Patent Application
20210388468
The disclosure is directed to high strength recycled aluminum alloys and processes for recycling aluminum alloy scrap with cosmetic appeal and applications including enclosures for electronic devices.
Commercial aluminum alloys, such as the 6063 aluminum (Al) alloys, have been used for fabricating enclosures for electronic devices. Cosmetic appeal is very important for enclosures for electronic devices.
Conventional recycling of manufacturing chip scrap (e.g. 6063 Al) is generally associated with downgraded quality. Sometimes, in order to maintain the quality of the recycled product, conventional recycling of manufacturing chip scrap and may be limited to a particular source and a limited amount of scrap in the recycled material.
There remains a need for developing alloys and processes for recycling manufacturing scrap to improve the strength and cosmetic appeal of the recycled aluminum alloys.
In one aspect, the disclosure provides an aluminum alloy including iron (Fe) in an amount of 0.10 wt % to 0.50 wt %; silicon (Si) in an amount of 0.50 wt % to 1.00 wt %; magnesium (Mg) in amount of 0.50 wt % to 0.90 wt %; one of manganese (Mn) or chromium (Cr) in amount from 0.040 to 0.500 wt %; additional non-aluminum (Al) elements in an amount not exceed 3.5 wt %; and the remaining wt % being Al and incidental impurities, wherein the alloy has a Mg/Si ratio of equal to or greater than 0.90.
In another aspect, a process is provided for recycling manufacturing scrap. The process may include (a) obtaining an aluminum alloy from manufacturing scrap. The aluminum alloy may include iron (Fe) in an amount of 0.10 wt % to 0.50 wt %; silicon (Si) in an amount of 0.50 wt % to 1.00 wt %; magnesium (Mg) in amount of 0.50 wt % to 0.90 wt %; one of manganese (Mn) or chromium (Cr) in amount from 0.04 to 0.50 wt %; additional non-aluminum (Al) elements in an amount not exceeding 3.5 wt %; and the remaining wt % being Al and incidental impurities. The alloy may have a Mg/Si ratio of equal to or greater than 0.90. The alloy may have a yield strength of at least 250 MPa and a tensile strength of at least 280 MPa. The process may also include (b) melting the aluminum alloy to form a melted aluminum alloy; (c) casting the melted aluminum alloy to form a casted alloy; (d) extruding or rolling the casted alloy to form an extrusion or a sheet; and (e) fabricating the extrusion or the sheet to produce a product.
In another aspect, the disclosure provides an aluminum alloy including iron (Fe) in an amount of 0.10 wt % to 0.50 wt %, silicon (Si) in an amount of 0.50 wt % to 1.00 wt %, magnesium (Mg) in amount of 0.50 wt % to 0.90 wt %, manganese (Mn) in amount of 0 to 0.30 wt %, non-aluminum (Al) elements in an amount not exceeding 3.0 wt %, the remaining wt % being Al and incidental impurities. The alloy may have a Mg/Si ratio of less than or equal to 1.0.
In another aspect, a process is provided for recycling manufacturing scrap. The process may include (a) obtaining an aluminum alloy from manufacturing scrap; (b) melting the aluminum alloy to form a melted aluminum alloy; (c) casting the melted aluminum alloy to form a casted alloy; (d) extruding or rolling the casted alloy to form an extrusion or a sheet; and (e) fabricating the extrusion or sheet to produce a product.
Additional embodiments and features are set forth in part in the description that follows, and will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the disclosed subject matter. A further understanding of the nature and advantages of the disclosure may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure.
The description will be more fully understood with reference to the following figures and data graphs, which are presented as various embodiments of the disclosure and should not be construed as a complete recitation of the scope of the disclosure, wherein:
The disclosure may be understood by reference to the following detailed description, taken in conjunction with the drawings as described below. It is noted that, for purposes of illustrative clarity, certain elements in various drawings may not be drawn to scale.
Reference Alloy 1 was a representative 6000 series alloy disclosed in U.S. patent application Ser. No. 16/530,830, entitled “Recycled Aluminum Alloys from Manufacturing Scrap with Cosmetic Appeal,” by Gable et al., filed on Aug. 2, 2019, which is incorporated by reference in its entirety. Reference Alloy 1 has similar strength as a virgin aluminum alloy 6063, which is referred to Reference Alloy 2 in the disclosure. The Reference Alloy 1 can provide the same or similar cosmetic appeal, mechanical properties, and microstructure as the virgin or primary aluminum alloy. The Reference Alloy 1 can include higher Fe content, and/or higher Si content than aluminum alloys made from primary aluminum.
