Patent Description:
The present disclosure is directed to aluminum alloy products and the surface features of the same. The disclosure further relates to methods of producing aluminum alloy products.

Aluminum alloy products are often bonded or joined to other metals or alloys, including other aluminum alloys, during fabrication of aluminum alloy and other metals based products. Requirements of the aluminum alloy products include, for example, good bond durability and high resistance to corrosion. Aluminum alloy products can be processed in a manner to enhance the bond durability and corrosion resistance.

In addition, aluminum alloy products should exhibit amenability to resistance spot welding and other joining methods. In addition, the methods should include safeguards such that the replacement of consumable items used in the joining methods is minimized.

Covered embodiments of the invention are defined by the claims, not this summary. The subject matter should be understood by reference to appropriate portions of the entire specification, any or all drawings, and each claim.

The subject matter of the present invention is defined in independent claims <NUM> and <NUM> and in dependent claims <NUM> and <NUM>-<NUM>.

The aluminum alloy product according to the present invention comprises a subsurface portion having a concentration of a migrant element and a bulk portion having a concentration of the migrant element, wherein the subsurface portion extends from the surface to a depth of <NUM> within the interior of the alloy product and wherein the migrant element comprises Mg, Si, Cu, Mn, Cr and/or Fe. In these products, the concentration of the migrant element in the subsurface portion is higher than the concentration of the migrant element in the bulk portion. The aluminum alloy product can optionally comprise a 6xxx series aluminum alloy or a 5xxx series aluminum alloy.

Also described herein is a method of producing an aluminum alloy product as defined in claim <NUM> and claims <NUM>-<NUM> dependent thereon. The method comprises casting an aluminum alloy comprising a migrant element to produce a cast aluminum alloy article, rolling the cast aluminum alloy article to provide a rolled aluminum alloy article, and heat treating the rolled aluminum alloy article to form an aluminum alloy product. The rolling step can be performed at a temperature of from about <NUM> to about <NUM>. The heat treating step can be performed at a temperature of from about <NUM> to about <NUM> and for a duration of about <NUM> seconds or less.

The method can further comprise pretreating the cast aluminum alloy product. The pretreating step can include cleaning a surface of the alloy product, etching the surface of the alloy product, and applying a pretreatment to the surface of the alloy product. Optionally, the pretreating is performed after the heat treating step. The casting can comprise direct chill casting or continuous casting.

Also described herein are aluminum alloy products prepared according to the methods described herein. The aluminum alloy products can comprise motor vehicle body parts, among others.

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

According to the present invention, described herein are metal alloy products, including aluminum alloy products, having desired surface properties. The aluminum alloy products described herein have a concentration of migrant elements, including magnesium and silicon, which can be controlled. In some cases, the concentration of the migrant elements throughout the thickness of the alloy product can be controlled to result in desirable properties. Exemplary desirable properties exhibited by the aluminum alloy products described herein include, for example, high bond durability and high corrosion resistance. The properties of the alloys are achieved due to the methods of processing the alloys to produce the described plates, shates, and sheets. As further described herein, the desirable properties can be achieved by specially designed rolling, heat treating, and/or etching and pretreating techniques.

The terms "invention," "the invention," "this invention" and "the present invention" used herein are intended to refer broadly to all of the subject matter of this patent application and the claims below.

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 "<NPL>" or "<NPL>.

As used herein, the meaning of "a," "an," or "the" includes singular and plural references unless the context clearly dictates otherwise.

As used herein, a plate generally has a thickness of greater than about <NUM>. For example, a plate may refer to an aluminum product having a thickness of greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>.

As used herein, a shate (also referred to as a sheet plate) generally has a thickness of from about <NUM> to about <NUM>. For example, a shate may have a thickness of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>.

As used herein, a sheet generally refers to an aluminum product having a thickness of less than about <NUM>. For example, a sheet may have a thickness of less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>.

Reference is 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. A W condition or temper refers to an aluminum alloy solution heat treated at a temperature greater than a solvus temperature of the aluminum alloy, and quenched. 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.

As used herein, terms such as "cast metal article," "cast article," and the like are interchangeable and refer to a product produced by direct chill casting (including direct chill co-casting) or semi-continuous casting, continuous casting (including, for example, by use of a twin belt caster, a twin roll caster, a block caster, or any other continuous caster), electromagnetic casting, hot top casting, or any other casting method.

As used herein, "bond durability" refers to an ability of a bonding agent bonding two products together to withstand cycled mechanical stress after exposure to environmental conditions that initiate failure of the bonding agent. Bond durability is characterized in terms of number of mechanical stress cycles applied to the bound products, while the bound products are exposed to the environmental conditions, until the bond fails.

As used herein, "room temperature" can include a temperature of from about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>.

All ranges disclosed herein are to be understood to encompass any endpoints and any and all subranges subsumed therein. For example, a stated range of "<NUM> to <NUM>" should be considered to include any and all subranges between (and inclusive of) the minimum value of <NUM> and the maximum value of <NUM>; that is, all subranges beginning with a minimum value of <NUM> or more, e.g. <NUM> to <NUM>, and ending with a maximum value of <NUM> or less, e.g., <NUM> to <NUM>.

Described herein are aluminum alloy products having desired surface properties. Among other properties, the aluminum alloy products described herein contain a controlled concentration of migrant elements throughout the thickness of the alloy product, including within the subsurface of the alloy product. In some non-limiting examples, the disclosed alloy products have improved surface qualities for bonding, joining, friction, corrosion resistance, and optical properties. In certain cases, the alloy products also demonstrate very good anodized qualities. According to the invention, alloys having desirable surface properties, including improved bonding and joining properties, have a low enrichment ratio of magnesium (Mg) and silicon (Si). Differences in the atomic concentration of the migrant elements between the subsurface area and the remainder of the alloy (i.e., the bulk of the alloy product) can cause a gradient in electrochemical activity. The gradient in electrochemical activity can lead to a surface that is more anodically active and prone to being corroded due to galvanic coupling between the subsurface and the bulk portion of the alloy product.

<FIG> is an illustrative representation of an aluminum alloy product <NUM> comprising an aluminum matrix <NUM> that is enriched with Mg <NUM> and Si <NUM>. As shown in <FIG>, Mg <NUM> and Si <NUM> can migrate to an alloy surface during thermal treatments, thus providing undesired surface characteristics. A difference in the atomic concentration of the migrant element between the alloy subsurface and the bulk (remainder) of the alloy can cause a gradient in electrochemical activity as seen in the open circuit potential (OCP) profile <NUM> in <FIG>. <FIG> and <FIG> demonstrate the elemental distribution of Mg and Si, respectively, in 5xxx series (Alloys A and B) and 6xxx series (Alloys C, D, and E) alloy products. The 5xxx series alloys (Alloys A and B) demonstrate less enrichment of Mg and Si near the surface of the alloy product, whereas the 6xxx series alloys (Alloys C, D, and E) demonstrate more enrichment of Mg and Si near the surface as compared to the amount in the remaining portion of the alloy product. Surprisingly, controlling migrant element distribution within the subsurface can reverse the effects shown in <FIG> and provide desirable surface properties, without the need to alter or otherwise adjust the concentration of the elements used to prepare the aluminum alloy product. Such aluminum alloy products containing desirable surface properties, due to a suitable distribution of elements within the subsurface, are described below.

As used herein, the term "subsurface" refers to the portion of the alloy product that extends from the surface to a depth of <NUM> within the interior of the alloy product. The portion of the aluminum alloy product excluding the subsurface portion (e.g., the remainder of the alloy product) is referred to herein as the bulk of the alloy product.

The term "migrant element," as used herein, refers to an element that can diffuse from a first position in the alloy product to a second position in the alloy product, as a result of, for example, one or more of the production and processing steps of the alloy product as further described below. The migrant elements include magnesium (Mg), silicon (Si), copper (Cu), manganese (Mn), chromium (Cr), and iron (Fe). Optionally, the migrant element is in the form of a compound or phase. For example, Mg can be present as Mg<NUM>Si or MgO. Mn and Fe can be present, for example, as Al(FeMn) or Al(Fe,Mn)Si.

