Selective Removal of Impurities from Molten Aluminum

The present disclosure concerns using microstructural engineering techniques to remove or reduce impurity elements from molten aluminum alloys, such as scrap. The impurities are removed by cooling molten aluminum, resulting in the formation of impurity-rich intermetallic compounds containing only one or more impurity elements as solid inclusions. Subsequent removal of impurity-rich intermetallic sediments by decantation, centrifuge, and filtration techniques can provide an economical method for removing the desired amount of impurities to meet the product specifications.

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Description
CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application 63/427,484, filed Nov. 23, 2022, and to U.S. Provisional Patent Application 63/580,092, filed Sep. 1, 2023, the contents of which are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present disclosure concerns processes to remove impurities from an aluminum-based melt and the resulting purified alloys therefrom.

BACKGROUND

Aluminum alloys are known for their high strength-to-weight ratio, excellent castability, thermal & electrical conductivities, and outstanding corrosion resistance. This unique combination of properties enables aluminum alloys to be widely used in diverse industries such as automotive, aerospace, packaging, wiring & electrical cables, building & construction, and consumer electronics. Because of its high recyclability, aluminum is a material of choice for a circular economy.

However, during recurring scrap recycling, aluminum recycling can be complicated by the accumulation of unwanted impurities, such as iron (Fe), manganese (Mn), copper (Cu), silicon (Si), zinc (Zn), and magnesium (Mg). The impurity pickup can result in significant economic devaluation of scrap where aluminum products are downcycled to produce aluminum products with lower value and performance. Managing the impurity content of aluminum scrap melt is therefore highly significant.

The scrap used for recycling typically includes many different types of aluminum alloy, with different and varying levels of impurities. This in turn makes it difficult to predict or control the levels or amounts of total impurities, making obtaining a targeted or desired final alloy composition challenging. However, possessing the ability to remove impurities offers the best option to proceed with a higher quality recycled aluminum. The control and removal of impurities from aluminum scrap have become important in a greater range of alloy production as impurity levels are rising with higher utilization of scrap-based secondary aluminum. One of the main impurities in aluminum alloy is iron, which results mainly from charge materials and significantly affects the mechanical properties. In particular, the needle-like β-Al5FeSi intermetallic phase that forms in recycled Al—Si alloys promotes the formation of shrinkage pores and porosity defects, which eventually deteriorate the mechanical properties. Many methods such as adding neutralizing elements (e.g. beryllium (Be), scandium (Sc), strontium (Sr), manganese (Mn), chromium (Cr), cobalt (Co), rare earth metals (RE), molybdenum (Mo), vanadium (V), and boron (B)), adding melt treatment steps, or increasing cooling rates have been employed to improve the mechanical properties and to neutralize the morphology and size of β-Fe phase. While these approaches had some degree of success, the resulting alloys often still fail to match the qualities offered from a primary alloy. Thus, a need is felt for an alloying process that more effectively removes impurities.

SUMMARY OF THE INVENTION

The present disclosure relates to methods to remove impurities from molten aluminum and to the intermetallic metals formed therein/thereby.

A 1st aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns a process for producing an aluminum alloy, comprising:

    • a.) melting an aluminum source at at >725° C. to obtain a melt;
    • b.) adding to the melt with an alloying element at at least >725° C., wherein the alloying element is selected from the group consisting of chromium, vanadium, yttrium, cerium, manganese, or at least two thereof;
    • c.) lowering the temperature of the melt to a lowered holding temperature of about 615° C. to about 725° C.;
    • d.) maintaining melt at the lowered holding temperature for at least about 15 minutes; and
    • e.) removing precipitated impurity-rich intermetallics from the melt to provide the aluminum alloy.

A 2nd aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein alloying element comprises 0.3 to 2.0% by weight of the melt.

A 3rd aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the aluminum source comprises a wrought aluminum and/or a cast aluminum.

A 4th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein holding the melt in step (b) is for a period of time of at least 15 minutes.

A 5th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the temperature of the melt is lowered to the lowered temperature at a cooling rate of at least about 5° C. per minute.

A 6th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the scrap aluminum comprises an iron content of at least 0.2% by weight.

A 7th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the scrap aluminum comprises a silicon content of less than 3% by weight.

An 8th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the scrap aluminum comprises a silicon content of at least 3% by weight.

A 9th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the alloying element comprises manganese.

A 10th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the alloying element comprises chromium.

An 11th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein in the alloying element comprises cerium.

A 12th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the alloying element comprises vanadium.

A 13th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the alloying element comprises yttrium.

A 14th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the alloying element comprises magnesium and chromium.

A 15th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, further comprising raising the silicon content of the melt.

A 16th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the melt is mixed by mechanical stirring.

A 17th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the holding temperature is of about 615 to about 650° C.

An 18th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 1st aspect, wherein the holding temperature allows for formation of iron-manganese impurity-rich intermetallics to initiate.

A 19th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns an impurity-rich intermetallic aluminum alloy comprised of aluminum, 0.01 to 5 wt. % iron, 0.01-5 wt. % manganese, and 0.3-0.5 wt. % of an alloying element selected from the group consisting of chromium, cerium, magnesium, vanadium, yttrium, manganese or a combination thereof.

A 20th aspect, of the present disclosure, either alone or in combination with any other aspect described herein, concerns the impurity-rich intermetallic aluminum alloy of the 19th aspect, further comprising 0 to 12 wt. % silicon.

A 21st aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns process for producing an aluminum alloy, comprising:

    • a.) melting an aluminum source at at least 725° C. to obtain a melt;
    • b.) adding to the melt with an alloying element at at least 725° C., wherein the alloying element is chromium;
    • c.) lowering the temperature of the melt to a lowered holding temperature of about 615° C. to about 725° C.;
    • d.) maintaining melt at the lowered holding temperature for at least about 15 minutes; and
    • e.) removing precipitated impurity-rich intermetallics from the melt to provide the aluminum alloy.

A 22nd aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 21st aspect, wherein alloying element comprises 0.3 to 0.5% by weight of the melt.

A 23rd aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 21st aspect, wherein the aluminum source comprises a wrought aluminum and/or a cast aluminum.

A 24th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 21st aspect, wherein holding the melt in step (b) is for a period of time of at least 15 minutes.

A 25th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 21st aspect, wherein the temperature of the melt is lowered to the lowered temperature at a cooling rate of at least about 5° C. per minute.

A 26th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 21st aspect, wherein the scrap aluminum comprises an iron content of at least 0.2% by weight.

A 27th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 21st aspect, wherein the scrap aluminum comprises a silicon content of less than 3% by weight.

A 28th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 21st aspect, wherein the scrap aluminum comprises a silicon content of at least 3% by weight.

A 29th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 21st aspect, wherein the alloying element comprises magnesium and chromium.

A 30th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 21st aspect, wherein the melt is mixed by mechanical stirring.