This disclosure provides a recycled 6000 series aluminum alloys that utilizes manufacturing scraps for cosmetic application. The disclosed recycled aluminum alloys can achieve 30% higher tensile yield strength than Reference Alloy 1, while still achieving reasonable anodization cosmetics and without difficulty in manufacturing processes (e.g. extrusion process). Also, incorporation of 100% recycling of manufacturing scraps in Reference Alloy 1 was maintained in the disclosed alloy.
The disclosed recycled 6000 series aluminum alloys were also formed from scrap. The scrap can be collected from manufacturing processes of conventional aluminum alloys (e.g. 6000 series aluminum alloys or 6063 aluminum). The disclosed alloy can include higher Mn content, higher Si content, and higher Mg content than Reference Alloy 1.
The disclosure also provides Mn, Mg, and Si compositions to achieve properties including aspects of microstructure, color, strengths, ductility, and processability. For example, an addition of a small amount of Mn (e.g. 0.040 to 0.500 wt %) surprisingly provides increased conversion of large β-AlFeSi particles to small α-AlFeSi particles, and increased the yield strengths, tensile strengths, and elongations of alloys. Increasing Mn (e.g. 0.040 to 0.500 wt %) was also found to increase anodization color b* of the alloys. Also, increasing Mg increased the yield strengths and tensile strengths of alloys and also reduce anodization color b* of the alloys. However, increasing Mg (e.g. 0.1 wt %) can also make extrusion more difficult. Further, increasing Si (e.g. 0.2 wt %) increased the yield strengths and tensile strengths of alloys. Increasing Si was also found to reduce the ductility. Decreasing Si lowered the anodization color b* of the alloys. Decreasing Si also promotes the formation of small α-AlFeSi particles.
For the higher strength applications where a 7000 series aluminum alloy (e.g. Reference Alloy 3) was considered for possible uses, there was concern for the corrosion resistance of the 7000 series aluminum alloy. Reference Alloy 3 was a representative alloy disclosed in U.S. patent Ser. No. 15/406,153, entitled “ALUMINUM ALLOYS WITH HIGH STRENGTH AND COSMETIC APPEAL,” by Misra et al., issued on Jan. 13, 2017, which is incorporated by reference in its entirety. The disclosed alloys can provide an alternative to reduce the risk of corrosion of the 7000 series aluminum alloys. The disclosed alloy can be used for an electronic enclosure. The disclosed alloy has demonstrated 30% higher tensile yield strength than Reference Alloy 1. The disclosed alloy also revealed comparable yield strength with the 7000 series aluminum alloys, and promising microstructure and ano cosmetics. Also, the disclosed alloy revealed reasonable extrudability and was extruded at 60% higher speed than 7000 series aluminum alloys.
In some variations, the disclosed 6000 series aluminum alloys are designed to be tolerant to include up to 100% recycled 6000 series aluminum, such as casting scrap, extrusion scrap, chip scrap from manufacturing, among others. The disclosed 6000 series aluminum alloys may also be tolerant to other series scraps, such as 1000 series scrap. The disclosed 6000 series aluminum alloys allow a closed-loop of manufacturing scrap that can reduce use of virgin aluminum, and result in significant reduction of emissions and related carbon footprint. Conventional 6000 series Al can include small amounts of Si and Mg, and optionally includes small amounts of Fe, Mn, Cu, Zr, Pb, Cr, Zn, among others.
A customer 114 uses the modules from the module manufacturing 106 to build product, which may be used in field in operation 112. A recovered material 108 may be produced from the field used product. The recovered material 108 may also be provided to material processing 104.
Recycled aluminum alloys can accumulate more iron than is typically present in virgin aluminum alloys. The increase in iron can have a negative effect on the cosmetic appeal of aluminum alloys, particularly by having a more gray color. Iron cannot be removed from aluminum alloys by conventional industrial methods, and once iron is included in the aluminum alloy, the amount of iron in the alloy cannot be reduced. Because of the number of iron-containing contact points in a typical supply chain, the amount of iron can be higher in recycled aluminum than in virgin aluminum.