In some examples, a migrant element as described herein can diffuse throughout the alloy product such that the concentration of the element is distributed throughout the full thickness of the alloy product (i.e., within the subsurface and the bulk portions). For example, the alloy product can include a concentration of Mg and Si that is distributed throughout the alloy product and not concentrated within the subsurface. Such alloy products display exceptional bond durability and corrosion resistance properties.

According to the invention, a migrant element as described herein can diffuse toward the subsurface portion of the alloy product such that an enrichment of the migrant element is provided near the surface of the alloy product. For example, the alloy product can include a concentration of Cu, Mn, Cr, and/or Fe that is localized within the subsurface portion of the alloy product. Such alloy products display exceptional adhesive performance and can behave as a pretreatment. In addition, alloy products including Cr enrichment within the subsurface can control the Fe-Si particle distribution and thus enhance corrosion resistance.

In either case of a migrant element that is distributed throughout the full thickness of the alloy product or that is localized within the subsurface portion of the alloy product, the migrant element can be homogeneously populated or variably populated within the full thickness or subsurface of the alloy product. As used herein, "homogeneously populated" as related to the migrant elements means that the particular migrant element is evenly distributed within the full thickness or subsurface of the alloy product. In these cases, the concentration of the particular migrant element per region (i.e., within a region of the subsurface or within a region of the full thickness of the alloy product) is relatively constant across regions, on average. As used herein, "relatively constant" as related to migrant element distribution means that the concentration of the element in a first region of the subsurface or full thickness of the alloy product can differ from the concentration of the element in a second region of the subsurface or full thickness of the alloy product up to about <NUM> % (e.g., by up to about <NUM> %, by up to about <NUM> %, by up to about <NUM> %, or by about up to <NUM> %).

In other cases, the concentration of the particular migrant element in a region is variably populated within the full thickness or subsurface of the alloy product. As used herein, "variably populated" as related to migrant element distribution means that the particular migrant element is not evenly distributed within the full thickness or subsurface of the alloy product. For example, a higher concentration of the migrant element can be localized in a first portion of the subsurface (or in a first portion of the full thickness of the alloy product) as compared to the concentration of the same migrant element in a second portion of the subsurface (or in a second portion of the full thickness of the alloy product).

The migrant element distribution within the alloy product is characterized by an enrichment ratio. The enrichment ratio is a comparison of the migrant element concentration in the subsurface to the migrant element concentration in the bulk of the alloy product. In some examples, the enrichment ratio can be calculated by measuring a peak atomic concentration of a migrant element at a depth within the subsurface and at a depth within the thickness of the alloy and outside of the subsurface (i.e., within the bulk of the alloy). The enrichment ratio can be quantified by the following equation: <MAT> For example, the atomic concentration can be measured at <NUM>, which represents a depth within the subsurface of a particular alloy product in which the peak atomic concentration can be found, and at <NUM>, which represents a depth within the bulk portion of a particular alloy product. The enrichment ratio can be provided, for example, using the following equation: <MAT> wherein (atomic concentration)<NUM> represents the concentration of the migrant element at <NUM> and (atomic concentration)<NUM> represents the concentration of the migrant element at <NUM>. The atomic concentrations can be measured using techniques as known to those of ordinary skill in the art, including x-ray photoelectron spectroscopy (XPS).

A low enrichment ratio for a particular element indicates that the concentration of the migrant element is distributed throughout the alloy product and is not localized primarily within the subsurface. Enrichment ratios that are considered as low enrichment ratios include from <NUM> to <NUM>. For example, the enrichment ratio can be <NUM>.

A high enrichment ratio for a particular element indicates that a high concentration of the migrant element is localized within the subsurface of the alloy product. Enrichment ratios that are considered as high enrichment ratios include <NUM> or greater. For example, the enrichment ratio can be approximately <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, or <NUM> or greater.

It is desirable to have an aluminum alloy product having a high enrichment ratio for one or more migrant elements and a low enrichment ratio (e.g., a depletion) for other migrant elements. The aluminum alloy product as described herein has low enrichment ratios for Mg, Si, and/or Cu. The aluminum alloy product as described herein has high enrichment ratios for Cr, Mn, and/or Fe.

In some cases, elemental enrichment in a certain area can be accompanied by an elemental depletion in another area of the aluminum alloy product. In some non-limiting examples, Mg, Si, and/or Cu enrichment can occur in areas of the subsurface of the aluminum alloy product in which Fe and Mn can be depleted. In some other examples, the aluminum alloy product can have a subsurface characterized by Si, Mn, and/or Fe depletion along with Cu enrichment.

In some aspects, migrant element particle size and morphology can affect surface properties of the aluminum alloy product. For example, small Cu dispersoids and/or particles (e.g., less than about <NUM> in diameter) within the subsurface of the aluminum alloy product can provide good bond durability with no significant effect on corrosion susceptibility. Optionally, the Cu dispersoids and/or particles are about <NUM> or less in diameter, about <NUM> or less in diameter, about <NUM> or less in diameter, about <NUM> or less in diameter, about <NUM> or less in diameter, about <NUM> or less in diameter, about <NUM> or less in diameter, about <NUM> or less in diameter, or about <NUM> or less in diameter.

The aluminum alloy products include a 5xxx series aluminum alloy, or a 6xxx series aluminum alloy.

Non-limiting exemplary AA5xxx series alloys for use as the aluminum alloy product can include AA5182, AA5183, AA5005, AA5005A, AA5205, AA5305, AA5505, AA5605, AA5006, AA5106, AA5010, AA5110, AA5110A, AA5210, AA5310, AA5016, AA5017, AA5018, AA5018A, AA5019, AA5019A, AA5119, AA5119A, AA5021, AA5022, AA5023, AA5024, AA5026, AA5027, AA5028, AA5040, AA5140, AA5041, AA5042, AA5043, AA5049, AA5149, AA5249, AA5349, AA5449, AA5449A, AA5050, AA5050A, AA5050C, AA5150, AA5051, AA5051A, AA5151, AA5251, AA5251A, AA5351, AA5451, AA5052, AA5252, AA5352, AA5154, AA5154A, AA5154B, AA5154C, AA5254, AA5354, AA5454, AA5554, AA5654, AA5654A, AA5754, AA5854, AA5954, AA5056, AA5356, AA5356A, AA5456, AA5456A, AA5456B, AA5556, AA5556A, AA5556B, AA5556C, AA5257, AA5457, AA5557, AA5657, AA5058, AA5059, AA5070, AA5180, AA5180A, AA5082, AA5182, AA5083, AA5183, AA5183A, AA5283, AA5283A, AA5283B, AA5383, AA5483, AA5086, AA5186, AA5087, AA5187, and AA5088.

Non-limiting exemplary AA6xxx series alloys for use as the aluminum alloy product can include AA6101, AA6101A, AA6101B, AA6201, AA6201A, AA6401, AA6501, AA6002, AA6003, AA6103, AA6005, AA6005A, AA6005B, AA6005C, AA6105, AA6205, AA6305, AA6006, AA6106, AA6206, AA6306, AA6008, AA6009, AA6010, AA6110, AA6110A, AA6011, AA6111, AA6012, AA6012A, AA6013, AA6113, AA6014, AA6015, AA6016, AA6016A, AA6116, AA6018, AA6019, AA6020, AA6021, AA6022, AA6023, AA6024, AA6025, AA6026, AA6027, AA6028, AA6031, AA6032, AA6033, AA6040, AA6041, AA6042, AA6043, AA6151, AA6351, AA6351A, AA6451, AA6951, AA6053, AA6055, AA6056, AA6156, AA6060, AA6160, AA6260, AA6360, AA6460, AA6460B, AA6560, AA6660, AA6061, AA6061A, AA6261, AA6361, AA6162, AA6262, AA6262A, AA6063, AA6063A, AA6463, AA6463A, AA6763, A6963, AA6064, AA6064A, AA6065, AA6066, AA6068, AA6069, AA6070, AA6081, AA6181, AA6181A, AA6082, AA6082A, AA6182, AA6091, and AA6092.