A 31st aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 21st aspect, wherein the lowered holding temperature is of about 615 to about 650° C.

A 32nd aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 21st aspect, wherein the cooling rate allows for formation of iron-manganese impurity-rich intermetallics to initiate.

A 33rd aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns a process for producing an aluminum alloy, comprising:

    • a.) melting an aluminum source at at least 725° C. to obtain a melt;
    • b.) adding to the melt with an alloying element at at least 725° C., wherein the alloying element is manganese;
    • c.) lowering the temperature of the melt to a lowered mixing temperature of about 615° C. to about 725° C.;
    • d.) maintaining holding at the lowered mixing temperature for at least about 15 minutes; and
    • e.) removing precipitated impurity-rich intermetallics from the melt to provide the aluminum alloy.

A 34th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 33rd aspect, wherein alloying element comprises 0.3 to 0.5% by weight of the melt.

A 35th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 33rd aspect, wherein the aluminum source comprises a wrought aluminum and/or a cast aluminum.

A 36th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 33rd aspect, wherein holding the melt in step (b) is for a period of time of at least 15 minutes.

A 37th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 33rd aspect, wherein the temperature of the melt is lowered to the lowered temperature at a cooling rate of at least about 5° C. per minute.

A 38th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 33rd aspect, wherein the scrap aluminum comprises an iron content of at least 0.2% by weight.

A 39th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 33rd aspect, wherein the scrap aluminum comprises a silicon content of less than 3% by weight.

A 40th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 33rd aspect, wherein the scrap aluminum comprises a silicon content of at least than 3% by weight.

A 41st aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 33rd aspect, wherein the melt is mixed by mechanical stirring.

A 42nd aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 33rd aspect, wherein the lowered holding temperature is of about 615 to about 650CC.

A 43rd aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 33rd aspect, wherein the cooling rate allows for the formation of iron-manganese impurity-rich intermetallics to initiate.

A 44th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns a process for producing an aluminum alloy comprising:

    • a.) melting an aluminum source at at least 725° C. to obtain a melt;
    • b.) adding to the melt with chromium and magnesium at at least 725° C.;
    • c.) lowering the temperature of the melt to a lowered mixing temperature of about 615° C. to about 725° C.;
    • d.) maintaining holding at the lowered mixing temperature for at least about 15 minutes; and
    • e.) removing precipitated impurity-rich intermetallics from the melt to provide the aluminum alloy.

A 45th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 44th aspect, wherein alloying element comprises 0.3 to 0.5% by weight of the melt.

A 46th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 44th aspect, wherein the aluminum source comprises a wrought aluminum and/or a cast aluminum.

A 47th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 44th aspect, wherein holding the melt in step (b) is for a period of time of at least 15 minutes.

A 48th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 44th aspect, wherein the temperature of the melt is lowered to the lowered temperature at a cooling rate of at least about 5° C. per minute.

A 49th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 44th aspect, wherein the scrap aluminum comprises an iron content of at least 0.2% by weight.

A 50th aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 44th aspect, wherein the scrap aluminum comprises a silicon content of less than 3% by weight.

A 51st aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 44th aspect, wherein the scrap aluminum comprises a silicon content of at least 3% by weight.

A 52nd aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 44th aspect, wherein the melt is mixed by mechanical stirring.

A 53rd aspect of the present disclosure, either alone or in combination with any other aspect described herein, concerns the process of the 44th aspect, wherein the lowered holding temperature is of about 615 to about 650° C.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows the calculated Scheil-Gulliver solidification diagram.

FIG. 2A shows the calculated Scheil-Gulliver solidification diagram.

FIG. 3A shows the calculated Scheil-Gulliver solidification diagram of Al-0.8Si-0.75Fe-0.8Mn-0.5Cr.

FIG. 3B shows the calculated Scheil-Gulliver solidification diagram of Al-0.8Si-0.75Fe-0.8Mn-1Cr (wt. %) alloys.

FIG. 4A shows equilibrium concentration of Fe, Mn and Cr in liquid phase of alloy Al-0.8Si-0.75Fe-0.8Mn-xCr at 700° C. Note: (g) is equivalent to % used in text. Note: X-axis represents Cr in initial composition.

FIG. 4B shows equilibrium concentration of Fe, Mn and Cr in liquid phase of alloy Al-0.8Si-0.75Fe-0.8Mn-xCr at 680° C., calculated from equilibrium phase diagram. Note: (g) is equivalent to % used in text. Note: X-axis represents Cr in initial composition. Note: (g) is equivalent to % used in text. Note: X-axis represents Cr in initial composition.

FIG. 5A shows the calculated Scheil-Gulliver solidification diagram of Al-5Si-0.75Fe-0.8Mn (wt. %) alloys.

FIG. 5B shows the calculated Scheil-Gulliver solidification diagram of Al-7Si-0.75Fe-0.8Mn (wt. %) alloys.

FIG. 6A shows equilibrium concentration of Fe, Mn and Si in liquid phase of alloy Al-7Si-0.75Fe-xMn during solidification at 620° C., calculated from equilibrium phase diagram. Note (g) is equivalent to % used in text.

FIG. 6B shows equilibrium concentration of Fe, Mn and Si in liquid phase of alloy Al-7Si-0.75Fe-xMn during solidification at 615° C., calculated from equilibrium phase diagram. Note (g) is equivalent to % used in text.

FIG. 7 shows equilibrium concentration of Fe, Mn and Si in liquid phase of alloy Al-7Si-1.5Fe-xMn (where x=0-2%) during solidification at 620° C., calculated from equilibrium phase diagram. Note (g) is equivalent to % used in text.

FIG. 8A shows the calculated Scheil-Gulliver solidification diagram of Al-5Si-0.75Fe-0.8Mn-0.5Cr (wt. %) alloys.

FIG. 8B shows the calculated Scheil-Gulliver solidification diagram of Al-7Si-0.75Fe-0.8Mn-1Cr (wt. %) alloys.

FIG. 9A shows equilibrium concentration of Fe, Mn and Cr in liquid phase of alloy Al-7Si-0.75Fe-0.8Mn-xCr during solidification at 640° C., calculated from equilibrium phase diagram. Note: (g) is equivalent to % used in text. Note: X-axis represents Cr in initial composition.

FIG. 9B shows equilibrium concentration of Fe, Mn and Cr in liquid phase of alloy Al-7Si-0.75Fe-0.8Mn-xCr during solidification at 620° C., calculated from equilibrium phase diagram. Note: (g) is equivalent to % used in text. Note: X-axis represents Cr in initial composition.

FIG. 10A shows SEM-EDS analyses of precipitated impurity-rich intermetallic particles for only Mn.

FIG. 10B shows SEM-EDS analyses of precipitated impurity-rich intermetallic particles for both Mn and Cr.

FIG. 11A shows the effect of 0.3% Mn addition on Fe reduction at a holding temperature of 630° C. for the alloy SI=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2.