Iron can have negative effects on the cosmetic appeal by creating an unattractive gray color. In addition to having a negative effect on cosmetics, iron contributes to the formation of iron-aluminum-silicon particles during processing. The acquisition of Si by the iron-containing particles reduces the amount of Si available for strengthening. As such, more Si is added to the alloys disclosed herein. The presently disclosed alloys have increased silicon and increased iron. Contrary to expectations, various properties of the alloy are consistent or better than alloys with such undesirable amounts of iron.
The disclosed recycled 6000 series aluminum alloys allow use of recycled materials, such as manufacturing scrap from various sources. The disclosed recycled 6000 series aluminum alloys result in significant reduction of the carbon footprint associated with manufacturing.
The alloys can be described by various wt % of elements, as well as specific properties. In all descriptions of the alloys described herein, it will be understood that the wt % balance of alloys is Al and incidental impurities. Impurities can be present, for example, as a byproduct of processing and manufacturing. In various embodiments, an incidental impurity can be no greater than 0.05 wt % of any one additional element (i.e., a single impurity), and no greater than 0.10 wt % total of all additional elements (i.e., total impurities). The impurities can be less than or equal to about 0.1 wt %, alternatively less than or equal about 0.05 wt %, alternatively less than or equal about 0.01 wt %, alternatively less than or equal about 0.001 wt %.
In some variations, the alloy has at least 0.14 wt % Fe. Further, in some variations, the alloy has at least 0.50 wt % Si and at least 0.50 wt % Mg. In still further variations, the alloy can have equal to or less than 0.20 wt % Fe. The alloy can have equal to or less than 0.90 wt % Mg and equal to or less than 1.00 wt % Si.
As described above, the scrap (e.g., chip scrap) includes more Fe than Reference Alloy 2. The Fe may be from sources including tooling among others. The disclosed 6000 series aluminum alloy is designed to have more Fe than Reference Alloy 2 or virgin aluminum alloys currently used for cosmetic consumer electronic products.
In some variations, iron may range from 0.10 wt % to 0.50 wt %.
In some variations, iron may be equal to or greater than 0.10 wt %. In some variations, iron may be equal to or greater than 0.14 wt %. In some variations, iron may be equal to or greater than 0.15 wt %. In some variations, iron may be equal to or greater than 0.16 wt %. In some variations, iron may be equal to or greater than 0.17 wt %. In some variations, iron may be equal to or greater than 0.18 wt %. In some variations, iron may be equal to or greater than 0.19 wt %. In some variations, iron may be equal to or greater than 0.20 wt %. In some variations, iron may be equal to or greater than 0.25 wt %. In some variations, iron may be equal to or greater than 0.30 wt %. In some variations, iron may be equal to or greater than 0.35 wt %. In some variations, iron may be equal to or greater than 0.40 wt %. In some variations, iron may be equal to or greater than 0.45 wt %.
In some variations, iron may be equal to or less than 0.50 wt %. In some variations, iron may be equal to or less than 0.45 wt %. In some variations, iron may be equal to or less than 0.35 wt %. In some variations, iron may be equal to or less than 0.40 wt %. In some variations, iron may be equal to or less than 0.35 wt %. In some variations, iron may be equal to or less than 0.30 wt %. In some variations, iron may be equal to or less than 0.25 wt %. In some variations, iron may be equal to or less than 0.20 wt %. In some variations, iron may be equal to or less than 0.19 wt %. In some variations, iron may be equal to or less than 0.18 wt %. In some variations, iron may be equal to or less than 0.17 wt %. In some variations, iron may be equal to or less than 0.16 wt %. In some variations, iron may be equal to or less than 0.15 wt %.
Scrap can include more Ti than the conventional 6000 series aluminum alloys. The Ti can be added as a grain refiner during casting process. In many instances, the 6000 series aluminum alloy is designed to tolerate more Ti versus conventional aluminum alloys used for similar products.
In some variations, titanium may equal to or less than 0.10 wt %. In some variations, titanium may equal to or less than 0.09 wt %. In some variations, titanium may equal to or less than 0.08 wt %. In some variations, titanium may equal to or less than 0.07 wt %. In some variations, titanium may equal to or less than 0.06 wt %. In some variations, titanium may equal to or less than 0.05 wt %. In some variations, titanium may equal to or less than 0.04 wt %. In some variations, titanium may equal to or less than 0.03 wt %. In some variations, titanium may equal to or less than 0.025 wt %. In some variations, titanium may be equal to or less than 0.020 wt %. In some variations, titanium may be equal to or less than 0.015 wt %. In some variations, titanium may be equal to or less than 0.010 wt %. In some variations, titanium may be equal to or less than 0.005 wt %.
