CN116457121A

CN116457121A - Composition gradient direct chill cast aluminum ingot to achieve reduced cracking

Info

Publication number: CN116457121A
Application number: CN202180066957.4A
Authority: CN
Inventors: S·R·瓦格斯塔夫; K·桑达拉姆
Original assignee: Novelis Inc Canada
Current assignee: Novelis Inc Canada
Priority date: 2020-10-01
Filing date: 2021-09-23
Publication date: 2023-07-18
Also published as: EP4221914A1; DE212021000471U1; JP2023543872A; KR20230044504A; CA3193262A1; MX2023003488A; US20230256503A1; WO2022072206A1

Abstract

Methods of making compositionally graded aluminum alloy products are described. The method may include casting the composite ingot in a mold. The composite ingot may comprise: an inner region comprising a first aluminum alloy; an outer region surrounding the inner region; and a composition gradient region between the inner region and the outer region. The outer region may include a second aluminum alloy different from the first aluminum alloy. At least one alloying element of the first aluminum alloy may have a decreasing content throughout the composition gradient zone in a direction from the inner zone to the outer zone. Aluminum alloy composite ingots and rolled aluminum alloy products having the composition gradient zone are also described.

Description

Composition gradient direct chill cast aluminum ingot to achieve reduced cracking

Cross Reference to Related Applications

The present application claims the benefit and priority of U.S. provisional application No. 63/198,184, filed on 1 month 10 in 2020, which provisional application is incorporated herein by reference in its entirety.

Technical Field

The present disclosure relates generally to metallurgy, and more particularly to aluminum alloy products and aluminum alloy ingot casting and processing techniques.

Background

Aluminum alloy ingots may be cast using direct-chill (DC) casting. However, some metals or alloys may spontaneously fracture due to edge cracking or experience substantial damage (such as cold cracking) during or after casting into ingots. Certain metals or alloys may experience cold cracking during or after casting due to the combination of brittle microstructures, microporosity, and thermal stresses formed during DC casting. High strength alloy products are particularly susceptible to failure due to cold cracking stresses formed during casting because (i) the rich nature of their composition results in the grains being surrounded by brittle eutectic and/or porous products, providing an off-the-shelf intergranular fracture mechanism through grain boundaries after crack initiation, and (ii) the difference in volume shrinkage of specific alloying elements during solidification makes the stresses greater for more dilute alloys. These susceptibility to failure may benefit from the use of specific mold shapes to prevent cold cracking. The effect of cold cracking is observable, for example, when cooled to below about 480 ℃. Another problem encountered with DC casting techniques includes edge cracking. Edge cracking may be caused by grain boundary melting caused by alkali elements such as sodium (Na). Edge cracking may also be caused by positive macrosegregation on the ingot edge, where positive segregation is higher at the short sides of the ingot as the width of the ingot increases. When large macrosegregation is present, normal homogenization heat treatment practices may be inadequate, causing melting of severely segregated edges and edge cracking during hot rolling. Cold and edge cracking cause recovery and handling time loss, as well as safety issues including cracking or hot tearing in the pulled ingot. The present disclosure addresses the problems of cold cracking and edge cracking by forming a composition gradient over the outer region of the ingot.

Disclosure of Invention

The term embodiment and similar terms are intended to broadly refer to all subject matter of the present disclosure and appended claims. Statements containing these terms should not be construed as limiting the subject matter described herein or limiting the meaning or scope of the appended claims. The embodiments of the disclosure encompassed herein are defined by the appended claims rather than the summary of the invention. This summary is a high-level overview of aspects of the present disclosure and introduces some concepts that are further described in the detailed description section that follows. 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 of this disclosure, any or all of the accompanying drawings, and each claim.

In one aspect, a method of making a compositionally graded aluminum alloy product is described. One method of this aspect may include casting a composite ingot in a mold. The composite ingot may comprise: an inner region comprising a first aluminum alloy; an outer region surrounding the inner region, the outer region comprising a second aluminum alloy different from the first aluminum alloy; and a composition gradient region between the inner region and the outer region. The at least one alloying element of the first aluminum alloy may have a decreasing content throughout the composition gradient zone in a direction from the inner zone to the outer zone.

In embodiments, the method may include casting the first aluminum alloy and the second aluminum alloy simultaneously, such as during all or part of the casting process. In some cases, casting of the first aluminum alloy (inner region) may begin before casting of the second aluminum alloy (outer region) begins. In some cases, casting of the second aluminum alloy (outer region) may begin before casting of the first aluminum alloy (inner region) begins. In embodiments, the method may include delivering a first aluminum alloy from a first elevation to the mold, and delivering a second aluminum alloy from a second elevation to the mold, wherein the second elevation is different from the first elevation.

In embodiments, the method may further comprise peeling the composite ingot to remove at least a portion of the composition gradient zone and the outer zone from the rolling surface. The stripping may include removing material to produce a monolithic ingot comprising the first aluminum alloy.

In embodiments, the first aluminum alloy may include a 7xxx series aluminum alloy, a 5xxx series aluminum alloy, or a 2xxx series aluminum alloy. The first aluminum alloy may include 7075 aluminum alloy, 5182 aluminum alloy, or 2024 aluminum alloy. In embodiments, the second aluminum alloy may include a 1xxx series aluminum alloy. The second aluminum alloy can have a purity of, for example, at least 99.7%.

In embodiments, the at least one alloying element of the first aluminum alloy may include Zn, cu, mg, or Na. In embodiments, the outer region may be substantially free of the at least one alloying element.

In embodiments, the composite ingot may be substantially free of cracking. The crack may include, for example, a cold crack, a heat crack, an edge crack, or a tail crack. Additionally or alternatively, the composite ingot may not experience cracking, for example, during a hot rolling process. In embodiments, the composite ingot may be substantially free of porous structures. For example, the porous structure may include pores that are nucleation sites from fracture during hot rolling.

In embodiments, casting the composite ingot may include a direct chill casting process, wherein the inner region and the outer region are co-cast in an arrangement wherein the outer region is in contact with cooling water.

In embodiments, the outer region may have a thickness of 7% to 15% of the total thickness of the composite ingot. In embodiments, the compositional gradient region may have a thickness of 2% to 10% of the total thickness of the composite ingot.

The method of this aspect may include additional process steps. For example, a rolled aluminum alloy product may be formed by the methods described herein. In embodiments, a method of this aspect may further comprise processing the monolithic ingot to form an aluminum alloy sauter plate, or sheet comprising the first aluminum alloy. The method of this aspect may further comprise one or more of a homogenization process, a hot rolling process, a cold rolling process, an annealing process, a solution heat treatment process, a quenching process, or a surface treatment process.

In an embodiment, the method may further comprise directing a magnetic field during casting, the magnetic field configured to suppress turbulence in a direction perpendicular to the composition gradient zone. In embodiments, the method may further comprise directing the magnetic field during casting to inhibit turbulence in a direction perpendicular to the compositional gradient region. Guiding may include, for example, positioning the magnetic field at a height between the first height and the second height. In embodiments, the method may further comprise directing the magnetic field during casting to inhibit turbulence in a direction perpendicular to the compositional gradient region. Guiding the magnetic field may include, for example, providing a slag dam positioned at a height between the first height and the second height within the melt body.

In another aspect, an aluminum alloy composite ingot is described. In some embodiments, aluminum alloy composite ingots may be prepared by the methods described herein. The aluminum alloy composite ingot may include: an inner region comprising a first aluminum alloy; an outer region surrounding the inner region; and a composition gradient region between the inner region and the outer region. The outer region may comprise a second aluminum alloy different from the first aluminum alloy. The at least one alloying element of the first aluminum alloy may have a decreasing content throughout the composition gradient zone in a direction from the inner zone to the outer zone.

In embodiments, the first aluminum alloy may include a 7xxx series aluminum alloy, a 5xxx series aluminum alloy, or a 2xxx series aluminum alloy. The first aluminum alloy may include 7075 aluminum alloy, 5182 aluminum alloy, or 2024 aluminum alloy. In embodiments, the second aluminum alloy may include a 1xxx series aluminum alloy. The second aluminum alloy can have a purity of, for example, at least 99.7%. Optionally, the at least one alloying element of the first aluminum alloy may include Zn, cu, mg, or Na. In embodiments, the outer region may be substantially free of the at least one alloying element.

In embodiments, the composite ingot may be substantially free of cracking, such as free of cold cracking, hot cracking, edge cracking, and/or tail cracking, and may optionally not experience cracking during rolling. In embodiments, the composite ingot may be substantially free of porous structures. The porous structure may include pores as nucleation sites from fracture during hot rolling.

In another aspect, a rolled aluminum alloy product is described. The rolled aluminum alloy product may include: an inner region comprising a first aluminum alloy; an outer region surrounding the inner region; and a composition gradient region between the inner region and the outer region. The outer region may comprise a second aluminum alloy different from the first aluminum alloy. The at least one alloying element of the first aluminum alloy may have a decreasing content throughout the composition gradient zone in a direction from the inner zone to the outer zone.

In embodiments, a rolled aluminum alloy product may be made from an ingot described herein, such as an aluminum alloy composite ingot. In embodiments, the first aluminum alloy may include a 7xxx series aluminum alloy, a 5xxx series aluminum alloy, or a 2xxx series aluminum alloy. The first aluminum alloy may include 7075 aluminum alloy, 5182 aluminum alloy, or 2024 aluminum alloy. In embodiments, the second aluminum alloy may include a 1xxx series aluminum alloy. The second aluminum alloy can have a purity of at least 99.7%. In embodiments, the at least one alloying element of the first aluminum alloy may include Zn, cu, mg, or Na. In embodiments, the outer region may be substantially free of the at least one alloying element.

Other objects and advantages will be apparent from the following detailed description of non-limiting examples.