FIG. 11B shows the effect of 0.5% Mn addition on Fe reduction at a holding temperature of 630° C. for the alloy SI=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2.

FIG. 11C shows the effect of 1.0% Mn addition on Fe reduction at a holding temperature of 630° C. for the alloy SI=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2.

FIG. 12A shows the effect of 0.3% Mn addition on Fe reduction at a holding temperature of 615° C. for the alloy SI=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2.

FIG. 12B shows the effect of 0.5% Mn addition on Fe reduction at a holding temperature of 615° C. for the alloy SI=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2.

FIG. 12C shows the effect of 1.0% Mn addition on Fe reduction at a holding temperature of 615° C. for the alloy SI=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2.

FIG. 13A shows the effect of 1% Mn and 0.3% Cr addition on Fe reduction at a holding temperature of 630° C. for the alloy SI=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2.

FIG. 13B shows the effect of 1% Mn and 0.5% Cr addition on Fe reduction at a holding temperature of 630° C. for the alloy SI=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2.

FIG. 13C shows the effect of 1% Mn and 0.8% Cr addition on Fe reduction at a holding temperature of 630° C. for the alloy SI=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2.

FIG. 14A shows the effect of 1% Mn and 0.3% Cr addition on Fe reduction at a holding temperature of 615° C. for the alloy SI=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2.

FIG. 14B shows the effect of 1% Mn and 0.5% Cr addition on Fe reduction at a holding temperature of 615° C. for the alloy SI=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2.

FIG. 14C shows the effect of 1% Mn and 0.8% Cr addition on Fe reduction at a holding temperature of 615° C. for the alloy SI=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2.

 DESCRIPTION

The present disclosure concerns a process to effectively remove major impurities from an aluminum source. Using aluminum microstructural engineering, impurity elements can be removed. In part, the removal of impurities can be accomplished by cooling a molten aluminum and allowing impurity-rich intermetallic compounds or crystals containing one or more impurity element to form as solid inclusions. In some aspects, the formation of the impurity-rich intermetallics occurs when the molten aluminum containing the impurity element is hypereutectic. In some aspects, the subsequent impurity-rich intermetallic sediments or precipitates can removed, leaving a purified aluminum alloy by decantation, filtration, or similar techniques.

In some aspects, the present disclosure concerns establishing a melt. In some aspects, the melt includes aluminum. In some aspects, the melt of an aluminum alloy is to be recycled. In some aspects, the melt is two or more different alloys. In some aspects, the melt is of scrap aluminum. In some aspects, the melt is of wrought aluminum, cast aluminum, or a combination thereof. In some aspects, the melt includes one or more impurities to be removed therefrom. In some aspects, the material for the melt is scrap aluminum. In some aspects, the material is an aluminum-bearing by-product of a prior external or internal process. In some aspects, the scrap aluminum includes at least two different aluminum alloys. In some aspects, the scrap aluminum includes iron and/or silicon. In some aspects, at least about 3% of the weight of the scrap aluminum is silicon. In some aspects, the scrap aluminum includes less than about 3% by weight silicon. In some aspects, iron will make up at least 0.2% of the weight of the scrap aluminum.

In some aspects, the present disclosure concerns providing a temperature to melt the entirety of the alloy(s) being treated. In some aspects, such may include providing a temperature sufficient to melt all elements in the alloy. In some aspects, such may be of about 725° C. or greater. In some aspects, the melting temperature is provided for a sufficient period of time to ensure that the entirety of the materials being treated are in a molten state. Such may be varied based on the temperature utilized and the volume of material. In some aspects, it can take a period of between about 15 minutes to 120 minutes or longer, including about 20, 30, 40, 50, 60, 70, 80, 90, 100, and 110 minutes or more.

In aspects, the present disclosure concerns adding an alloying element to a melt of aluminum. In some aspects, the alloying element can be one of chromium (Cr), vanadium (V), yttrium (Y), cerium (Ce), manganese (Mn), or a combination thereof. In some aspects, the alloying element(s) is added at a weight percentage of the melt of from at about 0.2 wt. %, including at least about 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, and 5.0, or higher wt. %. In some aspects, the alloying element is melted in the melt. In some aspects, the melt is mixed, stirred, held, or agitated to allow for the even distribution of the alloying element(s) within the melt. In some aspects, the melt is mixed by mechanical stirring. In some aspects, the melt of the alloying element(s) and the aluminum alloy(s) is incubated at at a temperature of about 725° C. or greater for a period of time of about 10 minutes or longer, such as about 15, 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 or longer. It will be appreciated that the length of time, as well as other co-factors such as the concentration of impurities in the aluminum alloy(s) and the amount of alloying element, can contribute to the concentration or amount of impurity-rich intermetallics that can form within the melt.

In some aspects, the present disclosure concerns lowering the temperature of the melt of the aluminum alloy(s) and the alloying element(s) to a temperature above the melting point of aluminum. In some aspects, the temperature is lowered to about 615 to about 725° C., including about 620, 625, 630, 635, 640, 645, 650, 655, 660, 665, 670, 675, 680-, 685, 690, 695, 700, 705, and 710° C. (±4/3/2/1° C.). In some aspects, the temperature is lowered at a cooling rate of at least about 5° C. per minute. In some aspects, the cooling rate is from about 5 to about 15° C. per minute, including about 6, 7, 8, 9, 10, 11, 12, 13, and 14° C. per minute. It is an aspect of the present disclosure that the cooling rate can allow impurity-rich intermetallics as described herein to initiate their formation. In some aspects, the temperature is lowered and maintained within the lowered range for a period of time to allow for impurity-rich intermetallics formed therein to solidify. In some aspects, the temperature of the melt is maintained at about 615-725° C. for a period of time from about 15 minutes to about 120 minutes, including about 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, and 115 minutes (±4/3/2/1° C.). In some aspects, the impurity-rich intermetallics formed solidify and/or precipitate from the melt before α-Al in the melt will solidify, allowing for the isolation of the impurity-rich intermetallics from the α-Al in the melt. In some aspects, the alloying element(s) provide for an impurity-rich intermetallic product with a higher melting point than α-Al, thereby allowing for the impurity-rich intermetallic to solidify and/or precipitate and/or sediment within the melt. In some aspects, such can be removed or filtered from the melt. In some aspects, the temperature of the melt is then further lowered to allow the purified alloy to solidify. In some aspects, the purified alloy has an iron content of about 0.2 wt. %. In some aspects, the iron content in the purified alloy has been reduced by at least 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75% or higher from the original aluminum alloy(s). In some aspects, the purified alloy has a manganese content of about 0.2 wt. %. In some aspects, the manganese content in the purified alloy has been reduced by at least 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75% or higher from the original aluminum alloy(s).