Comparing to Reference Alloy 1 and Reference Alloy 2, the alloy is more Si rich and forms more precipitates MgxSiy, which provides the alloy with higher strength. However, the MgxSiy precipitates also potentially affect cosmetic appeal and color due to the formation of surface features. Reducing Si reduces the color b* of the anodized alloy.
In some variations, silicon may vary from 0.50 wt % to 1.00 wt %.
In some variations, silicon may be equal to or less than 1.00 wt %. In some variations, silicon may be equal to or less than 0.95 wt %. In some variations, silicon may be equal to or less than 0.90 wt %. In some variations, silicon may be equal to or less than 0.85 wt %. In some variations, silicon may be equal to or less than 0.80 wt %. In some variations, silicon may be equal to or less than 0.75 wt %. In some variations, silicon may be equal to or less than 0.70 wt %. In some variations, silicon may be equal to or less than 0.65 wt %. In some variations, silicon may be equal to or less than 0.60 wt %. In some variations, silicon may be equal to or less than 0.55 wt %.
In some variations, silicon may be equal to or greater than 0.50 wt %. In some variations, silicon may be equal to or greater than 0.55 wt %. In some variations, silicon may be equal to or greater than 0.60 wt %. In some variations, silicon may be equal to or greater than 0.65 wt %. In some variations, silicon may be equal to or greater than 0.70 wt %. In some variations, silicon may be equal to or greater than 0.75 wt %. In some variations, silicon may be equal to or greater than 0.80 wt %. In some variations, silicon may be equal to or greater than 0.85 wt %. In some variations, silicon may be equal to or greater than 0.90 wt %. In some variations, silicon may be equal to or greater than 0.95 wt %.
Mg can be designed to have the proper Mg/Si ratio to form Mg—Si precipitates for strengthening purpose. However, higher Mg content can make extrusion harder. Increasing Mg reduces color b* of the anodized alloy.
In some variations, magnesium may vary from 0.50 wt % to 0.95 wt %.
In some variations, magnesium may be equal to or less than 0.95 wt %. In some variations, magnesium may be equal to or less than 0.90 wt %. In some variations, magnesium may be equal to or less than 0.85 wt %, In some variations, magnesium may be equal to or less than 0.80 wt %. In some variations, magnesium may be equal to or less than 0.75 wt %. In some variations, magnesium may be equal to or less than 0.70 wt %. In some variations, magnesium may be equal to or less than 0.65 wt %. In some variations, magnesium may be equal to or less than 0.60 wt %. In some variations, magnesium may be equal to or less than 0.55 wt %. In some variations, magnesium may be equal to or greater than 0.50 wt %. In some variations, magnesium may be equal to or greater than 0.55 wt %. In some variations, magnesium may be equal to or greater than 0.60 wt %. In some variations, magnesium may be equal to or greater than 0.65 wt %. In some variations, magnesium may be equal to or greater than 0.70 wt %. In some variations, magnesium may be equal to or greater than 0.75 wt %. In some variations, magnesium may be equal to or greater than 0.85 wt %. In some variations, magnesium may be equal to or greater than 0.90 wt %.
The alloy 6063 or Reference Alloy 2 includes a typical precipitate of Mg2Si, which would require a Si/Mg ratio of 0.8 or Mg/Si ratio of 1.25. The Reference Alloy 1 has a Mg/Si ratio greater than 1. However, the disclosed alloy can have a Mg/Si ratio lower than the Mg/Si ratio of Reference Alloy 1, and forms various precipitates MgxSiy.
In some variations, the ratio of Mg to Si (Mg/Si) varies from 0.60 to 1.8.
In some variations, the ratio of Mg to Si may be equal to or greater than 0.60. In some variations, the ratio of Mg to Si may be equal to or greater than 0.65. In some variations, the ratio of Mg to Si may be equal to or greater than 0.70. In some variations, the ratio of Mg to Si may be equal to or greater than 0.75. In some variations, the ratio of Mg to Si may be equal to or greater than 0.80. In some variations, the ratio of Mg to Si may be equal to or greater than 0.85. In some variations, the ratio of Mg to Si may be equal to or greater than 0.90. In some variations, the ratio of Mg to Si may be equal to or greater than 0.95. In some variations, the ratio of Mg to Si may be equal to or greater than 1.00. In some variations, the ratio of Mg to Si may be equal to or greater than 1.05. In some variations, the ratio of Mg to Si may be equal to or greater than 1.10. In some variations, the ratio of Mg to Si may be equal to or greater than 1.15. In some variations, the ratio of Mg to Si may be equal to or greater than 1.20. In some variations, the ratio of Mg to Si may be equal to or greater than 1.25. In some variations, the ratio of Mg to Si may be equal to or greater than 1.30. In some variations, the ratio of Mg to Si may be equal to or greater than 1.40. In some variations, the ratio of Mg to Si may be equal to or greater than 1.50. In some variations, the ratio of Mg to Si may be equal to or greater than 1.70.