Drawings

The specification makes reference to the following drawings wherein the use of the same reference number in different drawings is intended to illustrate the same or similar components.

FIG. 1 provides a schematic illustration of a direct chill cast composition gradient aluminum alloy product.

FIG. 2 provides a schematic illustration of direct chill casting the compositionally graded aluminum alloy product of FIG. 1 as processing continues.

FIG. 3 provides a schematic illustration of direct chill casting the compositionally graded aluminum alloy product of FIG. 2 as processing continues.

FIG. 4 provides a schematic illustration of direct chill casting the compositionally graded aluminum alloy product of FIG. 3 as processing continues.

Fig. 5A provides a cross-sectional view of a compositionally graded aluminum alloy product, such as made in accordance with fig. 1-4.

Fig. 5B provides a schematic diagram of region a of fig. 5A in more detail.

Fig. 6 provides a perspective view of a compositionally graded aluminum alloy product, such as made in accordance with fig. 1-4.

FIGS. 7A and 7B provide schematic illustrations of the skinning of a compositionally graded aluminum alloy product by a method employing a band saw type apparatus and a mill type apparatus, respectively.

Fig. 8A and 8B provide schematic illustrations of a compositionally graded aluminum alloy product prior to skinning (fig. 8A) and after skinning (fig. 8B).

FIG. 9 provides a schematic illustration of a composition gradient aluminum alloy product that has been peeled and processed into a monolithic ingot to produce an aluminum alloy product.

FIG. 10A provides a schematic illustration of a composition gradient aluminum alloy product and a processed ingot that has been partially peeled, for example, using edge peeling, to produce an aluminum alloy product.

Fig. 10B provides a schematic illustration of a composition gradient aluminum alloy product and a processed ingot that has been partially stripped, for example, using rolling surface stripping, to produce an aluminum alloy product.

FIG. 11 provides a schematic illustration of a compositionally graded aluminum alloy product that has not yet been peeled or sawn apart, and the manufacture and processing of ingots to produce aluminum alloy products.

Detailed Description

Described herein are compositionally graded aluminum alloy products, methods of making and using compositionally graded aluminum alloy products, and products formed from compositionally graded aluminum alloy products. The disclosed compositionally graded aluminum alloy products include aluminum alloys that address two issues that may occur when using Direct Chill (DC) casting techniques, namely edge cracking issues such as in a hot mill and/or cold cracking or brittle fracture events in freshly cast ingots during or after casting. The compositionally graded aluminum alloys described herein are suitable for Direct Chill (DC) casting techniques for making alloys such as aluminum alloys having a high ductile-brittle transition temperature (e.g., greater than or about 200 ℃, greater than or about 300 ℃, or up to about 400 ℃), aluminum alloys susceptible to hot tearing during casting, and aluminum alloys that may experience brittle fracture events during casting.

For example, certain alloys may be difficult to cast into ingots due to internal stresses formed during casting due to thermal shrinkage that occurs during cooling of the ingot by applying a cooling fluid directly onto the surface of the ingot. In some cases, brittle aluminum alloy ingots directly cast using DC casting techniques may spontaneously experience catastrophic fracture and cracking as a portion of the ingot cools to or below the ductile-brittle transition temperature, thereby causing damage, safety hazards, reduced cast product recovery, and manufacturing downtime for allowing the damaged components and materials to be cleaned, recovered, and repaired. Some aluminum alloys cast directly using DC casting may similarly experience hot tearing, which may cause similar safety and cleaning problems and low recovery. The techniques described herein provide a method of reliably obtaining aluminum alloy ingots of such aluminum alloys that may be difficult to cast directly using DC casting techniques.

The disclosed technology simultaneously casts an aluminum alloy with a DC casting technique having an inner region comprising a first aluminum alloy, an outer region surrounding the inner region and comprising a second aluminum alloy different from the first aluminum alloy, and a composition gradient zone between the inner and outer regions. The disclosed techniques may also employ a process in which the composite ingot may be optionally skinned to remove at least a portion of the compositional gradient zone and/or the outer zone. For example, the disclosed techniques may include fully stripping the composition gradient region and the outer region to produce a monolithic ingot comprising an aluminum alloy that is difficult to cast. For example, the disclosed techniques may include stripping the composition gradient region and the outer region to produce a composite ingot comprising an aluminum alloy that is difficult to cast, wherein the gradient region surrounds the inner region.

Techniques for twin casting different aluminum alloys to form composite ingots having inner and outer regions and a compositional gradient region therebetween can introduce significant complexity, difficulty, and cost as compared to direct chill casting of monolithic ingots. For example, additional and more complex processes and equipment may be used, including additional furnaces, additional molten aluminum alloy processing equipment, more complex casting equipment, and the like.

The process of stripping the outer region from the composite ingot may also introduce additional complexity, time and equipment requirements compared to direct chill casting of monolithic ingots. For example, a peeling machine may be used, and a machine for moving, turning or rotating the composite ingot may be used, depending on the peeling configuration. The peeling process may also take a significant amount of time, resulting in reduced throughput.

Furthermore, peeling the outer region from the composite ingot may also result in a relatively high energy usage and necessary disposal or recovery of the peeled material. For example, the thermal requirements of the additional furnace required to melt the aluminum alloy in the outer region may be significant. Because the aluminum alloy from the outer zone may be skinned during the process of forming a monolithic ingot from the composite ingot, the energy required to heat and prepare the outer zone may be considered wasted in some embodiments. Increasing energy usage and wasting energy is undesirable in aluminum alloy and alloy ingot casting processes, and may often make such processes impractical or otherwise undesirable. The debarking may also create additional excess material to be disposed of or recycled in the form of the outer region being debarked, and the recycling or disposal process may add additional complexity and energy usage requirements. In some cases, the peeled material may include a portion of the inner zone aluminum alloy, and thus recovery of the peeled material may be complicated by having to handle two different alloy compositions in the peeled material.

Both complexity and additional energy and thermal requirements present disadvantages to the disclosed techniques for manufacturing monolithic aluminum alloy ingots by first casting a composite ingot followed by peeling one or more outer layers. Furthermore, co-casting techniques for composite ingots, such as those described in U.S. patent nos. 7,748,434 and 8,927,113, focus on how to add material as a cladding layer on the exterior of the ingot, and thus the stripping of this additional cladding material layer directly violates the intended purpose of the technique for co-casting of composite ingots. However, for certain aluminum alloys, the disclosed techniques have unexpected advantages in that they allow monolithic ingots, such as monolithic ingots of brittle aluminum alloys and aluminum alloys subject to hot tearing and spontaneous cracking, to be formed in a safe and reliable manner and that minimizes or reduces the problems associated with directly casting monolithic ingots of brittle aluminum alloys. Recovery of monolithic aluminum alloy ingots in this manner may be superior to aluminum alloy ingots using other methods (which may be more or less complex) to form aluminum alloys that are difficult to cast. In some cases, monolithic aluminum alloy ingots formed in accordance with the present disclosure may be significantly larger than those formed using other methods that may also be more or less complex than the methods disclosed herein.

Definition and description:

as used herein, the terms "invention," "the invention," "this invention," and "the invention" are intended to broadly refer to all subject matter of this patent application and the appended claims. Statements containing these terms should not be construed as limiting the subject matter described herein or limiting the meaning or scope of the appended patent claims.

In the specification, reference is made to alloys identified by AA number and other related designations (such as "series" or "7 xxx"). It is to be understood that the numbering and naming system most commonly used for naming and identifying aluminum and its alloys is referred to as "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" issued by the aluminum association (The Aluminum Association).

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

As used herein, a sauter board (also referred to as a sheet board) typically has a thickness of about 4mm to about 15 mm. For example, the sauter board can have a thickness of about 4mm, about 5mm, about 6mm, about 7mm, about 8mm, about 9mm, about 10mm, about 11mm, about 12mm, about 13mm, about 14mm, or about 15 mm.

As used herein, sheet generally refers to aluminum products having a thickness of less than about 4 mm. For example, the sheet may have a thickness of less than about 4mm, less than about 3mm, less than about 2mm, less than about 1mm, less than about 0.5mm, or less than about 0.3mm (e.g., about 0.2 mm).

"ductile-brittle transition temperature" refers to a temperature at which the fracture energy of a metal alloy is below a predetermined value, such as determined according to impact testing (see, e.g., ASTM a370-19e1,Standard Test Methods and Definitions for Mechanical Testing of Steel Products,ASTM International,West Conshohocken,PA,2019, incorporated herein by reference). In some embodiments, ductile-brittle transition temperature refers to the temperature at which ductile changes in the metal alloy are observed, below which the metal alloy exhibits more brittle characteristics, and above which the metal alloy exhibits more ductile characteristics. For example, at temperatures below the ductile-brittle transition temperature of the metal alloy, a particular or standard magnitude of impact may cause the metal alloy to fracture, while at temperatures above the ductile-brittle transition temperature of the metal alloy, a particular or standard magnitude of impact may instead cause the metal alloy to deform rather than fracture. In some cases, during casting of a metal alloy ingot, the surface of the ingot may be exposed to a cooling fluid (e.g., water) while the center of the ingot may remain at a high temperature. Stresses and strains may occur within the ingot due to non-uniform temperature distribution and temperature dependent thermal expansion/contraction of the ingot. If the ductile-brittle transition temperature of the metal alloy is too high, the ingot may spontaneously fracture due to stresses and strains formed during cooling of the ingot.

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

All ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a specified range of "1 to 10" should be considered to include any and all subranges between (and including 1 and 10) the minimum value of 1 and the maximum value of 10; that is, all subranges start with a minimum value of 1 or more (e.g., 1 to 6.1) and end with a maximum value of 10 or less (e.g., 5.5 to 10). Unless otherwise indicated, when referring to the compositional amount of an element, the expression "up to" means that the element is optional and includes zero percent composition of that particular element. All compositional percentages are weight percentages (wt.%) unless otherwise indicated.