It is a purpose of the present disclosure to provide at least two distinct products from the processes of the present disclosure. In some aspects, the present disclosure provides for a purified aluminum or aluminum alloy, wherein the concentration of Fe and/or Mn and other undesirable or contaminating elements has been reduced and/or removed. In some aspects, the present disclosure concerns the formation of one or more impurity-rich intermetallics. In some aspects, the impurity-rich intermetallics include iron and/or manganese. In some aspects, the impurity-rich intermetallics include aluminum, iron, manganese, and silicon. In some aspects, the impurity-rich intermetallics include iron, aluminum, manganese, silicon and chromium. In some aspects, the impurity-rich intermetallics include aluminum, iron, manganese, chromium, silicon, and magnesium. In some aspects, the impurity-rich intermetallics include iron, aluminum, manganese, silicon and vanadium. In some aspects, the impurity-rich intermetallics include aluminum, iron, manganese, vanadium, silicon, and magnesium. In some aspects, the impurity-rich intermetallics include iron, aluminum, manganese, silicon and cerium. In some aspects, the impurity-rich intermetallics include aluminum, iron, manganese, cerium, silicon, and magnesium. In some aspects, the impurity-rich intermetallics include iron, aluminum, manganese, silicon and yttrium. In some aspects, the impurity-rich intermetallics include aluminum, iron, manganese, yttrium, silicon, and magnesium.

In some aspects, the impurity-rich intermetallics concentrate the iron and/or manganese from the melted aluminum alloy(s), providing an impurity-rich intermetallic that is 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0 or more time higher of iron and/or manganese in the impurity-rich intermetallic than in the original alloy(s). In some aspects, the concentration of iron and/or manganese in the impurity-rich intermetallics is dependent on the alloy(s) used in the melt. In some aspects, the impurity-rich intermetallics formed predominantly include Al, such as from about 80-99.9 wt. %, including about 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, and 99 wt. % (±0.01/0.1/1 wt. %). In some aspects, the impurity-rich intermetallics form include Si at about 0.01 to 10 wt. %, including about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, and 9 wt. % (±0.01/0.1/1 wt. %). In some aspects, the impurity-rich intermetallics formed include Cr at about 0.01 to 10 wt. %, including about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, and 9 wt. % (±0.01/0.1/1 wt. %). In some aspects, the impurity-rich intermetallics formed include Mn at about 0.01 to 10 wt. %, including about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, and 9 wt. % (±0.01/0.1/1 wt. %). In some aspects, the impurity-rich intermetallics formed include Mg at about 0.01 to 10 wt. %, including about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, and 9 wt. % (±0.01/0.1/1 wt. %). In some aspects, the impurity-rich intermetallics formed include Ce at about 0.01 to 10 wt. %, including about 00.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, and 9 wt. % (±0.01/0.1/1 wt. %). In some aspects, the impurity-rich intermetallics formed include Y at about 0.01 to 10 wt. %, including about 00.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, and 9 wt. % (±0.01/0.1/1 wt. %). In some aspects, the impurity-rich intermetallics formed include V at about 0.01 to 10 wt. %, including about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, and 9 wt. % (±0.01/0.1/1 wt. %).

Contaminating or undesirable elements from the alloy, such as iron (Fe) and manganese (Mn) can be removed by providing the molten alloy melt with a concentration of an alloying element, such as one or more of chromium (Cr), vanadium (V), yttrium (Y), cerium (Ce), manganese (Mn), magnesium (Mg), or a combination thereof, thereby forming impurity-rich intermetallic compounds that include Fe, Mn, and Si and subsequent removal of impurity-rich intermetallic sediments or precipitates by decantation, centrifuge, filtration, or similar techniques.

It is an aspect of the present disclosure that the holding temperature for the formation and separation of the impurity-rich intermetallic phases can be kept above the solidification temperature of α-Al.

In some aspects, the alloying element includes manganese. In some aspects, the alloying element includes chromium. In some aspects, the alloying elements include manganese and chromium. The addition of Chromium (Cr) metal in the molten aluminum expedites the kinetics and extent of the formation and sedimentation of impurity-rich intermetallic particles. Both Mg and Si facilitate Fe and Mn removal by lowering the eutectic temperature and increasing the fluidity of the melt. Holding temperature plays an important role in the formation of impurity-rich intermetallic and reduction. Direct or indirect stirring, agitation, or other methods will expedite the formation and removal of specific impurity-rich intermetallic compounds. FIGS. 3a and 3b show calculated solidification sequences of Al-0.8Si-0.75Fe-0.8Mn-0.5/1Cr (wt. %) alloy. FIG. 1 shows that the alloy includes α-AlFeMnCrSi phase, α-Al, Al13Fe4, and Al9Fe2Si2, and many other phases in the nonequilibrium solidification. Cr promotes the formation of impurity-rich intermetallic phases in low Si alloys, which may then allow for the removal of Fe/Mn via impurity-rich intermetallic precipitation-sedimentation route. α-AlFeMnCrSi is the primary phase during solidification, and the presence of high Cr concentration widens the temperature range (709°-734° C.) for the precipitation of the impurity rich intermetallic phase by increasing the transformation temperature at which they start appearing. Like Mn, the addition of Cr does not affect the α-Al phase formation temperature and, therefore, the holding temperature for the formation and separation of the impurity-rich intermetallic phases can be kept above the solidification temperature of α-Al. In some aspects, the impurity-rich metallic include AlFeMnCr, AlFeMnCrSi, AlFeMnCrMgSi, and combinations thereof. In some aspects, the impurity-rich intermetallics formed include 0.01-3 wt. % Cr. In some aspects, the impurity-rich intermetallics formed include Al-0.50-4.0Fe-0.5-4Cr (wt. %), Al-0.50-4.0Cr-0.5-4Mn (wt. %), Al-0.50-4.0Fe-0.5-4Mn-0.50-4.0Cr (wt. %), Al-0.50-4.0Fe-0.5-4Cr-0.5-8Si (wt. %), Al-0.50-4.0Cr-0.5-4Mn-0.5-8Si (wt. %) Al-0.50-4.0Fe-0.5-4Mn-0.5-4.0Cr-0.5-8Si (wt. %), and/or Al-0.50-4.0Fe-0.5-4Mn-0.5-4.0Cr-0.5-4.0Mg-0.5-8Si (wt. %). In some aspects, the impurity-rich intermetallics include Al-0.8Si-0.75Fe-0.8Mn-0.5Cr, Al-0.8Si-0.75Fe-0.8Mn-1Cr (wt. %) alloys, and/or Al-0.8Si-0.75Fe-0.8Mn-0.5/1Cr (wt. %) alloy. In some aspects, the impurity-rich intermetallic include Al-0.8Si-0.75Fe-0.8Mn-xCr (wt. %), wherein x is of 0-2 wt. %, including about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9 wt. % (±0.01/0.02/0.03/0.04/0.05/0.06/0.07/0.08/0.09 wt. %). In some aspects, the impurity-rich intermetallic(s) formed include AlFeMnCrSi, AlFeMnCrMgSi, or combinations thereof.