In some variations, the ratio of Mg to Si may be less than or equal to 0.65. In some variations, the ratio of Mg to Si may be less than or equal to 0.70. In some variations, the ratio of Mg to Si may be less than or equal to 0.75. In some variations, the ratio of Mg to Si may be less than or equal to 0.80. In some variations, the ratio of Mg to Si may be less than or equal to 0.85. In some variations, the ratio of Mg to Si may be less than or equal to 0.90. In some variations, the ratio of Mg to Si may be less than or equal to 0.95. In some variations, the ratio of Mg to Si may be less than or equal to 1.00. In some variations, the ratio of Mg to Si may be less than or equal to 1.05. In some variations, the ratio of Mg to Si may be less than or equal to 1.10. In some variations, the ratio of Mg to Si may be less than or equal to 1.15. In some variations, the ratio of Mg to Si may be less than or equal to 1.20. In some variations, the ratio of Mg to Si may be less than or equal to 1.25. In some variations, the ratio of Mg to Si may be less than or equal to 1.30. In some variations, the ratio of Mg to Si may be less than or equal to 1.40. In some variations, the ratio of Mg to Si may be less than or equal to 1.50. In some variations, the ratio of Mg to Si may be less than or equal to 1.60. In some variations, the ratio of Mg to Si may be less than or equal to 1.70. In some variations, the ratio of Mg to Si may be less than or equal to 1.80.
In some variations, the alloy can include Mn. Without wishing to be held to a particular mechanism, effect, or mode of action, Mn can help break up the coarse Al—Fe—Si particles or AlFeSi particles that form during casting. Mn can be added to break up large contaminant Al—Fe—Si particles and to form smaller Al—Fe—Si particles. The large Al—Fe—Si particles are also referred to β-AlFeSi particles, while the smaller Al—Fe—Si and Al—Fe—Mn—Si particles are also referred to α-AlFe(Mn)Si particles. Increasing Mn (e.g. 0.040 to 0.500 wt %) was also found to increase anodization color b* value with addition of Mn.
In some variations, manganese may be equal to or less than 0.500 wt %. In some variations, manganese may be equal to or less than 0.450 wt %. In some variations, manganese may be equal to or less than 0.400 wt %. In some variations, manganese may be equal to or less than 0.350 wt %. In some variations, manganese may be equal to or less than 0.300 wt %. In some variations, manganese may be equal to or less than 0.250 wt %. In some variations, manganese may be equal to or less than 0.200 wt %. In some variations, manganese may be equal to or less than 0.190 wt %. In some variations, manganese may be equal to or less than 0.180 wt %. In some variations, manganese may be equal to or less than 0.170 wt %. In some variations, manganese may be equal to or less than 0.160 wt %. In some variations, manganese may be equal to or less than 0.150 wt %. In some variations, manganese may be equal to or less than 0.140 wt %. In some variations, manganese may be equal to or less than 0.130 wt %. In some variations, manganese may be equal to or less than 0.120 wt %. In some variations, manganese may be equal to or less than 0.110 wt %. In some variations, manganese may be equal to or less than 0.100 wt %. In some variations, manganese may be equal to or less than 0.095 wt %. In some variations, manganese may be equal to or less than 0.090 wt %. In some variations, manganese may be equal to or less than 0.050 wt %. In some variations, manganese may be equal to or less than 0.010 wt %. In some variations, manganese may be equal to or less than 0.005 wt %.