As used herein, the meaning of "a" and "an" and "the" include singular and plural referents unless the context clearly dictates otherwise.

Methods of using the disclosed aluminum alloys and aluminum alloy products

The aluminum alloys and aluminum alloy products described herein, such as aluminum alloy ingots, as well as rolled aluminum alloy products, are useful in automotive applications and other transportation applications, including aircraft and railway applications. For example, the disclosed aluminum alloy products can be used to make shaped aluminum products and automotive structural components, such as bumpers, side rails, roof rails, cross rails, pillar reinforcements (e.g., a-pillars, B-pillars, and C-pillars), interior panels, exterior panels, side panels, interior covers, exterior covers, or trunk lids. The aluminum alloy products and methods described herein can also be used in aircraft or rail vehicle applications to make, for example, exterior and interior panels.

The aluminum alloy products and methods described herein may also be used in electronic applications. For example, the aluminum alloy products and methods described herein can be used to prepare housings for electronic devices, including mobile phones and tablet computers. In some examples, aluminum alloy products may be used to prepare covers for mobile phones (e.g., smart phones), tablet chassis, and other portable electronic devices. The aluminum alloy products and methods described herein can also be used in other applications as desired.

Method for producing alloys and alloy products

The aluminum alloys and aluminum alloy products described herein can be cast using any suitable casting method known to those of ordinary skill in the art. As a non-limiting example, the casting process may include a direct-cooled (DC) casting process.

The outer region of the first aluminum alloy may surround the inner region of the second aluminum alloy, with a composition gradient zone between the outer region and the inner region, as described herein, forming a composition gradient aluminum alloy product. The composition gradient zone has at least one alloying element present in the first aluminum alloy from the inner zone, the content of which decreases throughout the composition gradient zone in a direction from the inner zone to the outer zone, as will be described in detail below. The casting of the first aluminum alloy and the second aluminum alloy may be performed simultaneously or at least partially simultaneously. The initial and final dimensions of the compositionally graded aluminum alloy products described herein may be determined by the desired characteristics of the overall final product.

The cast ingot or other cast product may be processed by any suitable means. Optionally, these processing steps can be used to prepare sheets. Such processing steps include, but are not limited to, homogenization, hot rolling, cold rolling, solution heat treatment, and optional pre-aging steps. The individual rolling steps may optionally be separated by other processing steps including, for example, annealing steps, cleaning steps, heating steps, cooling steps, and the like.

FIG. 1 provides a schematic illustration of a direct chill casting composition gradient aluminum alloy product by providing different molten aluminum alloys 105 and 115 to form a composite ingot. The aluminum alloys mentioned herein may optionally be replaced with other alloys such as steel, magnesium alloys, copper alloys, and the like. The direct chill casting technique shown in fig. 1 may be used to form a compositionally graded aluminum alloy product having an inner region surrounded by an outer region, wherein the inner and outer regions each comprise a different aluminum alloy. The technique of fig. 1 is also referred to herein as a simultaneous twin casting technique. As shown, the molten aluminum alloys 105 and 115 are cast in a vertical casting arrangement, where they may be allowed to contact each other in a molten and/or partially molten configuration, and cooled by cooling water 130. This technique may be used to form a composite ingot comprising aluminum alloys 110 and 120, which may then be further processed. Fig. 1 shows an initial stage of casting in which molten aluminum alloy 105 is provided prior to molten aluminum alloy 115. Alternatively, the molten aluminum alloy 115 may be provided prior to the molten aluminum alloy 105, or the molten aluminum alloy 105 and the molten aluminum alloy 115 may be provided simultaneously. The molten aluminum alloy 105 is poured into a shallow mold 160 mounted on a bottom block 170 on a hydraulic table 180 to form a living bottom of the mold, thereby expanding the volume of an ingot formed during the casting process. As the mold fills to a greater volume and begins to solidify, the bottom block 170 may decrease at a controlled rate. As molten aluminum is provided to the mold 160, the volume of alloy increases to form an ingot.

FIG. 2 provides a schematic illustration of direct chill casting the compositionally graded aluminum alloy product of FIG. 1 as processing continues. The molten aluminum alloy 105 may continue to be cast concurrently with the molten aluminum alloy 115. Molten aluminum alloy 115 forms inner zone aluminum alloy 120, while molten aluminum alloy 105 forms outer zone aluminum alloy 110. Molten aluminum casting may use a combination of bags or screens to direct molten metal. Mesh, screen and combination bag are terms used interchangeably herein. The net is used to achieve a limited amount of turbulence so that the flow of molten metal is redirected perpendicular to the casting direction, in other words parallel to the desired interface plane. By controlling the flow rate, turbulence is minimized. The web 145 for receiving the molten aluminum alloy 105 is at a first height h ₁ . The mesh 155 for receiving the molten aluminum alloy 115 is at a second height h ₂ . Height h ₁ And h ₂ Relative to the mold surface 165 of the mold 160. Height h ₁ And height h ₂ May be the same or different. As shown in fig. 2, a height h ₂ Can be smaller than height h ₁ Without being bound by any theory, this may help promote the formation of the inner region.

Alternatively, a magnetic field may be used to suppress turbulence in a direction perpendicular to the composition gradient zone. The correctly oriented static magnetic field may provide a selected velocity vector that may be used to promote the formation of biliquid layers and inhibit mixing. One way is to apply a magnetic field at a height between the heights of the two nets receiving the liquid during casting so that turbulence and mixing of the two molten aluminum alloys is stopped or at least suppressed. Alternatively, a slag dam may be used to suppress turbulence and minimize mixing of the two molten aluminum alloys. The slag dams may be rectangular or other shape suitable for placement in the melt at a level below the net. The slag dams may be made of ceramic refractory material.

FIG. 3 provides a schematic illustration of direct chill casting the compositionally graded aluminum alloy product of FIG. 2 as processing continues. The volume of the inner zone aluminum alloy 120 increases and the outer zone aluminum alloy 110 is pushed outward from the center of the inner zone such that the outer zone aluminum alloy 110 completely surrounds the inner zone aluminum alloy 120. The flow of molten aluminum alloy 105 may optionally be stopped while the flow of molten aluminum alloy 115 continues. Alternatively, the flow of molten aluminum alloy 115 may optionally be stopped while the flow of molten aluminum alloy 105 continues, or the flow of molten aluminum alloy 105 and 115 may optionally be stopped simultaneously.

The molten aluminum alloys 105 and 115 (and thus the outer zone aluminum alloy 110 and the inner zone aluminum alloy 120) may be different aluminum alloys. For example, the molten aluminum alloy 115/inner zone aluminum alloy 120 may correspond to an alloy that becomes brittle upon cooling to a temperature of greater than or about 200 ℃ or greater than or about 300 ℃.

In some embodiments, the aluminum alloy 115/inner zone aluminum alloy 120 may correspond to a Gao Rongzhi alloy, such as exhibiting a solute concentration of between about 6% and about 18% by weight. For example, the aluminum alloy 115/inner zone aluminum alloy 120 may have a solute concentration of about 6%, about 6.5%, about 7%, about 7.5%, about 8%, about 8.5%, about 9%, about 9.5%, about 10%, about 10.5%, about 11%, about 11.5%, about 12%, about 12.5%, about 13%, about 13.5%, about 14%, about 14.5%, about 15%, about 15.5%, about 16%, about 16.5%, about 17%, about 17.5%, or about 18% by weight. Optionally, the molten aluminum alloy 115/aluminum alloy 120 may correspond to an aluminum alloy having a high copper composition or a high magnesium composition or a high zinc composition, such as in certain 2xxx series aluminum alloys, certain 5xxx series aluminum alloys, and certain 7xxx series aluminum alloys.

As discussed, the molten aluminum alloy 105/outer zone aluminum alloy 110 may correspond to a different alloy than the molten aluminum alloy 115/inner zone aluminum alloy 120. For example, the outer zone aluminum alloy 110 may optionally be more ductile than the inner zone aluminum alloy 120. The interaction of the molten aluminum alloy 105 with the molten aluminum alloy 115 provides a composition gradient zone 125 formed between the outer zone aluminum alloy 110 and the inner zone aluminum alloy 120, as shown in fig. 4. In this way, in an embodiment, at least one of the molten aluminum alloy 105/outer zone aluminum alloy 110 and the composition gradient zone 125 may act as a buffer layer between the molten aluminum alloy 115/inner zone aluminum alloy 120 and the cooling water 130 during casting. For example, due to the greater ductility, the molten aluminum alloy 105/outer zone aluminum alloy 110 may not experience spontaneous cracking or edge cracking when exposed to the cooling water 130, or may not experience cold cracking during casting. On the other hand, spontaneous cracking or edge cracking may occur if the molten aluminum alloy 115/inner zone aluminum alloy 120 is directly exposed to the cooling water 130, or cold cracking may occur during casting, and thus the composition gradient zone 125 and inner zone aluminum alloy 120 may act as a protective layer, for example.

In some embodiments, the molten aluminum alloy 105/outer zone aluminum alloy 110 can have a heat transfer coefficient between about 100W/m.K and about 250W/m.K, such as about 105W/m.K, about 110W/m.K, about 115W/m.K, about 120W/m.K, about 125W/m.K, about 130W/m.K, about 135W/m.K, about 140W/m.K, about 145W/m.K, about 150W/m.K, about 155W/m.K, about 160W/m.K, about 165W/m.K, about 170W/m.K, about 175W/m.K, about 180W/m.K, about 185W/m.K, about 190W/m.K, about 195W/m.K, about 200W/m.K, about 205W/m.K, about 210W/m.K, about 215W/m.K, about 220W/m.K, about 225W/m.K, about 230W/m.K, about 240W/m.K.