The aluminum alloy product can have any suitable gauge. For example, the aluminum alloy product can be an aluminum alloy plate, an aluminum alloy shate, or an aluminum alloy sheet having a gauge between about <NUM> and about <NUM> (e.g., about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or anywhere in between).

In certain aspects, the disclosed alloy products can be prepared using a method as described herein. Without intending to limit the invention, aluminum alloy properties are partially determined by the formation of microstructures during the preparation of the alloy. In certain aspects, the method of preparation for an alloy composition determines whether the alloy will have properties adequate for a desired application. As described below, certain processing steps and conditions, including the rolling (e.g., hot rolling and/or cold rolling), heat treating (e.g., homogenizing, solutionizing, and/or annealing), and pretreatment steps and conditions, provide the alloy products described above having the desirable bond durability and corrosion resistance properties. The methods of producing aluminum alloy products as described herein include the steps of casting a molten aluminum alloy to form a cast aluminum alloy article, and processing the aluminum alloy article by one or more steps, including quenching, rolling, heat treating, and/or pretreating to form an aluminum alloy product.

In some cases, the aluminum alloy products described herein can be cast using a direct chill (DC) casting process to form a cast product such as an ingot. The resulting ingots can then be scalped. The cast product can then be subjected to further processing steps. In one non-limiting example, the processing method includes homogenizing the aluminum alloy ingot and hot rolling the aluminum alloy ingot to form an aluminum alloy hot band. The aluminum alloy hot band can then be subjected to cold rolling, solution heat treatment, and optionally a pretreatment step.

The homogenization step can include heating a cast product prepared from an alloy composition as described herein to attain a peak metal temperature (PMT) of about, or at least about, <NUM> (e.g., at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM>). For example, the ingot can be heated to a temperature of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>. In some cases, the heating rate to the PMT can be about <NUM>/hour or less, about <NUM>/hour or less, about <NUM>/hour or less, about <NUM>/hour or less, about <NUM>/hour or less, about <NUM>/hour or less, about <NUM>/hour or less, or about <NUM>/hour or less. In other cases, the heating rate to the PMT can be from about <NUM>/min to about <NUM>/min (e.g., about <NUM>/min to about <NUM>/min, about <NUM>/min to about <NUM>/min, about <NUM>/min to about <NUM>/min, from about <NUM>/min to about <NUM>/min, from about <NUM>/min to about <NUM>/min, from about <NUM>/min to about <NUM>/min, or from about <NUM>/min to about <NUM>/min).

The ingot is then allowed to soak (i.e., held at the indicated temperature) for a period of time. According to one non-limiting example, the ingot is allowed to soak for up to about <NUM> hours (e.g., from about <NUM> minutes to about <NUM> hours, inclusively). For example, the ingot can be soaked at a temperature of at least about <NUM> for about <NUM> minutes, about <NUM> hour, about <NUM> hours, about <NUM> hours, about <NUM> hours, about <NUM> hours, or about <NUM> hours, or anywhere in between.

Following the homogenization step, a hot rolling step can be performed to form a hot band. In certain cases, the ingots are laid down and hot-rolled. The hot rolling temperature can be from about <NUM> to about <NUM> (e.g., from about <NUM> to about <NUM>, from about <NUM> to about <NUM>). For example, the hot rolling temperature can be about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>.

In some non-limiting examples, a hot roll exit temperature can be from about <NUM> to about <NUM>. In some examples, the hot roll exit temperature should not exceed about <NUM>. For example, the hot roll exit temperature can range from about <NUM> to about <NUM> (e.g., from about <NUM> to about <NUM>). In these examples, the hot roll exit temperature can be about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>.

In certain cases, the cast article can be hot rolled to an about <NUM> to about <NUM> thick gauge (e.g., from about <NUM> to about <NUM> thick gauge), which is referred to as a shate. For example, the ingot can be hot rolled to an about <NUM> thick gauge, about <NUM> thick gauge, about <NUM> thick gauge, about <NUM> thick gauge, about <NUM> thick gauge, about <NUM> thick gauge, about <NUM> thick gauge, about <NUM> thick gauge, about <NUM> thick gauge, about <NUM> thick gauge, about <NUM> thick gauge, or about <NUM> thick gauge. In certain cases, the ingot can be hot rolled to a gauge greater than <NUM> thick (i.e., a plate). In other cases, the ingot can be hot rolled to a gauge less than <NUM> (i.e., a sheet).

A cold rolling step can be performed following the hot rolling step. In certain aspects, the hot band from the hot rolling step can be cold rolled to a sheet. The hot band temperature can be reduced to a temperature ranging from about <NUM> to about <NUM> (e.g., from about <NUM> to about <NUM>). The cold rolling step can be performed for a period of time to result in a desired final gauge thickness. Optionally, the cold rolling step can be performed for a period of up to about <NUM> hour (e.g., from about <NUM> minutes to about <NUM> minutes). For example, the cold rolling step can be performed for a period of about <NUM> minutes, about <NUM> minutes, about <NUM> minutes, about <NUM> minutes, about <NUM> minutes, or about <NUM> hour.

Optionally, the desired final gauge thickness is below approximately <NUM>. In certain aspects, the rolled product is cold rolled to a thickness of about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to less than about <NUM>. In certain aspects, the alloy is cold rolled to about <NUM> or less, about <NUM> or less, about <NUM> or less, about <NUM> or less, about <NUM> or less, about <NUM> or less, about <NUM> or less, about <NUM> or less, about <NUM> or less, about <NUM> or less, or about <NUM> or less, or anywhere in between.

The cold rolled coil can then be solutionized in a solution heat treatment step. The solutionizing can include heating the final gauge aluminum alloy from room temperature to a temperature of from about <NUM> to about <NUM> (e.g., from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>). For example, the solutionizing step can be performed by heating the final gauge aluminum alloy to about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>.

In some examples, the solutionizing is performed at a temperature of <NUM> or below (e.g., from about <NUM> to about <NUM>). For example, the solutionizing can be performed at a temperature of about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. Solutionizing at a temperature of <NUM> or below can result in an alloy product having a desired particle size and particle size distribution of migrant element particles within the alloy product subsurface and the alloy product bulk, and having a low enrichment ratio for certain migrant elements (e.g., Mg and Si).

The cold rolled coil can soak at the solutionizing temperature for a period of time. In certain aspects, the cold rolled coil is allowed to soak for up to approximately <NUM> hours (e.g., from about <NUM> second to about <NUM> minutes, inclusively). For example, the cold rolled coil can be soaked at the solutionizing temperature of from about <NUM> to about <NUM> for <NUM> second, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> seconds, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, or <NUM> minutes, or anywhere in between.

In some examples, a shorter soaking duration is desirable. For example, the cold rolled coil can be allowed to soak for about <NUM> seconds or less (e.g., <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, <NUM> seconds or less, or <NUM> second).

In certain aspects, the aluminum alloy product can then be cooled to a temperature of about <NUM> at a quench speed that can vary between about <NUM>/s to <NUM>/s in a quenching step that is based on the selected gauge. For example, the quench rate can be from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, or from about <NUM>/s to about <NUM>/s.

In the quenching step, the aluminum alloy product is quenched with a liquid (e.g., water) and/or gas or another selected quench medium. In certain aspects, the aluminum alloy product can be air quenched. The aluminum alloy product can optionally undergo a pretreatment process, as further described below.

The aluminum alloy products described herein can be cast using a continuous casting (CC) process to form a cast aluminum alloy article. 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 cast product such as a billet, slab, shate, strip, or the like. The CC method described herein can include extracting heat from the molten alloy by cooling the molten alloy with water, controlling a feed rate of the molten alloy, or controlling a casting speed of the molten alloy, as further described below. Extracting heat from the molten alloy can control diffusion of migrant elements within the molten alloy.