FIG. 4 shows the variation in the iron and manganese in the liquid phase by varying the weight percentage of chromium addition at different holding temperatures for the alloy Al-0.8Si-0.75Fe-0.8Mn-xCr (where x=0-2%). The iron content in the liquid aluminum can decrease significantly with increasing chromium, according to the thermodynamic calculations. For example, when Cr=˜0.9% in FIG. 4(a), the equilibrium concentration of Fe was decreased from 0.75% to 0.45% at 700° C. in the liquid phase. At the same time, when the holding temperature decreased to 680° C. the initial content of 0.75% Fe decreased to 0.35% Fe in the liquid phase, showing a significant effect of holding temperature on the possibility of Fe reduction. The addition of Cr in low Si alloy promotes the Fe-rich phase precipitation first from the liquid phase.

In some aspects, the impurity-rich intermetallic(s) formed include manganese when manganese is included as an alloying element, such as Al, Mn, AlFeMn, AlFeMnSi, AlFeMnMgSi, and combinations thereof. In some aspects, the impurity-rich intermetallics formed include Al-0.50-4.0Mn (wt. %), Al-0.50-4.0Fe-0.5-4Mn (wt. %), Al-0.50-4.0Fe-0.5-8Si (wt. %), Al0.5-4Mn-0.5-8Si (wt. %) Al-0.50-4.0Fe-0.5-4Mn0.5-8Si (wt. %), and/or Al-0.50-4.0Fe-0.5-4Mn-0.5-4.0Mg-0.5-8Si (wt. %). In some aspects, the impurity-rich intermetallics include Al-0.8Si-0.75Fe-0.8Mn, Al-0.8Si-0.75Fe-0.8Mn (wt. %) alloys, and/or Al-0.8Si-0.75Fe-0.8Mn (wt. %) alloy.

In some aspects, the alloying element includes manganese. The removal of Fe and Mn via precipitation of Fe/Mn-rich impurity-rich intermetallics formation requires fine control of the temperature for the formation of the primary phases and may depend on the other alloying elements associated with specific alloy compositions. Computational thermodynamic analysis can assist in determining whether an alloy with Fe will form impurity-rich intermetallics and at what temperature they will form. FIG. 1 shows calculated solidification sequences and solidified phase fraction of Al-0.8Si-0.75Fe-0.8Mn (wt. %) alloy, showing that the alloy consists of mainly Al13Fe4, α-Al, Al6Mn, Al15(FeMn)3Si2 and Al9Fe2Si2 phases in the nonequilibrium solidification. A higher precipitation temperature than that of α-Al (652° C.) allows for the physical separation of any impurity-rich intermetallic phases. A higher concentration of Mn in Al-alloys (see FIG. 2) promotes the formation Al6Mn impurity-rich intermetallic phase prior to α-Al solidification and increases the solidification temperature of scrap aluminum. Mn alone is not particularly effective at lowering the Fe content from low Si-containing Al-alloy. In higher Si melts, Mn can be more effective.

In some aspects, the impurity-rich intermetallic(s) formed include manganese when manganese is included as an alloying element, such as AlFeMnSi. In some aspects, the impurity-rich intermetallics include Al-0.50-4.0Fe-0.5-4Mn (wt. %) and/or Al-0.50-4.0Fe-0.5-4Mn-0.5-8Si (wt. %). In some aspects, the impurity-rich intermetallics include Al-0.84Fe-0.92Mn-0.8Si (wt. %), Al-1.01Fe-0.84Mn-0.66Si, Al-0.84Fe-0.92Mn-0.8Si, Al-0.88Fe-0.9Mn-1.38Si, Al-1.45Fe-1.9Mn-1.8Si-7.3Mg, Al-1.3Fe-1.7Mn-1.7Si-10.6Mg, and/or Al-1.2Fe-1.0Mn-1.8Si (wt. %). In some aspects, the impurity-rich intermetallics include Al-5-7Si-0.75Fe-0.8Mn (wt. %), including 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 wt. % Si. In some aspects, the impurity-rich intermetallics include Al-0.8Si-0.75Fe-2Mn and/or Al-7Si-1.5Fe-0-2Mn (wt. %). In some aspects, the impurity-rich intermetallics may include magnesium (Mg), such as at 0.5-15.0 wt. %. In some aspects, the alloy compositions used for the melt include Al-0.73Fe-0.90Mn-0.94Si—0.87Zn-0.69Cu, Al-0.62Fe-0.41Mn-6.58Si—0.36Cu-0.31Mg-0.13Ti, Al-0.52Fe-0.4Mn-6.3Si—0.3Cu-0.32Mg-0.13Ti, Al-1.3Fe-1.2Mn-8.7Si-2.61Zn-4.19Cu0.24Mg, Al-1.2Fe-1.32Mn-7.52S-2.59Zn-4.18Cu-0.3Mg, Al-0.73Fe-0.8Mn-0.22Cu-5.8Si, Al-0.9Fe-0.9Mn-0.22Cu-5.06Si (wt. %) (±0.01/0.02/0.03/0.04/0.05/0.06/0.07/0.08/0.09 wt. %) and/or combinations thereof.

In some aspects, the alloying element includes silicon. The addition of silicon to aluminum reduces the melting temperature range and improves fluidity. From calculated solidification sequences of Al-xSi-0.75Fe-0.8Mn (wt. %) alloy, it was observed that impurity-rich intermetallics phases are formed beforehand above 5% Si (wt. %) concentration. FIG. 5 shows calculated solidification sequences of Al-5/7Si-0.75Fe-0.8Mn (wt. %) alloys. As can be seen, the presence of high Si not only decreased the solidification temperature of the α-Al phase to 628° C. (5% Si) and 614° C. (7% Si) but also widened the formation temperature for impurity-rich intermetallic phases. FIG. 6 shows the variation in the concentrations of Fe, Mn, and Si in the liquid phase by varying the weight percentage of Mn addition at different holding temperatures (620° C. and 615° C.) for the alloy with lower Fe content [Al-7Si-0.75Fe-xMn (where x=0.5-2%)]. It was observed that the final equilibrium concentrations of Fe and Mn in the liquid phase were significantly reduced when keeping the temperature above the solidification temperature of α-Al phase. However, the reduction is not very significant when reducing temperature from 620-615° C. The equilibrium concentration of Fe decreased from 0.75% to 0.45% at 620° C. in the liquid phase when the initial content of Mn was 2%, which further decreased to 0.74% Mn in the liquid phase, showing a significant reduction. The content of Si only showed a slight reduction from 7% to 6.5% at 620° C. in the liquid phase. The variation of Fe, Mn and Si concentrations during solidification at holding temperature of 620° C. was also investigated by calculating the equilibrium concentration in the liquid phase for the alloy with higher initial Fe concentration [Al-7Si-1.5Fe-xMn (where x=0-2%)] (see, FIG. 7). The equilibrium Fe content was decreased from initial 1.5% to 0.75% when adding 2% Mn in the initial alloy composition. The equilibrium Mn concentration decreased from 2% to 0.6%, whereas the Si content decreased to 6.3% at the same temperature. The thermodynamic calculation results suggest that Mn and Fe concentrations can be substantially reduced from an alloy with high Si concentration.