Referring to fig. 4, the aluminum alloy 110 representing the outer region may have a thickness corresponding to between 5% and 15% of the total thickness of the ingot. For example, the thickness of the aluminum alloy 110 may be about 5%, about 5.5%, about 6%, about 6.5%, about 7%, about 7.5%, about 8%, about 8.5%, about 9%, about 9.5%, about 10%, about 10.5%, about 11%, about 11.5%, about 12%, about 12.5%, about 13%, about 13.5%, about 14%, about 14.5%, or about 15% of the total thickness of the ingot.

The compositional gradient region 125 may have a thickness corresponding to between 2% and 10% of the total thickness of the ingot. For example, the thickness of the compositional gradient region 125 may be about 2%, about 2.5%, about 3%, about 3.5%, about 4%, about 4.5%, about 6%, about 6.5%, about 7%, about 7.5%, about 8%, about 8.5%, about 9%, about 9.5%, or about 10% of the total thickness of the ingot.

Although the molten aluminum alloy 105/outer zone aluminum alloy 110 is shown in fig. 4 as symmetrical with respect to the molten aluminum alloy 115/inner zone aluminum alloy 120, the depiction of fig. 4 is merely exemplary and other twin casting configurations are possible and are included in the present disclosure, including where each of the molten aluminum alloy 105/aluminum alloy 110 on the left/right sides of the molten aluminum alloy 115/aluminum alloy 120 has a different thickness and/or has a different composition. In some cases, fig. 4 may represent a cylindrical ingot or a rectangular or other shaped ingot, wherein the outer zone aluminum alloy 110 forms a continuous layer around the inner zone aluminum alloy 120, with a composition gradient zone 125 therebetween. Furthermore, the schematic depictions in fig. 1-4 are not to scale.

FIG. 4 provides a schematic illustration of direct chill casting the compositionally graded aluminum alloy product of FIG. 3 as processing continues. As shown in fig. 4, the inner zone aluminum alloy 120 is surrounded by the outer zone aluminum alloy 110, and a composition gradient zone 125 has been formed between the inner zone aluminum alloy 120 and the outer zone aluminum alloy 110. The formation of the composition gradient zone 125 occurs gradually during the casting process, in other words, at any time during the process as shown in fig. 1-4. The compositionally graded aluminum alloys manufactured according to fig. 1-4 may produce composite ingots exhibiting limited amounts of various types of cracking, such as cold cracking. The compositionally graded aluminum alloys manufactured according to fig. 1-4 may produce composite ingots exhibiting a limited amount of porous structure that may be used as nucleation sites for fracture during hot rolling.

In some examples, the molten metal used in the methods described herein includes an aluminum alloy, e.g., a first aluminum alloy for the inner region and a second aluminum alloy for the outer region, wherein the first aluminum alloy and the second aluminum alloy are different. Each of the first aluminum alloy and the second aluminum alloy may be selected from a 1Xxx series aluminum alloy, a 2Xxx series aluminum alloy, a 3Xxx series aluminum alloy, a 4Xxx series aluminum alloy, a 5Xxx series aluminum alloy, a 6Xxx series aluminum alloy, a 7Xxx series aluminum alloy, or an 8Xxx series aluminum alloy.

As non-limiting examples, exemplary 1 xxx-series aluminum alloys for use in the methods described herein may include AA1100, AA1100A, AA1200, AA1200A, AA1300, AA11 10, AA1120, AA1230A, AA1235, AA1435, AA1145, AA1345, AA1445, AA1150, AA1350A, AA1450, AA1370, AA1275, AA1185, AA1285, AA1385, AA1188, AA1190, AA1290, AA1193, AA1 198, or AA1 199. Examples may also include P1020 aluminum alloy or P0406 aluminum alloy.

Non-limiting exemplary 2xxx series aluminum alloys for use in the methods described herein may include AA2001, a2002, AA2004, AA2005, AA2006, AA2007A, AA2007B, AA2008, AA2009, AA2010, AA2011A, AA2111, AA211 1A, AA211 1B, AA2012, AA2013, AA2007A, AA2007B, AA; AA2014, AA2014A, AA2214, AA2015, AA2016, AA2017A, AA2117, AA2018, AA2218, AA2618A, AA2219, AA2319, AA2419, AA2519, AA2021, AA2022, AA2023, AA2024A, AA2124, AA2224A, AA2324, AA2021, AA2022, AA2023, AA2024A, AA2124 AA2424, AA2524, AA2624, AA2724, AA2824, AA2025, AA2026, AA2027, AA2028A, AA2028B, AA, 2028C, AA2029, AA2030, AA2031, AA2032, AA2034, AA2036, AA2037, AA2038, AA2039, AA2139, AA2040, AA2041, AA2044, AA2045, AA2050, AA2055, AA2056, AA2060, AA2065, AA2070, AA2076, AA2090, AA2091, AA2094, AA2095, AA2195, AA2196, AA2097, AA2197, AA2397, AA2198, AA2099 or AA2199.

Non-limiting exemplary 3xxx series aluminum alloys for use in the methods described herein may include AA3002, AA3102, AA3003, AA3103A, AA3103B, AA3203, AA3403, AA3004A, AA3104, AA3204, AA3304, AA3005A, AA3105, AA3105A, AA3105B, AA3007, AA3107, AA3207A, AA3307, AA3009, AA3010, AA3110, AA3011, AA3012, AA A, AA3013, AA3014, AA3015, AA3016, AA3017, AA3019, AA3020, AA3021, AA3025, AA3026, AA3030, AA3130, or AA3065.

Non-limiting exemplary 4xxx series aluminum alloys for use in the methods described herein may include AA4004, AA4104, AA4006, AA4007, AA4008, AA4009, AA4010, AA4013, AA4014, AA4015A, AA4115, AA4016, AA4017, AA4018, AA4019, AA4020, AA4021, AA4026, AA4032, AA4043A, AA4143, AA4343, AA4643, AA4943, AA4044, AA4045, AA4145A, AA4046, AA4047A, or AA4147.

Non-limiting exemplary 5xxx series aluminum alloys for use in the methods described herein may include AA5182, AA5183, AA5005A, AA5205, AA5305, AA5505, AA5006, AA5106, AA5010, AA5110A, AA5210, AA5310, AA5016, AA5017, AA5018A, AA5019, AA5019A, AA5119, AA5119A, AA5021, AA5022, AA5023, AA5024, AA5026, AA5027, AA5028, AA5040, AA5140, AA5041, AA5042, AA5043, AA5049, AA5149, AA5249, AA5349, AA5449A, AA5050, AA5050A, AA5050, AA5051 AA5051A, AA5151, AA5251A, AA5351, AA5451, AA5052, AA5252, AA5352, AA5154, A, AA, 5154, C, AA, 5254, AA5354, AA5454, AA5554, AA5654, A, AA5754, AA5854, AA5954, AA5056, AA5356A, AA5456, AA5456A, AA 54B, AA5556 AA5556A, AA5556B, AA5556C, AA5257, AA5457, AA5557, AA5657, AA5058, AA5059, AA5070, AA5180A, AA5082, AA5182, AA5083, AA5183A, AA5283, AA5283A, AA5283B, AA5383, AA5483, AA5086, AA5186, AA5087, AA5187, or AA5088.

Non-limiting exemplary 6 xxx-series aluminum alloys for use in the methods described herein may include AA6101, AA6101A, AA6101B, AA6201, AA6201A, AA6401, AA6501, AA6002, AA6003, AA6103, AA6005A, AA6005B, AA6005C, AA6105, AA6205, AA6006, AA6106, AA6206, AA6008, AA6009, AA6010, AA6110, AA 61A, AA6011, AA6012A, AA6013, AA6113, AA6014, AA6015, AA6016, AA6018, AA6019, AA6025, AA6026, AA6021, AA6022, AA6023, AA6024, AA6025, AA 6012; AA6027, AA6028, AA6031, AA6032, AA6033, AA6040, AA6041, AA6042, AA6043, AA6151, AA6351A, AA6451, AA6951, AA6053, AA6055, AA6056, AA6156, AA6060, AA6160, AA6260, AA6360, AA6460B, AA6560, AA6660, AA6061 396261, AA6361, AA6162, AA6262A, AA6063, AA6063A, AA6463, AA6463A, AA6763, a6963, AA6064, AA 60A, AA6065, AA6066, AA6068, AA6069, AA6070, AA6081, AA6181, AA A, AA6082, AA6082A, AA6182, AA6091 or AA6092.

Non-limiting exemplary 7 xxx-series aluminum alloys for use in the methods described herein may include AA7011, AA7019, AA7020, AA7021, AA7039, AA7072, AA7075, AA7085, AA7108A, AA7015, AA7017, AA7018, AA7019A, AA7024, AA7025, AA7028, AA7030, AA7031, AA7033, AA7035A, AA7046, AA7046A, AA7003, AA7004, AA7005, AA7009, AA7010, AA7011, AA7012, AA7014, AA7016, AA7116, AA7122, AA7023, AA 7026; AA7029, AA7129, AA7229, AA7032, AA7033, AA7034, AA7036, AA7136, AA7037, AA7040, AA7140, AA7041, AA7049A, AA7149, AA7204, AA7249, AA7349, AA7449, AA7050A, AA7150, AA7250, AA7055, AA7155, AA7255, AA7056, AA7060, AA7064, AA7065, AA7068, AA7168, AA7175, AA7475, AA7076, AA7178, AA7278, AA7181, AA7185, AA7090, AA7093, 7095, or AA7099.