In some variations, manganese may be equal to or greater than 0 wt %. In some variations, manganese may be equal to or greater than 0.005 wt %. In some variations, manganese may be equal to or greater than 0.010 wt %. In some variations, manganese may be equal to or greater than 0.040 wt %. In some variations, manganese may be equal to or greater than 0.050 wt %. In some variations, manganese may be equal to or greater than 0.090 wt %. In some variations, manganese may be equal to or greater than 0.095 wt %. In some variations, manganese may be equal to or greater than 0.100 wt %. In some variations, manganese may be equal to or greater than 0.110 wt %. In some variations, manganese may be equal to or greater than 0.120 wt %. In some variations, manganese may be equal to or greater than 0.130 wt %. In some variations, manganese may be equal to or greater than 0.140 wt %. In some variations, manganese may be equal to or greater than 0.150 wt %. In some variations, manganese may be equal to or greater than 0.160 wt %. In some variations, manganese may be equal to or greater than 0.170 wt %. In some variations, manganese may be equal to or greater than 0.180 wt %. In some variations, manganese may be equal to or greater than 0.190 wt %. In some variations, manganese may be equal to or greater than 0.200 wt %. In some variations, manganese may be equal to or greater than 0.250 wt %. In some variations, manganese may be equal to or greater than 0.300 wt %. In some variations, manganese may be equal to or greater than 0.350 wt %. In some variations, manganese may be equal to or greater than 0.400 wt %. In some variations, manganese may be equal to or greater than 0.450 wt %.
Chromium may have similar function to Mn. In some embodiment, the alloy may include Cr in an amount of 0.040 wt % to 0.500 wt % to replace Mn. In some embodiment, the alloy may have a combination of Mn and Cr in an amount of 0.040 wt % to 0.800 wt %.
In some embodiments, a combination of Mn and Cr may be equal to or less than 0.800 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.750 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.700 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.650 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.600 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.550 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.500 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.450 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.400 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.350 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.300 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.250 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.200 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.150 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.100 wt %. In some embodiments, a combination of Mn and Cr may be equal to or less than 0.050 wt %.
In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.750 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.700 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.650 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.600 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.550 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.500 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.450 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.400 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.350 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.300 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.250 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.200 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.150 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.100 wt %. In some embodiments, a combination of Mn and Cr may be equal to or greater than 0.040 wt %.
In some variations, chromium may be equal to or less than 0.500 wt %. In some variations, chromium may be equal to or less than 0.450 wt %. In some variations, chromium may be equal to or less than 0.400 wt %. In some variations, chromium may be equal to or less than 0.350 wt %. In some variations, chromium may be equal to or less than 0.300 wt %. In some variations, chromium may be equal to or less than 0.250 wt %. In some variations, chromium may be equal to or less than 0.200 wt %. In some variations, chromium may be equal to or less than 0.190 wt %. In some variations, chromium may be equal to or less than 0.180 wt %. In some variations, chromium may be equal to or less than 0.170 wt %. In some variations, chromium may be equal to or less than 0.160 wt %. In some variations, chromium may be equal to or less than 0.150 wt %. In some variations, chromium may be equal to or less than 0.140 wt %. In some variations, chromium may be equal to or less than 0.130 wt %. In some variations, chromium may be equal to or less than 0.120 wt %. In some variations, chromium may be equal to or less than 0.110 wt %. In some variations, chromium may be equal to or less than 0.100 wt %. In some variations, chromium may be equal to or less than 0.095 wt %. In some variations, chromium may be equal to or less than 0.090 wt %. In some variations, chromium may be equal to or less than 0.050 wt %. In some variations, chromium may be equal to or less than 0.010 wt %. In some variations, chromium may be equal to or less than 0.005 wt %.
In some variations, chromium may be equal to or greater than 0 wt %. In some variations, chromium may be equal to or greater than 0.005 wt %. In some variations, chromium may be equal to or greater than 0.010 wt %. In some variations, chromium may be equal to or greater than 0.040 wt %. In some variations, chromium may be equal to or greater than 0.050 wt %. In some variations, chromium may be equal to or greater than 0.090 wt %. In some variations, chromium may be equal to or greater than 0.095 wt %. In some variations, chromium may be equal to or greater than 0.100 wt %. In some variations, chromium may be equal to or greater than 0.110 wt %. In some variations, chromium may be equal to or greater than 0.120 wt %. In some variations, chromium may be equal to or greater than 0.130 wt %. In some variations, chromium may be equal to or greater than 0.140 wt %. In some variations, chromium may be equal to or greater than 0.150 wt %. In some variations, chromium may be equal to or greater than 0.160 wt %. In some variations, chromium may be equal to or greater than 0.170 wt %. In some variations, chromium may be equal to or greater than 0.180 wt %. In some variations, chromium may be equal to or greater than 0.190 wt %. In some variations, chromium may be equal to or greater than 0.200 wt %. In some variations, chromium may be equal to or greater than 0.250 wt %. In some variations, chromium may be equal to or greater than 0.300 wt %. In some variations, chromium may be equal to or greater than 0.350 wt %. In some variations, chromium may be equal to or greater than 0.400 wt %. In some variations, chromium may be equal to or greater than 0.450 wt %.