In some non-limiting examples, the continuous casting method can include extracting heat in a controlled manner to control diffusion of migrant elements within the metal article. In some aspects, solidifying a molten alloy without controlled heat extraction can allow undesired diffusion of the migrant elements within the molten alloy. In some cases, the migrant elements can diffuse to a surface of the molten alloy during solidifying, providing a cast metal article having undesired surface properties. In some non-limiting examples, controlling a rate of solidification (e.g., extracting heat in a controlled manner) can control diffusion of the migrant elements, thus providing a cast metal article with desired surface properties. Controlling the diffusion of the migrant elements can provide selective enrichment of a cast metal article surface, thus providing a cast metal article having tailored surface properties.

Extracting heat from the molten alloy can be performed by any suitable method, including cooling with water, cooling with air, controlling a feed rate of the molten alloy into the casting cavity, or controlling a speed of a pair of moving opposed casting surfaces. Cooling with water can be performed by employing either one or a plurality of nozzles to deliver water directly onto the molten alloy. Likewise, cooling with air can be performed by employing either one or a plurality of nozzles to deliver forced air directly onto the molten alloy. In some examples, controlling the feed rate of the molten alloy into the casting cavity can control the diffusion of the migrant elements. A slower feed rate can allow the molten alloy to solidify closer to the molten metal injector, thus suppressing any undesired diffusion of the migrant elements. Likewise, a faster feed rate can allow the molten alloy to solidify farther from the molten metal injector, thus allowing undesired diffusion of the migrant elements. In some examples, controlling the speed of the pair of moving opposed casting surfaces can control the diffusion of the migrant elements. A slower speed of the pair of moving opposed casting surfaces can allow the molten alloy to solidify closer to the molten metal injector, thus suppressing any undesired diffusion of the migrant elements. Likewise, a faster speed of the pair of moving opposed casting surfaces can allow the molten alloy to solidify farther from the molten metal injector, thus allowing undesired diffusion of the migrant elements.

In some non-limiting examples, controlling the diffusion rate of the migrant elements can provide selective diffusion of the migrant elements. For example, heat can be extracted from the molten metal at a rate that can promote diffusion of a first migrant element and simultaneously suppress diffusion of a second migrant element. Thus, the metal article surface can be selectively enriched by a select migrant element during solidification of the molten alloy to provide the metal article.

The cast aluminum alloy article is then subjected to further processing steps to form the aluminum alloy product. The processing steps include, for example, quenching, hot rolling, cold rolling, and/or annealing steps.

After the casting step, the cast aluminum alloy article can be quenched. In the quenching step, the cast aluminum alloy article can be cooled to a temperature at or below about <NUM>. For example, the cast aluminum alloy article can be cooled to a temperature at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, at or below about <NUM>, or at or below about <NUM> (e.g., about <NUM>). The quenching step can be performed using a liquid (e.g., water), a gas (e.g., air), or another selected quench medium.

The method also includes a step of hot rolling the cast aluminum alloy article to produce a rolled aluminum alloy article (e.g., a hot band). The step of hot rolling the cast aluminum alloy article can include reducing the thickness of the cast aluminum alloy article by at least about <NUM> % and up to about <NUM>% (e.g., by about <NUM>%, by about <NUM> %, by about <NUM> %, by about <NUM> %, by about <NUM> %, by about <NUM> %, by about <NUM> %, by about <NUM> %, by about <NUM> %, or by about <NUM> %). Hot rolling can be performed at a temperature of from about <NUM> to about <NUM> (e.g., from about <NUM> to about <NUM> or from about <NUM> to about <NUM>). For example, the hot rolling step can be performed at a temperature of about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or anywhere in between.

A cold rolling step can then be performed using, for example, a single stand mill or a multi-stand mill. In some cases, the cold rolling step is a one-stage cold rolling process. In some cases, the cold rolling step is a two-stage cold rolling process.

In the one-stage cold rolling process, the coil or sheet temperature can be reduced to a temperature ranging from about <NUM> to about <NUM> (e.g., from about <NUM> to about <NUM>). In some cases, the coil or sheet is cold rolled with an entry temperature range of from about <NUM> to about <NUM>. The entry temperature can be, for example, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some cases, the cold roll exit temperature can range from about <NUM> to about <NUM>. The cold roll exit temperature can be, for example, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>.

The cold rolling step can be performed for a period of time to result in a gauge of from about <NUM> to about <NUM>. For example, the resulting gauge can be from about <NUM> to about <NUM> or from about <NUM> to about <NUM>. Optionally, the cold rolling step can be performed for a period of up to about <NUM> hour (e.g., from about <NUM> minutes to about <NUM> minutes). For example, the cold rolling step can be performed for a period of about <NUM> minutes, about <NUM> minutes, about <NUM> minutes, about <NUM> minutes, about <NUM> minutes, or about <NUM> hour.

As discussed above, the cold rolling step can be a two-stage cold rolling process in which an intervening annealing step is performed during the cold rolling. In the two-stage cold rolling process, the coil or sheet temperature can be reduced to a temperature ranging from about <NUM> to about <NUM> (e.g., from about <NUM> to about <NUM>). In some cases, the coil or sheet is cold rolled with an entry temperature range of from about <NUM> to about <NUM>. The entry temperature can be, for example, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some cases, the cold roll exit temperature can range from about <NUM> to about <NUM>. The exit temperature can be, for example, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>.

The first stage of the cold rolling step can be performed for a period of time to result in a gauge of from about <NUM> to about <NUM>. For example, the resulting gauge can be from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>. Optionally, the cold rolling step can be performed for a period of up to about <NUM> hour (e.g., from about <NUM> minutes to about <NUM> minutes). For example, the cold rolling step can be performed for a period of about <NUM> minutes, about <NUM> minutes, about <NUM> minutes, about <NUM> minutes, about <NUM> minutes, or about <NUM> hour.

As the next step of the two-stage cold rolling process, an annealing process referred to herein as an intermediate annealing step can be performed. In the intermediate annealing step, the cold rolled gauge can be held at a temperature ranging from about <NUM> to about <NUM> (e.g., from about <NUM> to about <NUM> or from about <NUM> to about <NUM>), with a soak time of up to about <NUM> hours. For example, the soak time can range from about <NUM> minutes to about <NUM> hours (e.g., about <NUM> minutes, about <NUM> minutes, about <NUM> hour, about <NUM> hours, about <NUM> hours, or about <NUM> hours). Optionally, the intermediate annealing step can result in an alloy having grains that are round.

Following the intermediate annealing step, a second stage of the cold-rolling process can be performed. In some cases, the second stage of the cold-rolling process includes cold rolling using a single stand mill or a multi-stand mill with an entry temperature range of from about <NUM> to about <NUM>. The entry temperature can be, for example, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some cases, the cold roll exit temperature can range from about <NUM> to about <NUM>. The exit temperature can be, for example, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM> to result in a gauge of about <NUM> or less (e.g., from about <NUM> to about <NUM> or from about <NUM> to about <NUM>). For example, the resulting gauge can be about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>.

The cold rolled coil can then be solutionized in a solution heat treatment step. The solutionizing can include heating the final gauge aluminum alloy from room temperature to a temperature of from about <NUM> to about <NUM> (e.g., from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>).

In certain aspects, the aluminum alloy product can then be cooled to a temperature of about <NUM> at a quench speed that can vary between about <NUM>/s to <NUM>/s in a quenching step that is based on the selected gauge. For example, the quench rate can be from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, from about <NUM>/s to about <NUM>/s, or from about <NUM>/s to about <NUM>/s. The quenching step can be performed using a liquid (e.g., water), a gas (e.g., air), or another selected quench medium.

Optionally, the aluminum alloy products described herein and cast by DC casting or CC and subsequently processed can be pretreated.