Non-limiting exemplary 8xxx series aluminum alloys for use in the methods described herein may include AA8005, AA8006, AA8007, AA8008, AA8010, AA8011A, AA8111, AA8211, AA8112, AA8014, AA8015, AA8016, AA8017, AA8018, AA8019, AA8021A, AA8021B, AA8022, AA8023, AA8024, AA8025, AA8026, AA8030, AA8130, AA8040, AA8050, AA8150, AA8076A, AA, AA8077, AA8177, AA8079, AA8090, AA8091, or AA8093.

In some examples, referring again to fig. 4, the first aluminum alloy that may be used for the inner zone aluminum alloy 120 includes a 7xxx series aluminum alloy, a 5xxx series aluminum alloy, or a 2xxx series aluminum alloy. In some specific examples, the first or inner region aluminum alloy 120 can include 7075 aluminum alloy, 5182 aluminum alloy, or 2024 aluminum alloy. In some examples, the second aluminum alloy that may be used for the outer region aluminum alloy 110 includes a 1xxx series aluminum alloy. The second or outer region aluminum alloy 110 may optionally include a 1xxx series aluminum alloy having a purity of at least 99.7%. In some specific examples, the second or outer region aluminum alloy 110 may include a P1020 aluminum alloy or a P0406 aluminum alloy.

Fig. 5A provides a cross-sectional view illustrating a compositionally graded aluminum alloy product 200 made in accordance with fig. 1-4. The outer region 210 encloses the inner region 220, and a composition gradient region 225 is disposed between the outer region 210 and the inner region 220. Region a of fig. 5A is shown in more detail in fig. 5B. At least one alloying element of the first aluminum alloy as in the inner zone 220 has a decreasing content through the composition gradient zone 225 in the direction D from the inner zone 220 to the outer zone 210. In other words, the content of alloying element E is higher in the inner region 220 and decreases throughout the thickness of the compositional gradient region 225, as schematically shown in fig. 5B. The outer region 210 may be free or substantially free of element E, as schematically illustrated in fig. 5B. Substantially no element E is included in an amount less than about 0.1wt.%. In some embodiments, at least one alloying element E of the first aluminum alloy as in the inner region 220 of fig. 5B comprises Zn, cu, mg, or Na.

Fig. 6 provides a perspective schematic view of a compositionally graded aluminum alloy product such as manufactured in accordance with fig. 1-4. The ingot may have a flat end or a full radius end. The ingot is shown with the head of the ingot (or top as in fig. 6) cut. The product may be an ingot 600 having an inner region 620 comprising a first aluminum alloy and an outer region 610 surrounding the inner region 620. The outer region 610 comprises a second aluminum alloy that is different from the first aluminum alloy of the inner region 620. A composition gradient region 625 is disposed between the inner region 620 and the outer region 610. In some cases, at least one alloying element of the first aluminum alloy has a decreasing content throughout the composition gradient zone 625 in a direction from the inner zone 620 to the outer zone 610. In another embodiment, stripping or other mechanical removal techniques may optionally be used to remove at least a portion of the tail of the ingot after casting (as opposed to the head or top removed as shown in fig. 6). Because cemented carbide ingots are prone to cracking at the ingot tail end during or after casting, a compositionally graded aluminum alloy product may be used at the tail end to minimize or reduce the effects of tail cracking.

Peeling or other mechanical removal techniques may optionally be used to remove at least a portion of the composition gradient zone and the outer region from the ingot. Fig. 7A and 7B provide schematic illustrations of stripping a compositionally graded aluminum alloy product, such as a composite ingot 700. At least one surface 740 (which may be a rolled surface as shown) is peeled to remove material using a peeling apparatus or tool 750 as shown in fig. 7A. The rolling surface may be the widest surface. As shown, surface 740 includes a composition gradient region 725 and an outer region 710. At least one surface 740 is peeled to remove material using another peeling apparatus or tool 750 as shown in fig. 7B. As shown, the removed surface 740 includes a composition gradient region 725 and an outer region 710. The tool 750 of FIG. 7A is depicted as a band saw type device. In fig. 7B, tool 750 is depicted as a mill-type device, wherein a rotary cutting tool is used to cut and remove composition gradient zone 725 and/or outer zone 710, such as using one or more milling operations/passes. In some configurations, multiple machining tools may be used simultaneously and/or sequentially to remove the outer regions and/or the compositional gradient regions, such as when the composite ingot 700 is oriented in a configuration in which the outer regions and/or compositional gradient region layers are arranged vertically, rather than in the horizontal configuration depicted in fig. 7A and 7B. In some embodiments, at least a portion of the composition gradient zone and the outer zone may optionally be removed from multiple sides of the ingot (head side, tail side, and edges of the ingot) using peeling or other mechanical removal techniques to reduce hot rolling effects, such as cracking that typically occurs during hot rolling. The composition gradient zone may also be used on multiple sides at the outer zone to reduce the effects of thermal cracking. Thermal cracking is formed due to the long solidification range of the alloy and may start from the mushy zone of the molten pool. Typically in the case of DC slabs, cold cracking begins during casting and propagates as thermal cracking. Thus, solidifying purer alloy material at the outer region may be useful to reduce thermal cracking failure.

Referring to fig. 8A, the ingot is shown with the head (or top) of the ingot cut. Fig. 8A and 8B provide schematic illustrations of a compositionally graded aluminum alloy product or ingot 800 before and after the side is peeled to produce a monolithic ingot 850. The aluminum alloy product or ingot 800 of fig. 8A includes an inner region 820, a composition gradient region 825, and an outer region 810 prior to peeling. To form a monolithic ingot 850 comprising, consisting of, or consisting essentially of an inner region (e.g., a first aluminum alloy) as depicted in fig. 8B, a process such as a peeling or other machining process that removes the outer region 810 (or second aluminum alloy) and the composition gradient region 825 from the composite ingot 800 may be used. In the example of fig. 8A-8B, an aluminum alloy product or ingot 800 is peeled on each longitudinal surface (and on the ends as needed) to produce a monolithic ingot 850 as in fig. 8B, wherein the monolithic ingot 850 includes the inner region 820 of fig. 8A. In some embodiments, monolithic ingot 850 comprises only the first aluminum alloy of inner region 820. In some embodiments, portions of the compositionally graded region 825 may remain on the outer surface.

Fig. 9 provides a schematic illustration of a compositionally graded aluminum alloy product or composite ingot 900 in which an outer region 910 and a compositionally graded region 925 are peeled to produce a monolithic ingot 920 of a first aluminum alloy, which is then further processed by at least one rolling process to produce the aluminum alloy product. Different stripping techniques may be used depending on the casting configuration and thickness, length, width, and composition of the outer region 910 and the composition gradient region 925 of the second aluminum alloy of the composite ingot 900. In fig. 9, the peeling of the composite ingot 900 involves a machining process wherein the composite ingot 900 is moved relative to a machining tool 950 to remove all or a portion of the outer region 910 comprising the second aluminum alloy and optionally the composition gradient zone 925 as an at least partially continuous layer.

Other components may be useful or desirable to remove the outer region 910 and the compositional gradient region 925 using the configuration depicted in fig. 9, such as lubrication/cooling fluids, debris collection mechanisms, etc., but these are not shown in the figures to avoid obscuring other details. Other machining techniques and operations beyond those shown are also possible. For example, to machine some ingots, such as cylindrical ingots (not shown), a lathe or other device in which the ingot is rotated while the lathe is held stationary may be used.

The material properties may determine useful peeling techniques because some aluminum alloys may be more suitable for processing using a particular technique than others. Alternatively, available stripping equipment may be used to determine which aluminum alloys are available for the outer zone and the composition gradient zone.

However, in some cases, a combination of material properties of aluminum alloys for the outer and inner regions may be evaluated to identify which aluminum alloy is suitable for the outer region. For example, the heat transfer coefficient of the outer zone may be a useful property to consider, as it may be desirable to control the heat transfer rate from the inner zone to the outer zone and cooling water to prevent breakage and/or damage of the inner zone during casting. The ductility of the outer zone may also play a role in selecting an appropriate outer zone aluminum alloy, as it may be beneficial to select an outer zone having a particular ductility to accommodate stresses that may develop within the inner zone to provide a protective effect against cracking, crazing, or other damage of the inner zone during the casting process. The thermal expansion characteristics may also play a role in selecting an appropriate alloy for the outer region, as it may be beneficial to use an alloy in the outer region that has the same or different thermal expansion characteristics as the alloy of the inner region to accommodate thermal contraction of the inner region and provide a protective effect against cracking, crazing or other damage of the inner region during cooling that occurs during or after casting.

In some cases, the composite ingot may be stable during casting, but may fracture prior to or during stripping due to residual stresses within the composite ingot. Optionally, the composite ingot may be subjected to various processing steps after casting and prior to skinning to relieve, limit, or otherwise reduce stresses within the composite ingot. For example, the composite ingot may optionally be preheated and/or homogenized after removal from the casting pit and prior to skinning. Exemplary preheat and homogenization temperatures may be in the range of about 325 ℃ to about 520 ℃, such as, for example, about 325 ℃ to about 450 ℃ or about 325 ℃ to about 400 ℃. In some embodiments, the ingot is maintained at a temperature or temperatures for a holding time of 2 to 24 hours for homogenization, and then the ingot is cooled. Preheating and/or homogenizing the composite ingot to temperatures and times within these ranges can be used to limit intermetallic precipitation.

Once prepared, the monolithic ingot may be processed by any suitable means, such as ingot 920 shown in fig. 9. Fig. 9 also provides a schematic illustration of subjecting a monolithic ingot 920 prepared with a skinning apparatus or tool 950 according to a composite ingot casting and skinning process 955 to additional non-limiting processing steps including a homogenization step 960, a hot rolling step 965, and a cold rolling step 970. Other example processing steps include, but are not limited to, a solution heat treatment step, a pre-heating step between the homogenization step 960 and the hot rolling step 965, and a pre-aging step. In some cases, the peeling process 955 may optionally be the process described in fig. 7A-7B.