The disclosed 6000 series aluminum alloy may include other elements as disclosed below.
In some variations, the alloy can include Cu. Without wishing to be limited to any particular mechanism, effect, or mode of action, Cu can improve corrosion resistance, and/or Cu can influence color of the anodized alloy.
In some variations, copper may vary from 0.010 wt % to 0.050 wt %.
In some variations, copper may be equal to or less than 0.050 wt %. In some variations, copper may be equal to or less than 0.045 wt %. In some variations, copper may be equal to or less than 0.040 wt %. In some variations, copper may be equal to or less than 0.035 wt %. In some variations, copper may be equal to or less than 0.030 wt %. In some variations, copper may be equal to or less than 0.025 wt %. In some variations, copper may be equal to or less than 0.020 wt %. In some variations, copper may be equal to or less than 0.015 wt %.
In some variations, copper may be equal to or greater than 0.010 wt %. In some variations, copper may be equal to or greater than 0.015 wt %. In some variations, copper may be equal to or greater than 0.020 wt %. In some variations, copper may be equal to or greater than 0.025 wt %. In some variations, copper may be equal to or greater than 0.030 wt %. In some variations, copper may be equal to or greater than 0.035 wt %. In some variations, copper may be equal to or greater than 0.040 wt %. In some variations, copper may be equal to or greater than 0.045 wt %.
In some variations, chromium may be equal to or less than 0.10 wt %. In some variations, chromium may be equal to or less than 0.08 wt %. In some variations, chromium may be equal to or less than 0.06 wt %. In some variations, chromium may be equal to or less than 0.04 wt %. In some variations, chromium may be equal to or less than 0.03 wt %. In some variations, chromium may be equal to or less than 0.02 wt %. In some variations, chromium may be equal to or less than 0.01 wt %. In some variations, chromium may be equal to or less than 0.008 wt %. In some variations, chromium may be equal to or less than 0.006 wt %. In some variations, chromium may be equal to or less than 0.004 wt %. In some variations, chromium may be equal to or less than 0.002 wt %.
In some variations, zinc may be equal to or less than 0.20 wt %. In some variations, zinc may be equal to or less than 0.15 wt %. In some variations, zinc may be equal to or less than 0.10 wt %. In some variations, zinc may be equal to or less than 0.08 wt %. In some variations, zinc may be equal to or less than 0.06 wt %. In some variations, zinc may be equal to or less than 0.04 wt %. In some variations, zinc may be equal to or less than 0.03 wt %. In some variations, zinc may be equal to or less than 0.02 wt %. In some variations, zinc may be equal to or less than 0.01 wt %. In some variations, zinc may be equal to or less than 0.005 wt %. In some variations, zinc may be equal to or less than 0.001 wt %.
In some variations, gallium may be equal to or less than 0.20 wt %. In some variations, gallium may be equal to or less than 0.15 wt %. In some variations, gallium may be equal to or less than 0.10 wt %. In some variations, gallium may be equal to or less than 0.08 wt %. In some variations, gallium may be equal to or less than 0.06 wt %. In some variations, gallium may be equal to or less than 0.04 wt %. In some variations, gallium may be equal to or less than 0.03 wt %. In some variations, gallium may be equal to or less than 0.02 wt %. In some variations, gallium may be equal to or less than 0.015 wt %. In some variations, gallium may be equal to or less than 0.01 wt %. In some variations, gallium may be equal to or less than 0.005 wt %. In some variations, gallium may be equal to or less than 0.001 wt %.
In some variations, tin may be equal to or less than 0.20 wt %. In some variations, tin may be equal to or less than 0.15 wt %. In some variations, tin may be equal to or less than 0.10 wt %. In some variations, tin may be equal to or less than 0.08 wt %. In some variations, tin may be equal to or less than 0.06 wt %. In some variations, tin may be equal to or less than 0.04 wt %. In some variations, tin may be equal to or less than 0.01 wt %. In some variations, tin may be equal to or less than 0.008 wt %. In some variations, tin may be equal to or less than 0.006 wt %. In some variations, tin may be equal to or less than 0.004 wt %. In some variations, tin may be equal to or less than 0.002 wt %.