The pretreatment process described herein includes a step of applying a cleaner (also referred to herein as an entry cleaner or pre-cleaner) to one or more surfaces of the aluminum alloy product. The entry cleaner removes residual oils, or loosely adhering oxides, from the aluminum alloy product surface. Optionally, the entry cleaning can be performed using an alkaline solution having a pH of <NUM> or above. In some cases, the pH of the alkaline solution can be about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. The concentration of the alkaline agent in the alkaline solution can be from about <NUM> % to about <NUM> % (e.g., about <NUM> %, about <NUM> %, about <NUM> %, about <NUM> %, or about <NUM> % based on the volume of the alkaline solution). Suitable alkaline agents include, for example, silicates and hydroxides (e.g., sodium hydroxide). The alkaline solution can further include one or more surfactants, including for example anionic and non-ionic surfactants.

The pretreatment process described herein can also include a step of etching the surface of the aluminum alloy product. The surface of the aluminum alloy product can be etched using a chemical etch such as an acid etch (i.e., an etching procedure that includes an acid solution having a pH of less than <NUM>), an alkaline etch (i.e., an etching procedure that includes a basic solution having a pH of greater than <NUM>), or an etch under neutral conditions (i.e., an etching procedure that includes a neutral solution having a pH of <NUM>). The chemical etch prepares the surface to accept the subsequent application of a pretreatment. Any loosely adhering oxides, such as Al oxides and Mg rich oxides, entrapped oils, or debris, can be adequately removed during this step. Exemplary chemicals for performing the acid etch include sulfuric acid, hydrofluoric acid, nitric acid, phosphoric acid, and combinations of these. Exemplary chemicals for performing the alkaline etch include sodium hydroxide and potassium hydroxide. After the acid etching step, the surface of the aluminum alloy product can be rinsed with an aqueous or organic solvent.

A pretreatment can then be applied to the surface of the aluminum alloy product. Optionally, the pretreatment can include an adhesion promoter, a corrosion inhibitor, a coupling agent, an antimicrobial agent, or a mixture thereof. After the application of the pretreatment, the surface of the aluminum alloy product optionally can be rinsed with a solvent (e.g., an aqueous or an organic solvent). The surface of the aluminum alloy product can be dried after the rinsing step.

The aluminum alloy products and methods described herein can be used in automotive, electronics, and transportation applications, such as commercial vehicle, aircraft, or railway applications. For example, the aluminum alloy products can be used for chassis, cross-member, and intra-chassis components (encompassing, but not limited to, all components between the two C channels in a commercial vehicle chassis) to gain strength, serving as a full or partial replacement of high-strength steels. In certain examples, the aluminum alloy products can be used in the F, T4, T6, or T8x tempers.

In certain aspects, the aluminum alloy products and methods can be used to prepare motor vehicle body part products. For example, the disclosed aluminum alloy products and methods can be used to prepare automobile body parts, such as bumpers, side beams, roof beams, cross beams, pillar reinforcements (e.g., A-pillars, B-pillars, and C-pillars), inner panels, side panels, floor panels, tunnels, structure panels, reinforcement panels, inner hoods, or trunk lid panels. The disclosed aluminum alloy products and methods can also be used in aircraft or railway vehicle applications, to prepare, for example, external and internal panels.

The aluminum alloy products and methods described herein can also be used in electronics applications, to prepare, for example, external and internal encasements. For example, the aluminum alloy products and methods described herein can also be used to prepare housings for electronic devices, including mobile phones and tablet computers. In some examples, the aluminum alloy products can be used to prepare housings for the outer casing of mobile phones (e.g., smart phones) and tablet bottom chassis.

In certain aspects, the aluminum alloy products and methods can be used to prepare aerospace vehicle body part products. For example, the disclosed aluminum alloy products and methods can be used to prepare airplane body parts, such as skin alloys.

Aluminum alloy products are described throughout the text. The product may include monolithic materials, as well as non-monolithic materials such as roll-bonded materials, clad materials, or composite materials (such as but not limited to carbon fiber-containing materials). In some examples, the aluminum alloy product is a metal coil, a metal strip, a metal plate, a metal sheet, a metal billet, a metal ingot, or the like. In some examples, an alloying element, and/or an oxide thereof, as described herein can diffuse throughout the alloy product such that the concentration of the alloying element and/or oxide thereof is distributed throughout a full thickness (e.g., a bulk of the aluminum alloy) of the aluminum alloy product (i.e., at least within the subsurface and the bulk portions). For example, the aluminum alloy product can include a concentration of Mg and/or MgO that is distributed throughout the aluminum alloy product and can migrate to the subsurface portion during various processing steps, including homogenization, hot rolling, cold rolling, and solutionizing.

The aluminum alloy products described herein can have a surface roughness suitable for successful bonding according to any suitable bonding technique, including, for example, resistance spot welding. The aluminum alloy products described herein can have an average surface roughness of from about <NUM> nanometers (nm) to about <NUM>. For example, the aluminum alloy products described herein can have a surface roughness of about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>. , or anywhere in between.

Two samples of a 6xxx series aluminum alloy were prepared by direct chill casting and were processed by homogenizing, hot rolling, cold rolling, solution heat treating, air quenching, etching using <NUM>% R243, and pretreating with an adhesion promoter. The processing methods differed only by the solution heat treatment step. The first alloy sample was solution heat treated at <NUM> for <NUM> second (Method <NUM>) and the second alloy sample was solution heat treated at <NUM> for <NUM> seconds (Method <NUM>). <FIG> presents X-ray photoelectron spectroscopy (XPS) depth profile data for the Mg content in the sample prepared according to Method <NUM> (indicated by square symbols), the Mg content in the sample prepared according to Method <NUM> (indicated by triangle symbols), and the Mg content in a comparative 6xxx series aluminum alloy that was not solution heat treated ("AA 6xxx;" indicated by circle symbols). Evident in <FIG> is the ability to control migrant Mg concentrations in the subsurface and provide a uniform Mg concentration throughout the aluminum alloy product. Method <NUM> provided a more uniform Mg concentration from the surface to the bulk of the aluminum alloy with a greater Mg content compared to the comparative 6xxx series aluminum alloy. Method <NUM> provided a greater Mg content closer to the aluminum alloy surface and a lower Mg content in the bulk of the aluminum alloy, as well as a greater Mg content compared to the exemplary aluminum alloy prepared according to Method <NUM> and the comparative 6xxx series aluminum alloy. The comparative 6xxx series aluminum alloy exhibited a highly uniform Mg concentration from the surface to the bulk of the aluminum alloy and a lower overall Mg content near the surface of the aluminum alloy.

<FIG> presents XPS depth profile data for the Si content in the aluminum alloy product prepared according to Method <NUM> (indicated by square symbols), the aluminum alloy product prepared according to Method <NUM> (indicated by triangle symbols), and a comparative 6xxx series aluminum alloy that was not solution heat treated (indicated by circle symbols). Evident in <FIG> is the ability to control migrant silicon (Si) concentration in the bulk aluminum alloy and provide uniform Si concentration into the bulk of the aluminum alloy. Method <NUM> provided a greater Si content closer to the aluminum alloy surface and a lower Si content in the bulk of the aluminum alloy. Method <NUM> provided a greater Si content near the surface of the aluminum alloy and a more uniform Si concentration further into the bulk of the aluminum alloy. The Si content of the Method <NUM> alloy product was higher than that of the comparative 6xxx series aluminum alloy product. The comparative 6xxx series aluminum alloy exhibited a highly uniform and very low Si concentration from the surface to the bulk of the aluminum alloy and a lower overall Si content near the surface of the aluminum alloy.

<FIG> shows bond durability testing results of aluminum alloys prepare according to methods described herein. Exemplary aluminum alloy samples prepared according to Method <NUM> and Method <NUM> were bonded together and subjected to a stress durability test. In the stress durability test, a set of <NUM> lap joints/bonds were connected in sequence by bolts and positioned vertically in a <NUM>% relative humidity (RH) humidity cabinet. The temperature was maintained at <NUM>. A force load of <NUM> kN was applied to the bond sequence. The stress durability test is a cyclic exposure test that is conducted for up to <NUM> cycles. Each cycle lasts for <NUM> hours. In each cycle, the bonds are exposed in the humidity cabinet for <NUM> hours, then immersed in <NUM>% NaCl for <NUM> minutes, and finally air-dried for <NUM> minutes. Upon the breaking of three joints, the test is discontinued for the particular set of joints and is indicated as a first failure.