In the homogenization step 960, the product, such as a monolithic ingot 920, is heated to a temperature in the range of about 400 ℃ to about 500 ℃. For example, the product may be heated to a temperature of about 400 ℃, about 410 ℃, about 420 ℃, about 430 ℃, about 440 ℃, about 450 ℃, about 460 ℃, about 470 ℃, about 480 ℃, about 490 ℃, or about 500 ℃. The product is then allowed to soak (i.e., remain at the indicated temperature) for a period of time to produce a homogenized product. In some examples, the total time of the homogenization step 960 (including the heating and soaking phases) may be up to 24 hours. For example, for the homogenization step 960, the product may be heated from 400 ℃ to about 520 ℃ and soaked for a total time of up to 24 hours. Optionally, for the homogenization step 960, the product may be heated to below 490 ℃ and soaked for a total time of up to 18 hours. In some cases, the homogenization step 960 includes a number of processes. In some non-limiting examples, the homogenizing step 960 includes heating the product to a first temperature for a first period of time and then to a second temperature for a second period of time. In one non-limiting example, the product may be heated to about 465 ℃ for about 3.5 hours, and then heated to about 480 ℃ for about 6 hours.

After the homogenization step 960, a hot rolling step 965 may be performed. The homogenized product may be allowed to cool to a temperature between 300 ℃ and 520 ℃ before hot rolling begins. For example, the homogenized product may be allowed to cool to a temperature between 325 ℃ to 500 ℃ or from 350 ℃ to 450 ℃ or from 375 ℃ to 425 ℃. The homogenized product may then be hot rolled at a temperature between 300 ℃ and 520 ℃ to form hot rolled plates, hot rolled saute plates, or hot rolled sheets having a gauge between 3mm and 200mm (e.g., 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm, 95mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm, 200mm, or any value therebetween). During hot rolling, the temperature and other operating parameters may be controlled such that the temperature of the hot rolled intermediate product when exiting the hot rolling mill is no more than 440 ℃, no more than 430 ℃, no more than 420 ℃, no more than 410 ℃, or no more than 400 ℃.

As shown, the hot rolled product may be subjected to a cold rolling step 970 that uses a cold rolling mill to process the hot rolled product into a thinner product, such as a cold rolled sheet or a sauter plate. In some cases, the cold rolled product may have a gauge of between about 0.5mm to 10mm, for example between about 0.7mm to 6.5 mm. Optionally, the cold rolled product may have a gauge of 0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm, 3.5mm, 4.0mm, 4.5mm, 5.0mm, 5.5mm, 6.0mm, 6.5mm, 7.0mm, 7.5mm, 8.0mm, 8.5mm, 9.0mm, 9.5mm, or 10.0 mm. Cold rolling may be performed to obtain a final gauge thickness representing a gauge reduction of at most 85% (e.g., a reduction of at most 10%, at most 20%, at most 30%, at most 40%, at most 50%, at most 60%, at most 70%, at most 80%, or at most 85%) as compared to the gauge prior to the start of cold rolling.

Optionally, an intermediate annealing step may be performed during the cold rolling step, such as wherein a first cold rolling process is performed, followed by an annealing process (intermediate annealing), followed by a second cold rolling process. The intermediate annealing step may be performed at a temperature of about 300 ℃ to about 450 ℃ (e.g., about 310 ℃, about 320 ℃, about 330 ℃, about 340 ℃, about 350 ℃, about 360 ℃, about 370 ℃, about 380 ℃, about 390 ℃, about 400 ℃, about 410 ℃, about 420 ℃, about 430 ℃, about 440 ℃, or about 450 ℃). In some cases, the intermediate annealing step includes multiple processes. In some non-limiting examples, the intermediate annealing step may include heating the partially cold rolled product to a first temperature for a first period of time, followed by heating to a second temperature for a second period of time. For example, the partially cold rolled product may be heated to about 410 ℃ for about 1 hour, and then heated to about 330 ℃ for about 2 hours.

The green monolithic aluminum alloy ingot, homogenized monolithic aluminum alloy ingot, or rolled monolithic aluminum alloy product may optionally be subjected to a solution heat treatment step. The dissolution heat treatment step may be any suitable treatment that results in solutionizing of the soluble particles. The product may optionally be heated to a Peak Metal Temperature (PMT) of up to 590 ℃ (e.g., from 400 ℃ to 590 ℃) and soaked under PMT for a period of time to form a hot product. For example, the cast, homogenized, or rolled product may be soaked at 480 ℃ for a soaking time of up to 30 minutes (e.g., 0 seconds, 60 seconds, 75 seconds, 90 seconds, 5 minutes, 10 minutes, 20 minutes, 25 minutes, or 30 minutes). After heating and soaking, the hot product is optionally rapidly cooled at a rate of greater than 200 ℃/s to a temperature between 500 ℃ and 200 ℃ to produce a heat treated product. In one example, the hot product is cooled to a temperature between 450 ℃ and 200 ℃ at a quench rate of greater than 200 ℃/sec. Optionally, in other cases, the cooling rate may be faster.

Optionally, for example, the heat treated product may be subjected to a pre-ageing treatment by reheating prior to winding. The pre-ageing treatment may be carried out at a temperature of from about 70 ℃ to about 125 ℃ for a period of up to about 6 hours. For example, the pre-ageing treatment may be performed at a temperature of about 70 ℃, about 75 ℃, about 80 ℃, about 85 ℃, about 90 ℃, about 95 ℃, about 100 ℃, about 105 ℃, about 110 ℃, about 115 ℃, about 120 ℃, or about 125 ℃. Optionally, a pre-ageing treatment may be performed for about 30 minutes, about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 5 hours, or about 6 hours. The pre-ageing treatment may be performed by passing the heat treated product through heating means, such as means emitting radiant heat, convective heat, inductive heat, infrared heat, etc.

The monolithic aluminum alloy products described herein can be used to make products in the form of sheets, plates, or other suitable products. For example, a plate comprising the product described herein may be prepared by processing a monolithic aluminum alloy ingot in a homogenization step followed by a hot rolling step. In the hot rolling step, the monolithic aluminum alloy product may be hot rolled to a gauge of 200mm thickness or less (e.g., from about 10mm to about 200 mm). For example, a monolithic aluminum alloy product can be hot rolled into a plate having a final gauge thickness of about 10mm to about 175mm, about 15mm to about 150mm, about 20mm to about 125mm, about 25mm to about 100mm, about 30mm to about 75mm, or about 35mm to about 50 mm. In some cases, the plate may be rolled into a thinner metal product, such as a sheet. In some embodiments, the final sheet may be hot stamped and/or thermoformed, and optionally anodized.

Referring to fig. 10A, the ingot is shown with the head and tail of the ingot cut. Fig. 10A and 10B provide schematic diagrams of a composition gradient aluminum alloy product that has been partially peeled, the configuration in fig. 10A being peeled at the first and second edges, and the configuration in fig. 10B being peeled on the upper and lower rolling surfaces. In the embodiment where the first and second edges (end surfaces) are peeled as shown in fig. 10A, the corrosion resistance and bonding durability of the sheet can be improved by having a purer and thus softer outer zone alloy on the rolled surface as compared to a product consisting of only the inner zone alloy. Thus, a sheet exhibiting improved surface properties can be obtained without additional treatment, and in some cases, bending, punching, scribing, and brushing can be improved. In the embodiment where the upper and lower rolling surfaces are stripped as shown in fig. 10B, the outer zone alloy at the ingot end may reduce edge cracking that typically occurs due to hot rolling for inner zone alloys that are prone to edge cracking during hot rolling. Thus, after hot rolling, these edges can be trimmed as needed. Additionally, softer (purer) outer zone alloys may result in reduced cracking effects at the edges.

The freshly peeled products 1000A and 1000B of fig. 10A and 10B, respectively, may be processed similarly as described above with respect to ingot 920 of fig. 9, including but not limited to homogenization step 1060, hot rolling step 1065, and cold rolling step 1070. Other example processing steps include, but are not limited to, a solution heat treatment step, a pre-heating step between homogenization step 1060 and hot rolling step 1065, and a pre-aging step.

Fig. 11 provides a schematic illustration of a not yet skinned compositionally graded aluminum alloy product 1100 and the fabrication and processing of ingots to fabricate an aluminum alloy product. Alloy product 1100, similar to ingot 600 as shown in fig. 6, may be processed similarly as described above, such as including, but not limited to, homogenization step 1160, hot rolling step 1165, and cold rolling step 1170. Similar to the freshly peeled products 1000A and 1000B of FIGS. 10A and 10B, other example processing steps include, but are not limited to, a solution heat treatment step, a pre-heating step between the homogenization step 1160 and the hot rolling step 1165, and a pre-aging step.

The following examples will serve to further illustrate the 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 present invention. During the study described in the examples below, conventional procedures were followed unless otherwise indicated. Some of the procedures are described below for illustrative purposes.

