 and 5). Comparative Example 3, which was provided in a T4 temper and artificially aged at 180° C. for 0.5 hours, demonstrated a IGC maximum depth of 430 μm. After 10% pre-strain and artificial aging at 180° C. for 1 hour, Comparative Example 3 exhibited a IGC maximum depth of 285 μm. That is, after pre-strain and an extended time for artificial aging, Comparative Example 3 had reduced IGC attack by 33.7%. Examples 1 and 3 demonstrated an improved IGC resistance compared to both Comparative Examples 1 and 2 after prolonged aging and pre-strain treatment. It was surprisingly found that pre-strain and additional aging in combination with Cr addition synergistically improved IGC resistance. It is contemplated that the prolonged aging and pre-strain may reduce the Cu segregation at the grain boundary which may reduce the microgalvanic effects between Cu-rich film at the grain boundary and the precipitate-free zone, thus decreasing the susceptibility to IGC. These examples demonstrate that Cr addition significantly improves IGC resistance of 6xxx series aluminum alloys with a wide range of Cu content.

[0095]The microstructure of Example 1 and Comparative Example 3 were investigated to determine the effect of Cr addition on the grain boundary microstructure, which is related to IGC resistance. The grain boundary microstructure of Example 1 and Comparative Example 3 were characterized using scanning transmission electron microscopy (STEM). FIGS. 4A-4D provide STEM images of grain boundaries of Example 1 (FIGS. 4A and 4C) and Comparative Example 3 (FIGS. 4B and 4D). Example 1, which included 0.64 wt. % of Cu and 0.27 wt. % Cr, demonstrated a higher number density of dispersoids than Comparative Example 3, which included 0.56 wt. % Cu and 0.02 wt. % Cr, due to the addition of Cr, as shown in FIGS. 4A and 4B. The grain boundary microstructures of Example 1 and Comparative Example 3 were very different. The microstructure of Example 1 included a few elongated precipitates at the grain boundaries with some fine particles at one grain boundary indicated by an arrow in FIG. 4C. In contrast, many fine and elongated precipitates were observed at the grain boundary of Comparative Example 3 as indicated by the arrow in FIG. 4D. The differences at the grain boundary can likely be attributed to the increased Cr content in Example 1 when compared to Comparative Example 3, given that the alloy compositions are relatively the same with the exception of Cr.

[0096]To further investigate the grain boundary microstructure, STEM images of Example 1 (FIG. 5A) and Comparative Example 3 (FIGS. 5B and 5C) were collected. As shown in FIG. 5A, Example 1 included some dispersoids containing Al, Fe, Si, Cr, and Mn in the microstructure (solid arrow) and precipitate phase particles, specifically a few Q-phase precipitates containing Al, Mg, Si, and Cu in the microstructure (dashed arrow, 5A at the grain boundary). For Comparative Example 3, the sample was tilted during STEM imaging so that the electron beam was parallel with the grain boundary plane. FIGS. 5B and 5C show the grain boundary of Comparative Example 3 included a higher number of Q-phase precipitates containing Cu as shown by the dashed arrow in FIG. 5B. The higher Cr content in Example 1 provided a grain boundary having fewer Q phases than Comparative Example 3, thereby decreasing IGC.

[0097]FIG. 6A shows a bright-field STEM image of Example 1 and FIGS. 6B-6H show energy dispersive X-ray spectroscopy (EDS) maps of Al, Mg, Si, Cu, Fe, Cr, and Mn content within the alloy composition, respectively. The microstructure of Example 1 included Q-phase precipitates that contained Si, Al, Mg, and Cu as indicated by arrows in FIGS. 6B-6E. FIG. 7A shows a dark-field STEM image of Comparative Example 3 and FIGS. 7B-7H show EDS maps of Al, Mg, Si, Cu, Fe, Cr, and Mn content within the alloy composition. EDS maps of Comparative Example 3 in FIGS. 7B-7H showing that Q phase precipitates indicated by a solid arrow formed at the grain boundary, while Si and Mg were depleted at the grain boundary between Q phases. However, Cu was present at the grain boundary as shown by a dashed arrow. The Cu-rich film at the grain boundary along with the fine and closely-spaced Q phase precipitates may serve as cathodes that drive IGC, demonstrating Comparative Example 3 had an increased susceptibility to IGC. The Cr at the grain boundary in Example 1 may control the grain size through the formation of the dispersoids and modifies grain boundary microstructure, thereby improving the IGC resistance.

[0098]To better understand the microstructures of Example 1 and Comparative Example 3, electron backscatter diffraction (EBSD) analysis was conducted. FIG. 8 shows that Example 1 and Comparative Example 3 had different microstructures based on the EBSD images. In particular, Example 1 exhibited smaller grains than Comparative Example 3 due to the formation of dispersoids in Example 1. The reduced grain size may affect the diffusion of solutes to the grain boundary, reducing Cu segregation and Q phase formation, and thus resulting in decreased driving force for IGC to occur.

[0099]The yield strength, ultimate tensile strength, and elongation were evaluated for Comparative Examples 1-4 and Examples Alloys 1-5 to understand the effects of Cr on mechanical properties of the 6xxx series aluminum alloys. As shown in Table 8, Comparative Examples 1-4 exhibited different yield strengths due to the different amounts of Mg and Cu in each of the aluminum alloys. Additionally, Comparative Examples 1-4 exhibited a higher yield strength in a T6 temper compared to a T8x temper. For Cu-lean 6xxx series aluminum alloys, such as Example Alloys 4 and 5, the yield strength was not impacted by the addition of Cr.

[0100]Table 8 also includes the tensile strength of the alloy compositions under temper and pre-strain conditions or tempering alone. These results indicate that the increased copper does increase the tensile strength of the alloy. Additionally, the addition of Cr to combat the IGC of the alloy does not decrease the tensile strength of the alloy composition. In parallel, the bending angle was evaluated for the formability of the alloy composition. Comparative Examples 1-4 and Examples 1-5 had comparable bending angles. These results indicate that the aluminum alloys described herein exhibit similar strength and bendability properties. Moreover, the results suggest that the alloy composition can include higher amount of Cr content to reduce IGC while still maintaining comparable physical properties to current 6xxx series aluminum alloys.

[0101]6xxx series aluminum alloys include Cu as a strengthening element to achieve high strength. However, as explained previously, 6xxx series aluminum alloys with high amounts of Cu are more susceptible to IGC. The example alloys described herein demonstrate that Cr may be added to Cu-containing 6xxx series aluminum alloys to improve corrosion resistance. 6xxx series aluminum alloys including the amounts of Cr described herein can improve IGC resistance while maintaining formability, strength and elongation of the alloy.

[0102]All patents, publications, and abstracts cited above are incorporated herein by reference in their entireties. Various embodiments of the invention have been described in fulfillment of the various objectives of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptions thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention as defined in the following claims.