The exemplary aluminum alloy prepared according to Method <NUM> (left set of histograms) exhibited a lower cycles to failure number, indicating a lower bond durability than the exemplary aluminum alloy prepared according to Method <NUM> (right set of histograms). Mean cycles to failure is indicated by the left histogram in each set (hatched histogram) with first observed failure indicated by the right histogram in each set (cross-hatched).

Two samples of a 6xxx series aluminum alloy were prepared by direct chill casting and were processed by homogenizing, hot rolling, cold rolling, solution heat treating, air quenching, etching using <NUM>% R243, and pretreating with an adhesion promoter. The processing methods differed only by the hot rolling temperatures. The first alloy sample was hot rolled with a <NUM> hot mill exit temperature (Method <NUM>) and the second alloy sample was hot rolled with a <NUM> hot mill exit temperature (Method <NUM>). <FIG> shows the XPS depth profiling of the Mg content in the aluminum alloy product prepared by the high-temperature (Method <NUM>) versus the low-temperature (Method <NUM>) rolled surface. The aluminum alloy sample prepared according to Method <NUM> exhibited an enrichment ratio of <NUM> and an Mg concentration of <NUM> % within the aluminum alloy subsurface. The aluminum alloy prepared according to Method <NUM> exhibited an enrichment ratio of <NUM> and an Mg concentration of <NUM> % within the aluminum alloy subsurface.

Two samples of a 6xxx series aluminum alloy were prepared by direct chill casting and were processed by homogenizing, hot rolling, cold rolling, solution heat treating, air quenching, etching using <NUM>% R243, and pretreating with an adhesion promoter. The processing methods differed only by the order of the cleaning step. The first alloy sample was pre-cleaned before solution heat treatment (referred to as "Pre-clean -> SHT") and the second alloy sample was solution heat treated and then pre-cleaned (referred to as "SHT -> Pre-clean"). Both were followed by acid etching and pre-treatment application.

<FIG> presents XPS depth profile data of the Mg content in the aluminum alloy samples. The exemplary aluminum alloy cleaned before solutionizing (referred to as "Pre-clean → SHT") showed a <NUM> % Mg concentration and a <NUM> enrichment ratio. The exemplary aluminum alloy cleaned after solutionizing (referred to as "SHT → Pre-clean") showed a <NUM> % Mg concentration and a <NUM> enrichment ratio (not according to the invention).

Aluminum alloy products were prepared according to continuous casting methods as described above. The products were cast at a width of <NUM> and trimmed to <NUM>. The products were then hot rolled, cold rolled to <NUM>, annealed at <NUM> for <NUM> hours, and cold rolled to <NUM>. The products were then solutionized and quenched under varying conditions, as shown in Table <NUM>.

Surfaces of the aluminum alloy sheets were analyzed by glow discharge optical emission spectroscopy (GDOES). Amounts of magnesium (Mg), silicon (Si), copper (Cu), manganese (Mn), chromium (Cr), and iron (Fe) were analyzed. Measurements were conducted from the surface to a depth of <NUM>. Exemplary continuously cast aluminum alloy sheets are referred to as "C1," "C2," "C3," and "C4.

All samples were pretreated with an adhesion promoter (indicated by "PT"). A first surface of the aluminum alloy sheets (e.g., a surface contacting the belt of the caster) is indicated by "label. " A second analyzed surface (e.g., a surface not contacting the belt of the caster) is indicated by "unlabel. " Comparative DC cast aluminum alloys (referred to as "D1") were analyzed for comparison and effectiveness of continuously casting aluminum alloys for controlled enrichment of the surfaces of the aluminum alloy sheets.

<FIG> show GDOES data for Mg content near the surfaces of aluminum alloy sheets (e.g., from the surface to a depth of <NUM>). <FIG> shows data for Mg content extending into the bulk of the aluminum alloy sheet. <FIG> shows data for Mg content considered to be found in the surface of the aluminum alloy sheet (e.g., from the surface to a depth of <NUM>). <FIG> show a high diffusion of Mg to the surface of the aluminum alloy sheets produced by direct chill casting (samples D1 and D1-lab). <FIG> show decreased diffusion of Mg to the surface of the aluminum alloy sheets, and a uniform distribution of Mg from the surface into the bulk of the aluminum alloy sheets, produced by the exemplary continuous casting method described above. A lower concentration of Mg near the surface of the aluminum alloy sheets is desirable for bonding and joining applications.

<FIG> show GDOES data for Si content near the surfaces of aluminum alloy sheets (e.g., from the surface to a depth of <NUM>). <FIG> shows data for Si content extending into the bulk of the aluminum alloy sheet. <FIG> shows data for Si content considered to be found in the surface of the aluminum alloy sheet (e.g., from the surface to a depth of <NUM>). <FIG> show a high diffusion of Si to the surface of the aluminum alloy sheets produced by direct chill casting (samples D1 and D1-lab). <FIG> show decreased diffusion of Si to the surface of the aluminum alloy sheets, and a uniform distribution of Si from the surface into the bulk of the aluminum alloy sheets produced by the exemplary continuous casting method described above.

<FIG> show GDOES data for Cu content near the surfaces of aluminum alloy sheets (e.g., from the surface to a depth of <NUM>). <FIG> shows data for Cu content extending into the bulk of the aluminum alloy sheet. <FIG> shows data for Cu content considered to be found in the surface of the aluminum alloy sheet (e.g., from the surface to a depth of <NUM>). <FIG> show a low diffusion of Cu to the surface of the aluminum alloy sheets produced by direct chill casting (samples D1 and D1-lab). <FIG> show increased diffusion of Cu to the surface of the aluminum alloy sheets produced by the exemplary continuous casting method described above. Controlled diffusion of Cu to the surface of the aluminum alloy sheets can be desirable for bonding and joining applications.

<FIG> show GDOES data for Mn content near the surfaces of aluminum alloy sheets (e.g., from the surface to a depth of <NUM>). <FIG> shows data for Mn content extending into the bulk of the aluminum alloy sheet. <FIG> shows data for Mn content considered to be found in the surface of the aluminum alloy sheet (e.g., from the surface to a depth of <NUM>). <FIG> show no diffusion of Mn to the surface of the aluminum alloy sheets produced by direct chill casting (samples D1 and D1-lab). <FIG> show increased diffusion of Mn to the surface of the aluminum alloy sheets produced by the exemplary continuous casting method described above.

<FIG> show GDOES data for Cr content near the surfaces of aluminum alloy sheets (e.g., from the surface to a depth of <NUM>). <FIG> shows data for Cr content extending into the bulk of the aluminum alloy sheet. <FIG> shows data for Cr content considered to be found in the surface of the aluminum alloy sheet (e.g., from the surface to a depth of <NUM>). <FIG> show no diffusion of Cr to the surface of the aluminum alloy sheets produced by direct chill casting (samples D1 and D1-lab). <FIG> show increased diffusion of Cr to the surface of the aluminum alloy sheets produced by the exemplary continuous casting method described above. Controlled diffusion of Cr to the surface of the aluminum alloy sheets can be desirable for bonding and joining applications. Controlled diffusion of Cr to the surface of the aluminum alloy sheets can be desirable for corrosion resistance.

<FIG> show GDOES data for Fe content near the surfaces of aluminum alloy sheets (e.g., from the surface to a depth of <NUM>). <FIG> shows data for Fe content extending into the bulk of the aluminum alloy sheet. <FIG> shows data for Fe content considered to be found in the surface of the aluminum alloy sheet (e. g, from the surface to a depth of <NUM>). <FIG> show no diffusion of Fe to the surface of the aluminum alloy sheets produced by direct chill casting (samples D1 and D1-lab). <FIG> show increased diffusion of Fe to the surface of the aluminum alloy sheets produced by the exemplary continuous casting method described above.