Example 1

The composite ingot is formed by a simultaneous twin casting technique, such as that shown in fig. 1-4. The aluminum alloy used for the inner zone was AA5182 aluminum alloy. The aluminum alloy used for the outer zone is AA1100 aluminum alloy. The AA1100 product was diluted into AA5182 at the compositional gradient zone. This allows for direct waste recovery and recycling, as no segregation or toxicity of the stream is required. The gradient liquid layers formed by molten AA5182 and molten AA1100 are similar to those in layered forms of thermocline (heat), salt-skip (salinity) or chemical-skip (chemical) which are readily found in nature. In order to maintain a region of compositional gradient at the interface of the two molten alloys, turbulence is reduced by a method in which structures are used to redirect the casting speed vector and thus eliminate mixing. In this example, molten aluminum casting using a combination of bags or mesh screens is used to achieve a limited amount of turbulence such that the flow of molten metal is redirected perpendicular to the casting direction. The thickness of the as-cast compositional gradient region may be about 10.5mm per side and the thickness of the outer region may be about 26mm per side. During the peeling operation, approximately 36.5mm of each side corresponding to the outer region may be removed from each rolling surface by a separate milling operation to form a monolithic AA5182 aluminum ingot. The single ingot is transferred to a rolling mill for subsequent processing. Edge cracking of the short sides of the ingot can be suppressed.

Example 2

Another composite ingot is formed by a simultaneous twin casting technique, such as shown in fig. 1-4, in which two alloys are poured into a single mold. The aluminum alloy used for the inner zone is AA7075 aluminum alloy. The aluminum alloy used for the outer zone is AA1100 aluminum alloy. The AA 1100-series products were diluted in AA7075 in the composition gradient zone. This allows for direct waste recovery and recycling, as no segregation or toxicity of the stream is required. The gradient liquid layers formed by molten AA7075 and molten AA1100 are similar to those in layered forms of thermocline (heat), salt-skip (salinity) or chemical-skip (chemical) which are readily found in nature. In order to maintain a region of compositional gradient at the interface of the two molten alloys, turbulence is reduced by a method in which structures are used to redirect the casting speed vector and thus eliminate mixing. The combination bag or mesh screen is used to achieve a limited amount of turbulence such that the flow of molten metal is redirected perpendicular to the casting direction, for example parallel to the desired interface plane. By controlling the flow rate, turbulence is minimized. Alternatively, a magnetic field may be used to suppress turbulence in a direction perpendicular to the composition gradient zone. The thickness of the as-cast compositional gradient region is about 10.5mm per side, and the thickness of the outer region may be about 26mm per side. And transferring the steel ingot to a rolling mill for subsequent processing. Cold cracking during casting of the ingot will be inhibited.

Illustrative aspects

As used below, any reference to a series of aspects (e.g., "aspects 1-4") or a set of non-enumerated aspects (e.g., "any preceding or subsequent aspect") should be construed separately to refer to each of those aspects (e.g., "aspects 1-4" should be construed to be "aspects 1, 2, 3, or 4").

Aspect 1 is a method of making a compositionally graded aluminum alloy product, the method comprising: casting a composite ingot in a mold, the composite ingot comprising: an inner region comprising a first aluminum alloy; an outer region surrounding the inner region, the outer region comprising a second aluminum alloy different from the first aluminum alloy; and a composition gradient zone between the inner zone and the outer zone, wherein at least one alloying element of the first aluminum alloy has a content that decreases throughout the composition gradient zone in a direction from the inner zone to the outer zone.

Aspect 2 is the method of any preceding or subsequent aspect, wherein the first aluminum alloy and the second aluminum alloy are cast simultaneously.

Aspect 3 is the method of any preceding or subsequent aspect, wherein the first aluminum alloy is delivered to the mold from a first elevation, and the second aluminum alloy is delivered to the mold from a second elevation, wherein the second elevation is different from the first elevation.

Aspect 4 is the method of any preceding or subsequent aspect, further comprising peeling the composite ingot to remove at least a portion of the composition gradient zone and the outer zone from a rolling surface.

Aspect 5 is the method of any preceding or subsequent aspect, wherein peeling comprises removing material to produce a monolithic ingot comprising the first aluminum alloy.

Aspect 6 is the method of any preceding or subsequent aspect, wherein the first aluminum alloy comprises a 7xxx series aluminum alloy, a 5xxx series aluminum alloy, or a 2xxx series aluminum alloy.

Aspect 7 is the method of any preceding or subsequent aspect, wherein the first aluminum alloy comprises 7075 aluminum alloy, 5182 aluminum alloy, or 2024 aluminum alloy.

Aspect 8 is the method of any preceding or subsequent aspect, wherein the second aluminum alloy comprises a 1xxx series aluminum alloy.

Aspect 9 is the method of any preceding or subsequent aspect, wherein the second aluminum alloy has a purity of at least 99.7%.

Aspect 10 is the method of any preceding or subsequent aspect, wherein the at least one alloying element of the first aluminum alloy comprises Zn, cu, mg, or Na.

Aspect 11 is the method of any preceding or subsequent aspect, wherein the outer region is substantially free of the at least one alloying element.

Aspect 12 is the method of any preceding or subsequent aspect, wherein the composite ingot is substantially free of cracking.

Aspect 13 is the method of any preceding or subsequent aspect, wherein the cracking comprises cold cracking, thermal cracking, edge cracking, or tail cracking.

Aspect 14 is the method of any preceding or subsequent aspect, wherein the composite ingot is substantially free of porous structure.

Aspect 15 is the method of any preceding or subsequent aspect, wherein the porous structure comprises pores that are nucleation sites from fracture during hot rolling.

Aspect 16 is the method of any preceding or subsequent aspect, wherein casting the composite ingot comprises a direct chill casting process, wherein the inner region and the outer region are co-cast in an arrangement in which the outer region is in contact with cooling water.

Aspect 17 is the method of any preceding or subsequent aspect, wherein the outer region has a thickness of 7% to 15% of a total thickness of the composite ingot.

Aspect 18 is the method of any preceding or subsequent aspect, wherein the compositional gradient region has a thickness of 2% to 10% of a total thickness of the composite ingot.

Aspect 19 is the method of any preceding or subsequent aspect, further comprising processing the monolithic ingot or the composite ingot to form an aluminum alloy sauter plate, or sheet comprising the first aluminum alloy.

Aspect 20 is the method of any preceding or subsequent aspect, further comprising one or more of a homogenization process, a hot rolling process, a cold rolling process, an annealing process, a solution heat treatment process, a quenching process, or a surface treatment process.

Aspect 21 is the method of any preceding or subsequent aspect, further comprising directing a magnetic field during casting, the magnetic field configured to inhibit turbulence in a direction perpendicular to the composition gradient zone.

Aspect 22 is the method of any preceding or subsequent aspect, further comprising directing a magnetic field during casting to inhibit turbulence in a direction perpendicular to the compositional gradient region, wherein directing comprises positioning the magnetic field at a height between the first height and the second height.

Aspect 23 is the method of any preceding or subsequent aspect, the method comprising directing a magnetic field during casting to inhibit turbulence in a direction perpendicular to the compositional gradient region, wherein directing the magnetic field comprises providing a slag dam positioned at a height within the melt body between the first height and the second height.

Aspect 24 is an aluminum alloy composite ingot produced by the method of any one of the preceding or subsequent aspects.

Aspect 25 is an aluminum alloy composite ingot, comprising: an inner region comprising a first aluminum alloy; an outer region surrounding the inner region, the outer region comprising a second aluminum alloy different from the first aluminum alloy; and a composition gradient zone between the inner zone and the outer zone, wherein at least one alloying element of the first aluminum alloy has a content that decreases throughout the composition gradient zone in a direction from the inner zone to the outer zone.

Aspect 26 is the aluminum alloy composite ingot of any preceding or subsequent aspect, wherein the first aluminum alloy comprises a 7xxx series aluminum alloy, a 5xxx series aluminum alloy, or a 2xxx series aluminum alloy.

Aspect 27 is the aluminum alloy composite ingot of any preceding or subsequent aspect, wherein the first aluminum alloy comprises 7075 aluminum alloy, 5182 aluminum alloy, or 2024 aluminum alloy.

Aspect 28 is the aluminum alloy composite ingot of any preceding or subsequent aspect, wherein the second aluminum alloy comprises a 1xxx series aluminum alloy.

Aspect 29 is the aluminum alloy composite ingot of any preceding or subsequent aspect, wherein the second aluminum alloy has a purity of at least 99.7%.

Aspect 30 is the aluminum alloy composite ingot of any preceding or subsequent aspect, wherein the at least one alloying element of the first aluminum alloy comprises Zn, cu, mg, or Na.

Aspect 31 is the aluminum alloy composite ingot of any preceding or subsequent aspect, wherein the outer region is substantially free of the at least one alloying element.

Aspect 32 is the aluminum alloy composite ingot of any preceding or subsequent aspect, wherein the composite ingot is substantially free of cracking.

Aspect 33 is the aluminum alloy composite ingot of any preceding or subsequent aspect, wherein the cracking comprises cold cracking, thermal cracking, edge cracking, or tail cracking.

Aspect 34 is the aluminum alloy composite ingot of any preceding or subsequent aspect, wherein the composite ingot is substantially free of porous structure.

Aspect 35 is the aluminum alloy composite ingot of any preceding or subsequent aspect, wherein the porous structure comprises pores that are nucleation sites from fracture during hot rolling.

Aspect 36 is the aluminum alloy composite ingot of any preceding or subsequent aspect, wherein the outer region has a thickness of 7% to 15% of a total thickness of the composite ingot.

Aspect 37 is the aluminum alloy composite ingot of any preceding or subsequent aspect, wherein the compositional gradient region has a thickness of 2% to 10% of a total thickness of the composite ingot.

Aspect 38 is a rolled aluminum alloy product formed by the method of any of the preceding or subsequent aspects.

Aspect 39 is a rolled aluminum alloy product, comprising: an inner region comprising a first aluminum alloy; an outer region surrounding the inner region, the outer region comprising a second aluminum alloy different from the first aluminum alloy; and a composition gradient zone between the inner zone and the outer zone, wherein at least one alloying element of the first aluminum alloy has a content that decreases throughout the composition gradient zone in a direction from the inner zone to the outer zone.