In some aspects, the alloying element includes yttrium, cerium or, vanadium, such as AlFeMnY, AlFeMnCe, and/or AlFeMnV. In some aspects, the impurity-rich intermetallic formed includes Al-0.75Fe-0.8Mn-5Y (wt. %) (±0.01/0.02/0.03/0.04/0.05/0.06/0.07/0.08/0.09 wt. %).

In some aspects, providing two or more alloying elements may provide for even further reduction of contaminating elements from the melt. In some aspects, the alloying element includes manganese and chromium. As set forth in the working examples herein, the inclusion of Mn (1 wt. %) and Cr (0.8 wt. %) allowed for over 70% reduction in the melt of iron and manganese despite the starting material containing over 1% of both.

In some aspects, the present disclosure concerns allowing the impurity-rich intermetallics described herein to form in the metal. In further aspects, the impurity-rich intermetallics described herein will solidify in the melt as the temperature is lowered, while the α-Al remains molten. In some aspects, the impurity-rich intermetallics as described herein are removed from the melt. For example, some impurity-rich intermetallics may precipitate or drop to the bottom of the melt, allowing for separation of the impurity-rich intermetallics as described herein. In some aspects, a mesh may be utilized to retrieve and/or isolate the impurity-rich intermetallics from the melt after solidification therein. For example, numerous metals such as stainless steel, tungsten, and nickel all have melting points above temperature required to provide the melt as described herein and can accordingly be fabricated to a mesh or similar filtering shape to allow for the solidified impurity-rich intermetallics to sediment thereon and remove the same from the melt. In further aspects, the melt is allowed to cool to provide a purified aluminum or aluminum alloy. As set forth herein, the formation of the impurity-rich intermetallics as described herein can remove iron and/or manganese from the melt. In some aspects, the metal can then be cast and/or provided to a mold to provide a desired shape and/or configuration to the purified aluminum and/or aluminum alloy.

In some aspects, the addition of the alloying element and the steps described herein concerning temperature control of the melt allow for contaminating elements such as iron and/or manganese to be removed or reduced in concentration from the molten aluminum, allowing for a purified α-Al or alloy thereof. In some aspects, purification may include about 25 to 100% removal of iron and/or manganese from the melt. In some aspects, additional elements, such as zinc, titanium, copper, and magnesium may similarly be removed and/or reduced in concentration from the melt.

EXAMPLES

The removal of Fe and Mn via precipitation of Fe/Mn rich impurity-rich intermetallics formation requires control of the temperature for the formation of the primary phases and depends on the other alloying elements associated with specific alloy compositions. Computational thermodynamic analysis helps determine whether an alloy with Fe will form impurity rich intermetallics and at what temperature they will form. Calculations were performed on phases present as a function of temperature and composition using the software ThermoCalc with the commercial database TCAL8. The calculations were made using the Scheil-Gulliver solidification model that assumes equilibrium only in the liquid and at the solid-liquid interface, but no solid-state diffusion. FIG. 1A shows the calculated solidification sequences and solidified phase fraction of Al-0.8Si-0.75Fe-0.8Mn (wt. %) alloy showing that the alloy consists of mainly Al13Fe4, α-Al, Al6Mn, Al15Si2M4 and Al9Fe2Si2 phases in the nonequilibrium solidification. Note that all the impurity-rich intermetallic phases precipitated out after the solidification of α-Al. A higher precipitation temperature than that of α-Al (652° C.) is necessary for the physical separation of any impurity rich intermetallic phases. Higher concentration of Mn in Al-alloys (FIG. 2A) promotes the formation Al6Mn impurity-rich intermetallic phase prior to α-Al solidification and increases the solidification temperature of scrap aluminum suggesting that removal of Fe from wrought aluminum alloys via the Fe-rich impurity-rich intermetallic phase precipitation route is not particularly effective when using the high Mn concentration alone.

FIGS. 3A and 3B present the calculated solidification sequences of Al-0.8Si-0.75Fe-0.8Mn-0.5/1Cr (wt. %) alloy in these studies. They show that the alloy consists of Al15Si2M4 (α-AlFeMnCrSi) phase, α-Al, Al13Fe4, and Al9Fe2Si2 phases in the nonequilibrium solidification. Unlike Mn, Cr promotes the formation of impurity rich intermetallic phases in low Si alloys which suggests the possibility of removal of Fe/Mn via impurity-rich intermetallic precipitation-sedimentation route. α-AlFeMnCrSi is the primary phase during solidification and presence of high Cr concentration widens the temperature range (709°-734° C.) for the precipitation of the impurity rich intermetallic phase by increasing the transformation temperature at which they start appearing. Like Mn, the addition of Cr does not affect the α-Al phase formation temperature and, therefore, the holding temperature for the formation and separation of the impurity-rich intermetallic phases can be kept above the solidification temperature of α-Al (˜660° C.). FIG. 4 shows the variation in the iron and manganese in the liquid phase by varying the weight percentage of chromium addition at different holding temperature for the alloy Al-0.8Si-0.75Fe-0.8Mn-xCr (where x=0-2%). The iron content in the liquid aluminum decreases significantly with increasing chromium according to the thermodynamic calculations. When Cr=˜0.9% in FIG. 4(a), the equilibrium concentration of Fe was decreased from 0.75% to 0.45% at 700° C. in the liquid phase. At the same time, when the holding temperature decreased to 680° C. the initial content of 0.75% Fe decreased to 0.35% Fe in the liquid phase, showing a significant effect of holding temperature on the possibility of Fe reduction. However, very minor decrease in Mn concentration has been predicted (note scaling to right). Furthermore, in both the cases high concentration of Cr (˜0.56 and ˜0.37%) remained in the melt. Thus, experimental validation is necessary to confirm the thermodynamic calculation prediction.

The addition of silicon to aluminum reduces melting temperature range and improves fluidity. For Fe/Mn removal from Al—Si alloy, it is important to know the Si concentration value that could facilitate the formation and easy sedimentation of Fe/Mn-rich impurity-rich intermetallic phases. From calculated solidification sequences of Al-xSi-0.75Fe-0.8Mn (wt. %) alloy it was observed that impurity rich intermetallics phases are formed beforehand only above 5% Si concentration. FIG. 5 is the calculated solidification sequences of Al-5/7Si-0.75Fe-0.8Mn (wt. %) alloys. As can be seen the presence of high Si not only decreased the solidification temperature of α-Al phase to 628° C. (5% Si) and 614° C. (7% Si) but also widens the formation temperature for impurity rich intermetallic phases.