Bond durability test results for the exemplary continuously cast aluminum alloy sheets and the comparative direct chill cast aluminum alloy sheets were performed according to the procedure described in Example <NUM>. For this experiment, the completion of <NUM> cycles indicates that the set of joints passed the bond durability test. The test results are shown below in Table <NUM>. In Table <NUM>, each of the joints are numbered <NUM> through <NUM>, where joint <NUM> is the top joint and joint <NUM> is the bottom joint when oriented vertically. The number in the cells, except for "<NUM>," indicates the number of successful cycles before a break. The number "<NUM> in a cell indicates that the joints remained intact for <NUM> cycles. The results are summarized in Table <NUM> below:.

For Trials <NUM>, <NUM>, and <NUM>, test coupons were cut from the exemplary continuously cast aluminum alloy sheets. The test coupons were subjected to alkaline and acid etching to clean and prepare the surfaces for bonding. Bonding was performed by pretreating the aluminum alloy sheets with an adhesion promoter and bonding the test coupons with an adhesive. Bonded test coupons were exposed to a humid environment for up to <NUM> duty cycles.

For Trial <NUM>, test coupons were cut from the exemplary continuously cast aluminum alloy sheets. The test coupons were subjected to a strong alkaline cleaning and acid etching to clean and prepare the surfaces for bonding. Bonding was performed by pretreating the aluminum alloy sheets with an adhesion promoter and bonding the test coupons with an adhesive. Bonded test coupons were exposed to a humid environment for up to <NUM> duty cycles.

For Trial <NUM>, test coupons were cut from the exemplary continuously cast aluminum alloy sheets. The test coupons were subjected to an acid etching to clean and prepare the surfaces for bonding. Bonding was performed by pretreating the aluminum alloy sheets with an adhesion promoter and bonding the test coupons with an adhesive. Bonded test coupons were exposed to a humid environment for up to <NUM> duty cycles.

For Trial <NUM>, test coupons were cut from the exemplary continuously cast aluminum alloy sheets. The test coupons were solution heat treated in the lab furnace and then subjected to alkaline and acid etching to clean and prepare the surface for bonding. Bonding was performed by pretreating the aluminum alloy sheets with an adhesion promoter and bonding the test coupons with an adhesive. Bonded test coupons were exposed to a humid environment for up to <NUM> duty cycles.

For Trial <NUM>, test coupons were cut from the comparative direct chill cast aluminum alloy sheets. The test coupons were subjected to acid etching to prepare the surface for bonding. Bonding was performed by pretreating the aluminum alloy sheets with an adhesion promoter and bonding the test coupons with an adhesive. Bonded test coupons were exposed to a humid environment for up to <NUM> duty cycles.

The exemplary continuously cast aluminum alloy sheets having controlled diffusion of Mn and Cr to the surface of the aluminum alloy sheets demonstrated excellent bond durability, surviving <NUM> test cycles without failure. The comparative direct chill cast aluminum alloy sheets having Mg diffused to the surface demonstrated poor bond durability.

Four samples of an AA5xxx series aluminum alloy were prepared by direct chill casting and were processed by homogenizing, hot rolling, cold rolling to a gauge of <NUM>, solution heat treating, air quenching, and etching using four different etchants. The etchants employed were (i) a mixture of phosphoric and sulfuric acid (referred to as solution "A" in Table <NUM> below), (ii) a mixture of sulfuric acid and ammonium fluoride (referred to as solution "B" in Table <NUM> below), (iii) a mixture of sulfuric acid and iron (III) sulfate hydrate (referred to as solution "C" in Table <NUM> below), and (iv) sodium hydroxide (referred to as solution "D" in Table <NUM> below). Sodium hydroxide (NaOH) was employed as a comparative control etchant due to its ability to remove any oxide layers from the subsurface.

<FIG> is a graph showing the RSW electrode service lifetime for RSW electrodes employed to weld aluminum alloy samples after etching in the various etchant solutions described above. Solution D (NaOH) was employed as a comparative control etchant as it is known in the art to completely remove a deformed oxide layer present on a rolled aluminum alloy product, particularly when the dwell time is at least <NUM> seconds (e.g., Etches <NUM> and <NUM> in Table <NUM>). As evident in the graph of <FIG>, Solution A (a mixture of phosphoric acid and sulfuric acid (H<NUM>PO<NUM>/H<NUM>SO<NUM>)) provided a RSW electrode lifetime of <NUM> welds, which is greater than the current industry demand of <NUM> welds. Additionally, in the example of <FIG>, the mixture of H<NUM>PO<NUM>/H<NUM>SO<NUM> provided an atomic concentration ratio of P/Mg of about <NUM> in a subsurface extending to a depth of about <NUM> from the surface of the aluminum alloy. Solution B (a mixture of sulfuric acid and ammonium fluoride (H<NUM>SO<NUM>/NH<NUM>F)) provided a RSW electrode lifetime of <NUM> welds when etched for <NUM> seconds, however a longer etch dwell time resulted in a loss of electrode lifetime. Solution C (a mixture of sulfuric acid and iron (III) sulfate hydrate (H<NUM>SO<NUM>/Fe<NUM>(SO<NUM>)<NUM>)) exhibited a poor performance, significantly reducing the RSW electrode lifetime. Thus, incorporating P into a Mg-containing subsurface significantly increased the RSW electrode lifetime.

<FIG> is a graph showing etch weight (i.e., amount of material removed from the surface of the aluminum alloys during etching) for each etch performed (Etches <NUM> - <NUM> in Table <NUM>). Evident in the graph of <FIG> and described above, Solution D was able to provide the greatest etch weight and was thus employed as a comparative solution. Of the etch solutions A, B, and C, Solution B provided the greatest etch weight and Solutions A and C provided similar etch weights, both less than that provided by Solution B. Referring to <FIG>, Solution B provided the greatest etch weight (see <FIG>) but did not exhibit improvement to the RSW electrode lifetime. Surprisingly, solutions A and C provided similar etch weights but also provided significantly different RSW electrode lifetimes. Particularly, Solution A (containing P) provided a significantly improved RSW electrode lifetime and Solution C was detrimental to the RSW electrode lifetime. Thus, removal of the deformed oxide layer alone is insufficient to improve the RSW electrode lifetime. Evident in <FIG>, removal of a portion of the deformed oxide layer, and a presence of a residual P concentration, can work in concert to improve the RSW electrode lifetime.

<FIG> are graphs showing glow discharge optical emission spectroscopy (GDOES) data for Mg content near the surface of the aluminum alloy samples described above (e.g., from the surface to a depth of <NUM>). <FIG> shows data for Mg content extending into the bulk of the aluminum alloy sample etched with Solution A. <FIG> shows data for Mg content extending into the bulk of the aluminum alloy sample etched with Solution B. <FIG> shows data for Mg content extending into the bulk of the aluminum alloy sample etched with Solution C.

<FIG> shows data for Mg content extending into the bulk of the aluminum alloy sample etched with Solution D. Not to be bound by theory, a Mg concentration found within the subsurface portion of the aluminum alloy samples can negatively impact the RSW electrode lifetime. Surprisingly, when the aluminum alloy samples were etched with Solution A (containing P), RSW electrode lifetime was significantly improved even though the sample contained a concentration of Mg within the subsurface of the aluminum alloy. The aluminum alloy sample etched with comparative Solution D (<FIG>) exhibited nearly complete removal of Mg near the surface of the aluminum alloy, further indicating that the presence of Mg and/or a Mg containing compound (e.g., MgO) after etching with a P containing compound provides a significantly improved RSW electrode lifetime.

Further, <FIG> shows the GDOES data for the aluminum alloy sample etched with Solution C. Evident in the graph of <FIG>, Mg and/or Mg containing compounds are present near the surface of the aluminum alloy samples; however, Solution C did not contain P and was detrimental to the RSW electrode lifetime (see <FIG>). Thus, the presence of Mg and/or Mg containing compounds near the surface of the aluminum alloy without having P present in the etching solution can be detrimental to the RSW electrode lifetime.