Aspect 40 is the rolled aluminum alloy product of any preceding or subsequent aspect, made from the ingot of any preceding or subsequent aspect.

Aspect 41 is the rolled aluminum alloy product of any preceding or subsequent aspect, wherein the first aluminum alloy comprises a 7xxx series aluminum alloy, a 5xxx series aluminum alloy, or a 2xxx series aluminum alloy.

Aspect 42 is the rolled aluminum alloy product of any preceding or subsequent aspect, wherein the first aluminum alloy comprises 7075 aluminum alloy, 5182 aluminum alloy, or 2024 aluminum alloy.

Aspect 43 is the rolled aluminum alloy product of any preceding or subsequent aspect, wherein the second aluminum alloy comprises a 1xxx series aluminum alloy.

Aspect 44 is the rolled aluminum alloy product of any preceding or subsequent aspect, wherein the second aluminum alloy has a purity of at least 99.7%.

Aspect 45 is the rolled aluminum alloy product of any preceding or subsequent aspect, wherein the at least one alloying element of the first aluminum alloy comprises Zn, cu, mg, or Na.

Aspect 46 is the rolled aluminum alloy product of any preceding or subsequent aspect, wherein the outer region is substantially free of the at least one alloying element.

Aspect 47 is the rolled aluminum alloy product of any preceding or subsequent aspect, wherein the composite ingot is substantially free of cracking.

Aspect 48 is the rolled aluminum alloy product of any preceding or subsequent aspect, wherein the cracking comprises cold cracking, thermal cracking, edge cracking, or tail cracking.

Aspect 49 is the rolled aluminum alloy product of any preceding or subsequent aspect, wherein the composite ingot is substantially free of porous structure.

Aspect 50 is the rolled aluminum alloy product of any preceding or subsequent aspect, wherein the porous structure comprises pores that are nucleation sites from fracture during hot rolling.

Aspect 51 is the rolled aluminum alloy product of any preceding or subsequent aspect, wherein the outer region has a thickness of 7% to 15% of a total thickness of the composite ingot.

Aspect 52 is the rolled aluminum alloy product of any preceding or subsequent aspect, wherein the composition gradient zone has a thickness of 2% to 10% of a total thickness of the composite ingot.

All patents, publications, and abstracts cited above are incorporated herein by reference in their entirety. The foregoing description of the embodiments (including the illustrated embodiments) has been presented for purposes of illustration and description only and is not intended to be exhaustive or to be limited to the precise forms disclosed. Many modifications, variations and uses of the embodiments will be apparent to those skilled in the art.

Claims

1. A method of preparing a compositionally graded aluminum alloy product, the method comprising:

casting a composite ingot in a mold, the composite ingot comprising:

an inner region comprising a first aluminum alloy,

an outer region surrounding the inner region, the outer region comprising a second aluminum alloy different from the first aluminum alloy; and

A composition gradient zone between the inner zone and the outer zone, wherein at least one alloying element of the first aluminum alloy has a decreasing content throughout the composition gradient zone in a direction from the inner zone to the outer zone.

2. The method of claim 1, wherein the first aluminum alloy and the second aluminum alloy are cast simultaneously.

3. The method of claim 1, further comprising skinning the composite ingot to remove at least a portion of the composition gradient zone and the outer zone from a rolling surface.

4. A method as claimed in claim 3, wherein peeling comprises removing material to produce a monolithic ingot comprising the first aluminium alloy.

5. The method of claim 1, wherein the first aluminum alloy comprises a 7xxx series aluminum alloy, a 5xxx series aluminum alloy, or a 2xxx series aluminum alloy.

6. The method of claim 5, wherein the first aluminum alloy comprises 7075 aluminum alloy, 5182 aluminum alloy, or 2024 aluminum alloy.

7. The method of claim 1, wherein the second aluminum alloy comprises a 1xxx series aluminum alloy.

8. The method of claim 7, wherein the second aluminum alloy has a purity of at least 99.7%.

9. The method of claim 1, wherein the at least one alloying element of the first aluminum alloy comprises Zn, cu, mg, or Na.

10. The method of claim 1, wherein the outer region is substantially free of the at least one alloying element.

11. The method of claim 1, wherein the composite ingot is substantially free of cracking.

12. The method of claim 11, wherein cracking comprises cold cracking, thermal cracking, edge cracking, or tail cracking.

13. The method of claim 1, wherein the composite ingot is substantially free of porous structures.

14. The method of claim 13, wherein the porous structure comprises pores that are nucleation sites from fracture during hot rolling.

15. The method of claim 1, wherein casting the composite ingot comprises a direct chill casting process, wherein the inner region and the outer region are co-cast in an arrangement in which the outer region is in contact with cooling water.

16. The method of claim 1, wherein the outer region has a thickness of 7% to 15% of the total thickness of the composite ingot.

17. The method of claim 16, wherein the compositional gradient region has a thickness of 2% to 10% of the total thickness of the composite ingot.

18. The method of claim 1, further comprising processing the ingot to form an aluminum alloy sauter plate, or sheet comprising the first aluminum alloy.

19. The method of claim 1, further comprising one or more of a homogenization process, a hot rolling process, a cold rolling process, an annealing process, a solution heat treatment process, a quenching process, or a surface treatment process.

20. The method of claim 1, further comprising directing a magnetic field during casting, the magnetic field configured to inhibit turbulence in a direction perpendicular to the compositional gradient region.

21. The method of claim 1, wherein the first aluminum alloy is delivered to the mold from a first elevation and the second aluminum alloy is delivered to the mold from a second elevation, wherein the second elevation is different from the first elevation.

22. The method of claim 21, further comprising directing a magnetic field during casting to inhibit turbulence in a direction perpendicular to the compositional gradient region, wherein directing comprises positioning the magnetic field at a height between the first height and the second height.

23. The method of claim 22, comprising directing a magnetic field during casting to inhibit turbulence in a direction perpendicular to the compositional gradient region, wherein directing the magnetic field comprises providing a slag dam positioned at a height within the melt body between the first height and the second height.

24. An aluminum alloy composite ingot produced by the method of any one of claims 1 to 23.

25. An aluminum alloy composite ingot, the aluminum alloy composite ingot comprising:

an inner region comprising a first aluminum alloy,

26. The aluminum alloy composite ingot of claim 25, wherein the first aluminum alloy comprises a 7xxx series aluminum alloy, a 5xxx series aluminum alloy, or a 2xxx series aluminum alloy.

27. The aluminum alloy composite ingot of claim 26, wherein the first aluminum alloy comprises 7075 aluminum alloy, 5182 aluminum alloy, or 2024 aluminum alloy.

28. The aluminum alloy composite ingot of claim 25, wherein the second aluminum alloy comprises a 1xxx series aluminum alloy.

29. The aluminum alloy composite ingot of claim 28, wherein the second aluminum alloy has a purity of at least 99.7%.

30. The aluminum alloy composite ingot of claim 25, wherein the at least one alloying element of the first aluminum alloy comprises Zn, cu, mg, or Na.

31. The aluminum alloy composite ingot of claim 25, wherein the outer region is substantially free of the at least one alloying element.

32. The aluminum alloy composite ingot of claim 25, wherein the composite ingot is substantially free of cracking.

33. The aluminum alloy composite ingot of claim 32, wherein cracking comprises cold cracking, thermal cracking, edge cracking, or tail cracking.

34. The aluminum alloy composite ingot of claim 25, wherein the composite ingot is substantially free of porous structures.

35. The aluminum alloy composite ingot of claim 34, wherein the porous structure comprises pores that are nucleation sites from fracture during hot rolling.

36. The aluminum alloy composite ingot of claim 25, wherein the outer region has a thickness of 7% to 15% of a total thickness of the composite ingot.

37. The aluminum alloy composite ingot of claim 36, wherein the compositional gradient region has a thickness of 2% to 10% of a total thickness of the composite ingot.

38. A rolled aluminium alloy product formed by the method of any one of claims 1 to 23.

39. A rolled aluminum alloy product, the rolled aluminum alloy product comprising:

an inner region comprising a first aluminum alloy,

40. The rolled aluminum alloy product of claim 39, made from the aluminum alloy composite ingot of any of claims 24-37.

41. The rolled aluminum alloy product of claim 39, wherein the first aluminum alloy comprises a 7xxx series aluminum alloy, a 5xxx series aluminum alloy, or a 2xxx series aluminum alloy.

42. The rolled aluminum alloy product as claimed in claim 41, wherein the first aluminum alloy comprises 7075 aluminum alloy, 5182 aluminum alloy, or 2024 aluminum alloy.

43. The rolled aluminum alloy product of claim 39, wherein the second aluminum alloy comprises a 1xxx series aluminum alloy.

44. The rolled aluminum alloy product of claim 43, wherein the second aluminum alloy has a purity of at least 99.7%.

45. The rolled aluminum alloy product of claim 39, wherein the at least one alloying element of the first aluminum alloy comprises Zn, cu, mg, or Na.

46. The rolled aluminum alloy product of claim 39, wherein the outer region is substantially free of the at least one alloying element.

47. The rolled aluminum alloy product of claim 40, wherein the composite ingot is substantially free of cracking.

48. The rolled aluminum alloy product of claim 47, wherein the cracking comprises cold cracking, thermal cracking, edge cracking, or tail cracking.

49. The rolled aluminum alloy product of claim 40, wherein the composite ingot is substantially free of porous structures.

50. The rolled aluminum alloy product of claim 49, wherein the porous structure comprises pores that are nucleation sites from fracture during hot rolling.

51. The rolled aluminum alloy product of claim 40, wherein the outer region has a thickness of 7% to 15% of the total thickness of the composite ingot.

52. The rolled aluminum alloy product of claim 51, wherein the compositional gradient region has a thickness of 2% to 10% of the total thickness of the composite ingot.