FIG. 6 shows the variation in the concentrations of Fe, Mn and Si in the liquid phase by varying the weight percentage of Mn addition at different holding temperatures (620° C. and 615° C.) for the alloy with lower Fe content [Al-7Si-0.75Fe-xMn (where x=0.5-2%)]. It was observed that the final equilibrium concentrations of Fe and Mn in the liquid phase were significantly reduced when keeping the temperature above the solidification temperature of α-Al phase. However, the reduction is not very significant when reducing temperature from 620-615° C. The equilibrium concentration of Fe was decreased from 0.75% to 0.45% at 620° C. in the liquid phase when the initial content of Mn was 2% which further decreased to 0.74% Mn in the liquid phase, showing a significant reduction. However, the content of Si only showed a slight reduction from 7% to 6.5% at 620° C. in the liquid phase. The variation of Fe, Mn and Si concentrations during solidification at a holding temperature of 620° C. was also investigated by calculating the equilibrium concentration in the liquid phase for the alloy with higher initial Fe concentration [Al-7Si-1.5Fe-xMn (where x=0-2%)] (FIG. 7). The equilibrium Fe content was decreased from initial 1.5% to 0.75% when adding 2% Mn in the initial alloy composition. The equilibrium Mn concentration decreased from 2% to 0.6%, whereas the Si content decreased to 6.3% at the same temperature. The thermodynamic calculation results suggest that Mn and Fe concentrations can be substantially reduced from an alloy with high Si concentration.

The equilibrium solidification curve of the alloys with adding Cr is shown in FIG. 8. FIGS. 8a and b show that the primary α-Al(FeMnCr)Si impurity-rich intermetallic phases were formed before the solidification of α-Al phase, with the addition of Cr. Furthermore, the initial formation temperature of impurity-rich intermetallics significantly increased to 740° C. and 764° C. when Cr concentration increased from 0.5% to 1%, respectively. In other words, the higher the Cr content, the higher the initial formation temperature. FIG. 9 shows the expected effect of Cr addition on the Fe and Mn levels in the liquid phase when the alloy is maintained at different holding temperatures of 640° C. and 620° C. As can be seen, the Fe level can be theoretically reduced to 0.1% Fe irrespective of holding temperature when Cr is added up to 1% in the initial composition. At the same time, the Mn concentration can be reduced from 0.8% to 0.55% using the same concentration of Cr at 620° C. which suggests that addition of Cr is highly effective, most significantly for the reducing Fe in a high Si alloy. The small residual Cr concentration left in the melt would benefit the mechanical properties.

Experimental alloys (low and high Si) with different Si, Fe, Cr and Mn levels were prepared by mixing a primary unalloyed aluminum (P1020) with commercial Al-25Fe, Al-20Cr, Al-25Mn, master alloys and pure Si chips. The chemical composition of the ingots was tested by Optical Emission Spectrometer (SpectroMaxx LMM-14, Kleve, Germany). During experiments ˜2 kg of the prepared alloys were remelted at >725° C. in a muffle furnace with the addition of the required amounts of Mn or Cr and then dropped to known temperatures in the furnace and held for certain time. In case of low Si alloy, after experiment the furnace was switched off and melt was allowed to cool in the furnace. The final compositions were determined after cutting the melt longitudinally. In the case of high Si alloy, a known amount of the melt was poured into a graphite crucible to analyze the composition and the rest of the melt was allowed to cool in the furnace. Samples for microstructure analysis were prepared using standard metallographic techniques.

Experiments were conducted using alloys with high Si content in the presence of Cr. FIGS. 11A-11C show the Effect of Mn on Fe reduction at holding temp. of 630° C. with the parameters: Alloy: Si=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2. FIGS. 12A-12C show the effect of Mn on Fe reduction at holding temp. of 615° C. with the parameters: Alloy: Si=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2. Fe and Mn contents gradually reduced as the holding temperature decreased. FIGS. 13A-13C show the effect of Mn and Cr on Fe reduction at holding temp. of 630° C. with the parameters: Alloy: Si=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2. FIGS. 14A-14C show the effect of Mn and Cr on Fe reduction at holding temp. of 615° C. with the parameters: Alloy: Si=7.56, Fe=1.22, Mn=0.16, Cu=3.5, Ti=0.08, Mg=0.2. Table 1 shows the effect of only Cr on removal of Fe from A380 alloy scrap with the parameters: Alloy: Si=7.56, Fe=1.22, Mn=0.012, Cu=3.5, Ti=0.08, Mg=0.33 at holding temperature: 630° C.

TABLE 1 Cr = 0.3% Cr = 0.5% Cr = 0.8% Cr = 1% addition addition addition addition Fe wt. % Residual Fe wt. % Residual Fe wt. % Residual Fe wt. % Residual Time (% Red.) Cr (% Red.) Cr (% Red.) Cr (% Red.) Cr 1 h 1.22 0.28 0.93 0.31 0.80 0.37 0.68 0.42 (0.0) (24) (34) (44)

Table 2 shows the same but at holding temperature: 615° C.

Cr = 0.3% Cr = 0.5% Cr = 0.8% Cr = 1% addition addition addition addition Fe wt. % Residual Fe wt. % Residual Fe wt. % Residual Fe wt. % Residual Time (% Red.) Cr (% Red.) Cr (% Red.) Cr (% Red.) Cr 1 h 1.09 0.26 0.83 0.24 0.70 0.28 0.56 0.34 (11) (32) (43) (54)

Table 3 summarizes the chemical composition of the initial alloy and the percent reduction in Fe and Mn content after impurity-rich intermetallics sedimentation. As can be seen, there is a certain decrease after prolonged sedimentation time in the concentration of Fe and Mn in the separated alloy after Cr addition.

TABLE 3 Effect of Cr on Fe/Mn removal from low Si containing Al-alloys. Initial Al- Alloy Cr Temp° C. Final Fe conc. Final Mn conc. Final Cr in composition (%) (time) (% Fe reduction) (% Mn reduction) melt Fe = 0.84%; Mn = 0.92%, 1.1% 660° C. 0.67% (20) 0.69% (25) 0.32% Si = 0.8% Fe = 0.73%; Mn = 0.9%, 0.85% 660° C. 0.56% (23) 0.72% (20) 0.25% Si = 0.94%; Zn = 0.87%, Cu = 0.69%

The cooling curves were also obtained for high Si containing Al-alloys (A380) in absence and presence of Cr.

The presence of high Si in the system not only increases the fluidity but also reduces the temperature for the formation of the α-Al phase (615° C.), thereby promoting the formation of impurity-rich intermetallic phases before the solidification of aluminum. This increases the chance of nucleation and growth of impurity-rich intermetallic phases. Table 4 summarizes the chemical composition of the initial alloy and the percent reduction in Fe and Mn content after impurity-rich intermetallics sedimentation. Based on these results, high Si in the system helps result in faster sedimentation of impurity-rich intermetallic particles as they form. A significant decrease in Fe and Mn levels was observed in the absence of Cr as well. A synergistic effect was observed in iron removal by sediment separation with chromium and manganese simultaneously added to high Si alloy.