In some aspects, alloying element and/or alloying element oxide particle size and morphology can affect surface properties of the aluminum alloy product. For example, <FIG>, <FIG>, <FIG>, and <FIG> present scanning electron microscope (SEM) micrographs of the aluminum alloy samples described above. <FIG> show SEM micrographs of the aluminum alloy samples etched using Solution A. <FIG> show the SEM micrographs from Etch <NUM> (see Table <NUM>). <FIG> show the SEM micrographs from Etch <NUM>. <FIG> are micrographs from a scanning electron mode. <FIG> are micrographs from a back-scattered electron mode. <FIG> shows SEM micrographs of the aluminum alloy samples etched using Solution B. <FIG> show the SEM micrographs from Etch <NUM>. <FIG> show the SEM micrographs from Etch <NUM>. <FIG> are micrographs from a scanning electron mode. <FIG> are micrographs from a back-scattered electron mode. <FIG> shows SEM micrographs of the aluminum alloy samples etched using Solution C. <FIG> show the SEM micrographs from Etch <NUM>. <FIG> show the SEM micrographs from Etch <NUM>. <FIG> are micrographs from a scanning electron mode. <FIG> are micrographs from a back-scattered electron mode. <FIG> shows SEM micrographs of the aluminum alloy samples etched using Solution D. <FIG> show the SEM micrographs from Etch <NUM>. <FIG> show the SEM micrographs from Etch <NUM>. <FIG> are micrographs from a scanning electron mode. <FIG> are micrographs from a back-scattered electron mode. Evident in <FIG>, Solution B (<FIG>) provided the greatest etch weight of Etch Solutions A, B, and C, see <FIG>), thus providing a surface having a reduced amount of Mg and/or Mg containing compound particles (indicated by bright spots in <FIG>, <FIG>, and <FIG>), and a reduced deformed oxide layer (shown as darker grey areas in <FIG>, <FIG>, and <FIG>).

A commercially produced AA5182 aluminum alloy sheet having a thickness of <NUM> was used in an as-produced condition (meaning the aluminum alloy sheet was not etched according to the methods described herein). The aluminum alloy sheet was subjected to a RSW trial. <FIG>, Panel A shows a copper RSW electrode tip. In the example of <FIG>, Panel A, MgO particles <NUM> adhered to the RSW electrode tip. <FIG>, Panel B shows a micrograph of the weld, and <FIG>, Panel C is a higher magnification image of <FIG>, Panel B. As shown in <FIG>, Panel C, dark areas <NUM> indicate MgO present at the surface or in the subsurface of the aluminum alloy sheet. In the example of <FIG>, Panel C, the Mg content was <NUM> %. An as-produced AA5182 aluminum alloy contains from <NUM> % to <NUM> % Mg (e.g., about <NUM> % Mg). A Mg content of <NUM> % at the surface or in the subsurface indicated migration of Mg from a bulk of the aluminum alloy toward the surface during processing, providing undesired amounts of MgO at the surface or in the subsurface of the aluminum alloy. Accordingly, during the RSW trial, MgO particles adhered to the RSW electrode tip. Such MgO particle pick-up can significantly reduce the RSW electrode lifetime. Thus, etching and/or cleaning the surface of the aluminum alloy sheet according to the methods described herein can remove MgO from the surface or the subsurface of the aluminum alloy, form Mg-P compounds as described above, eliminate MgO pick-up by the RSW electrode, and increase the lifetime of the RSW electrode.

<FIG> is a graph showing the yellow index (YI) of the aluminum alloy samples prepared as described above. As described above, the YI can indicate the presence of a Mg and/or Mg containing compound (e.g., MgO) on the surface of the aluminum alloys. A lack of a significant YI is indicated by a dashed line (e.g., a YI less than about <NUM>). The aluminum alloy samples etched using comparative Solution D (e.g., providing the greatest etch weight) exhibited a very low YI, particularly when the etching dwell time was greater than <NUM> seconds (e.g., Etches <NUM>, <NUM>, and <NUM>, see Table <NUM>). A very low YI indicates a negligible concentration of Mg or Mg containing compounds on the surface of the aluminum alloys. Additionally, the aluminum alloy samples etched using Solution B (e.g., providing the greatest etch weight of the exemplary etch solutions (Solutions A, B, and C)) exhibited a low YI, indicating a significant removal of Mg and/or Mg containing compounds from the surface of the aluminum alloy samples. The aluminum alloy samples etched using Solutions A and C (e.g., providing low etch weights) exhibited a greater YI for each sample, indicating a greater Mg and/or Mg containing compounds concentration than the aluminum alloy samples etched using Solutions B and D. Surprisingly, the aluminum alloy samples etched using Solution A provided a significantly improved RSW electrode lifetime even while having a significant Mg and/or Mg containing compounds concentration at the surface of the aluminum alloy samples. Also, an increase in the YI was observed from Etch Reference No. <NUM> to Etch Reference No. <NUM> (e.g., a "reverse effect" was observed), indicating the etch procedure exposed additional Mg to the alloy surface and thus oxidizing the additional Mg once exposed. Additional Mg can be attributed to a Mg enriched subsurface. Surprisingly, the aluminum alloy samples etched using Solution C exhibited detrimental effects on the RSW electrode lifetime when exhibiting a similar YI to the aluminum alloy samples etched using Solution A. Thus, an optimized surface chemistry, wherein a lower etch weight allows for a concentration of Mg and/or Mg containing compounds to remain within the subsurface of an aluminum alloy, created by etching with a P containing compound in which residual P can remain, provided a significantly improved RSW electrode lifetime. The standard deviation of the YI for all samples was less than <NUM>% of the mean YI.

<FIG> is a graph showing the surface roughness of the aluminum alloy samples prepared as described above. The aluminum alloy samples etched using Solutions A and C (e.g., providing low etch weights) exhibited a negligible change in surface roughness with increasing etch time for each sample, indicating a more uniform etch (i.e., a more uniform removal of surface material) regardless of etch time when compared to the aluminum alloy samples etched using Solutions B and D. Surprisingly, the aluminum alloy samples etched using Solution A provided a significantly improved RSW electrode lifetime even while having a lower surface roughness compared to the aluminum alloy samples etched using Solutions B and D, in particular, Etch Reference Nos. <NUM>, <NUM>, <NUM>, and <NUM>.

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 scope of the present invention as defined in the following claims.

Illustration <NUM> is an aluminum alloy product prepared according to the method of any preceding or subsequent illustration, wherein the aluminum alloy product comprises a motor vehicle body part, an aerospace body part, a transportation body part, a marine body part, a motor vehicle panel, an aerospace skin panel, a marine panel, an electronics device housing, an architectural structural part, or an architectural aesthetic panel.

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. During the studies described in the following examples, conventional procedures were followed, unless otherwise stated. Some of the procedures are described below for illustrative purposes.

<FIG> presents XPS depth profile data of the Mg content in the aluminum alloy samples. The exemplary aluminum alloy cleaned before solutionizing (referred to as "Pre-clean → SHT") showed a <NUM> % Mg concentration and a <NUM> enrichment ratio. The exemplary aluminum alloy cleaned after solutionizing (referred to as "SHT -> Pre-clean") showed a <NUM> % Mg concentration and a <NUM> enrichment ratio.

Claim 1:
An aluminum alloy product, comprising:
a subsurface portion having a concentration of a migrant element, wherein the subsurface portion extends from the surface to a depth of <NUM> within the interior of the alloy product and wherein the migrant element comprises Mg, Si, Cu, Mn, Cr and/or Fe; and
a bulk portion having a concentration of the migrant element,
wherein the concentration of the migrant element in the subsurface portion is higher than the concentration of the migrant element in the bulk portion, and
wherein the aluminum alloy product has a high enrichment ratio of migrant elements Cr, Mn and/or Fe of <NUM> or greater and has a low enrichment ratio for one or more migrant elements from Mg, Si and Cu of <NUM> to <NUM>, wherein the enrichment ratio is a ratio of the atomic concentration of the migrant element in the subsurface portion to the atomic concentration of the migrant element in the bulk portion.