TABLE 4 Effect of Cr on Fe/Mn removal from high Si containing Al-alloys. Initial Al- Alloy Mn/Cr Temp° C. Final Fe conc. Final Mn conc. Final Cr in composition (%) (time) (% Fe reduction) (% Mn reduction) melt Si = 7.56, Fe = 1.22, 1% Mn 630° C. (1 h) 0.66% (46) 0.54% (56) 0.0% Mn = 0.16, Cu = 3.5, Ti = 0.08, Mg = 0.2 Si = 7.56, Fe = 1.22, 1% Mn + 630° C. (1 h) 0.35% (71) 0.37% (70) 0.18% Mn = 0.16, Cu = 3.5, 0.8% Cr Ti = 0.08, Mg = 0.2

SEM-EDS analysis was conducted on the impurity rich intermetallics that settled on the bottom of the furnace in both experiments. The EDS analysis (FIG. 10) confirms the formation of α-Al(FeMn)Si impurity-rich intermetallic phase in the impurity rich intermetallics formed when Mn was used alone for Fe/Mn reduction whereas formation of α-Al(FeMnCr)Si was observed when Mn and Cr both were used for the reduction of Fe and Mn from high Si alloy.

In the present study, the effect of different alloying element addition was investigated to decrease the Fe/Mn content in scrap aluminum alloy with low and high Si for an efficient aluminum recovery. In order to determine the theoretical thermodynamic guidance for efficient purification of scrap aluminum alloys, the solidification diagrams and equilibrium concentrations of alloying elements at different concentrations and temperatures within Al alloy scrap were calculated using Thermo-Calc software. The main points of consideration from these studies are as follows: Mn alone cannot reduce the Fe content from a low Si containing Al-alloy; the addition of Cr in a low Si alloy promotes the Fe-rich phase precipitation first from the liquid phase; due to less fluidity of low Si alloy at favorable temperatures for Fe/Mn rich impurity-rich intermetallic sedimentation; Cr additions improve the precipitation temperature and promote the formation of Fe/Mn-containing phase in high Si alloys; lower holding temperature enhances the growth of Fe/Mn-containing phase in high Si alloys and subsequent removal of Fe and Mn; the synergistic effect of Mn (1%) and Cr (0.8%) results in a 70% reduction in Fe/Mn in high Si alloys containing >1% Fe and Mn in 1 hr. at the holding temperature of 630° C.

Various modifications of the present disclosure, in addition to those shown and described herein, will be apparent to those skilled in the art of the above description. Such modifications are also intended to fall within the scope of the appended claims.

It is appreciated that all reagents are obtainable by sources known in the art unless otherwise specified.

It is also to be understood that this disclosure is not limited to the specific aspects and methods described herein, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing particular aspects of the present disclosure and is not intended to be limiting in any way. It will be also understood that, although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, “a first element,” “component,” “region,” “layer,” or “section” discussed below could be termed a second (or other) element, component, region, layer, or section without departing from the teachings herein. Similarly, as used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. The term “or a combination thereof” means a combination including at least one of the foregoing elements.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Reference is made in detail to exemplary compositions, aspects and methods of the present disclosure, which constitute the best modes of practicing the disclosure presently known to the inventors. The drawings are not necessarily to scale. However, it is to be understood that the disclosed aspects are merely exemplary of the disclosure that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the disclosure and/or as a representative basis for teaching one skilled in the art to variously employ the present disclosure.

Patents, publications, and applications mentioned in the specification are indicative of the levels of those skilled in the art to which the disclosure pertains. These patents, publications, and applications are incorporated herein by reference to the same extent as if each individual patent, publication, or application was specifically and individually incorporated herein by reference.

The foregoing description is illustrative of particular embodiments of the disclosure, but is not meant to be a limitation upon the practice thereof. The following claims, including all equivalents thereof, are intended to define the scope of the disclosure.

Claims

1. A process for producing an aluminum alloy comprising:

a.) melting an aluminum source at >725-° C. to obtain a melt;
b.) adding to the melt with an alloying element at at least >725° C., wherein the alloying element is selected from the group consisting of chromium, vanadium, yttrium, cerium, manganese, or at least two thereof;
c.) lowering the temperature of the melt to a lowered holding temperature of about 615° C. to about 725° C.;
d.) maintaining melt at the lowered holding temperature for at least about 15 minutes; and
e.) removing precipitated impurity-rich intermetallics from the melt to provide the aluminum alloy.

2. The process of claim 1, wherein alloying element comprises 0.3 to 5% by weight of the melt.

3. The process of claim 1, wherein the aluminum source comprises a wrought aluminum and/or a cast aluminum.

4. The process of claim 1, wherein holding the melt in step (b) is for a period of time of at least 15 minutes.

5. The process of claim 1, wherein the temperature of the melt is lowered to the lowered temperature at a cooling rate of about 5° C. to about 15° C. per minute.

6. The process of claim 1, wherein the scrap aluminum comprises an iron content of at least 0.2% by weight.

7. The process of claim 1, wherein the scrap aluminum comprises a silicon content of less than 3% by weight.

8. The process of claim 1, wherein the scrap aluminum comprises a silicon content of at least than 3% by weight.

9. The process of claim 1, wherein the alloying element comprises manganese.

10. The process of claim 1, wherein the alloying element comprises chromium.

11. The process of claim 1, wherein in the alloying element comprises cerium.

12. The process of claim 1, wherein the alloying element comprises yttrium.

13. The process of claim 1, wherein the alloying element comprises vanadium.

14. The process of claim 1, wherein the alloying element comprises magnesium and chromium.

15. The process of claim 1, further comprising raising the silicon content of the melt.

16. The process of claim 1, wherein the melt is mixed by mechanical stirring.

17. The process of claim 1, wherein the lowered holding temperature is of about 615 to about 650° C.

18. The process of claim 1, wherein the cooling rate allows for formation of iron-manganese impurity-rich intermetallics to initiate.

19. An impurity-rich intermetallic aluminum alloy comprised of aluminum, 0.01 to 10 wt. % iron, 0.01-10 wt. % manganese, and 0.2-2.0 wt. % of an alloying element selected from the group consisting of chromium, cerium, magnesium, vanadium, yttrium, manganese or a combination thereof.

20. The impurity-rich intermetallic aluminum alloy of claim 19, further comprising 0 to 12 wt. % silicon.

Patent History
Publication number: 20240167122
Type: Application
Filed: Oct 26, 2023
Publication Date: May 23, 2024
Inventors: Manish Sinha (Worcester, MA), Jessica Hiscocks (Kingston), Subodh Das (Saint Louis, MO), Boyd Davis (Kingston), Brajendra Mishra (Worcester, MA), Tom Grosko (Columbia, TN), John Pickens (Strongsville, OH)
Application Number: 18/495,280
Classifications
International Classification: C22C 1/02 (20060101);