In some variations, vanadium may be equal to or less than 0.20 wt %. In some variations, vanadium may be equal to or less than 0.15 wt %. In some variations, vanadium may be equal to or less than 0.10 wt %. In some variations, vanadium may be equal to or less than 0.08 wt %. In some variations, vanadium may be equal to or less than 0.06 wt %. In some variations, vanadium may be equal to or less than 0.04 wt %. In some variations, vanadium may be equal to or less than 0.02 wt %. In some variations, vanadium may be equal to or less than 0.01 wt %. In some variations, vanadium may be equal to or less than 0.005 wt %. In some variations, vanadium may be equal to or less than 0.001 wt %.
In some variations, calcium may be equal to or less than 0.001 wt %. In some variations, calcium may be equal to or less than 0.0003 wt %. In some variations, calcium may be equal to or less than 0.0002 wt %. In some variations, calcium may be equal to or less than 0.0001 wt %.
In some variations, sodium may be equal to or less than 0.002 wt %. In some variations, sodium may be equal to or less than 0.0002 wt %. In some variations, sodium may be equal to or less than 0.0001 wt %.
One or more of other elements, including chromium, boron, zirconium, lithium, cadmium, lead, nickel, phosphorous, among others, may be equal to or less than 0.01 wt %. One or more of other elements, including chromium, boron, zirconium, lithium, cadmium, lead, nickel, phosphorous, among others, may be equal to or less than 0.008 wt %. One or more of these other elements may be equal to or less than 0.006 wt %. One or more of these other elements may be equal to or less than 0.004 wt %. One or more of other elements may be equal to or less than 0.002 wt %.
In some variations, a total of other elements may not exceed 0.20 wt %. In some variations, a total of other elements may not exceed 0.10 wt %. In some variations, a total of other elements may not exceed 0.08 wt %. In some variations, a total of other elements may not exceed 0.06 wt %. In some variations, a total of other elements may not exceed 0.04 wt %.
In some variations, a total of non-aluminum elements may not exceed 3.5 wt %. In some variations, a total of non-aluminum elements may not exceed 3.0 wt %. In some variations, a total of non-aluminum elements may not exceed 2.5 wt %. In some variations, a total of non-aluminum elements may not exceed 2.0 wt %. In some variations, a total of non-aluminum elements may not exceed 1.5 wt %. In some variations, a total of non-aluminum elements may not exceed 1.0 wt %. In some variations, a total of non-aluminum elements may not exceed 0.5 wt %.
Process for Cleaning and Removing Oxides from Scrap
Scrap can have a large surface area/volume ratio compared to alloys made from virgin material. The large surface area of the scrap can include a substantial quantity of oxides, such as aluminum oxides. Scrap may also include impurities, such as Fe or Ti, among others, compared to conventional 6000 series aluminum alloys, 1000 series alloys, or virgin alloys of the 6000 series aluminum alloys.
The cleaning process may include removing oxides by re-melting scrap and flowing oxides and skim off the oxides. The cleaning process may also include removing organic contaminants by chemical solvent or solution or heating.
The disclosed recycled 6000 series aluminum alloys can be made from up to 100% Al scrap, and can be used to form a part by extrusion. The disclosed recycled 6000 series aluminum alloys can also include scrap extrusion or sheet material. The disclosed methods can include or exclude primary aluminum or virgin aluminum.
In some embodiments, a melt for an alloy can be prepared by heating the alloy including the composition.
The melted scrap may be billet or slab casted to form an extrusion at operation 206, and then homogenized. In some embodiments, the cast alloys can be homogenized by heating to an elevated temperature and holding at the elevated temperature for a period of time, such as at an elevated temperature of 520° C. to 620° C. for a period of time, e.g. 8-18 hours.
As shown in
The homogenized alloy may be extruded or rolled at operation 208. Extrusion is a process for converting a metal billet into lengths of uniform cross section by forcing the metal to flow plastically through a die orifice.
A product, such as a component of part, may be fabricated from the extruded or rolled aluminum alloy obtained at operation 210.
In some embodiments, the extruded alloys can be preheated to an elevated temperature, e.g. about 400° C. and ramped up to a higher temperature, e.g. above 500° C. for extrusion. The extrusion and solution heat-treatment may occur simultaneously at the higher elevated temperature, e.g. about 500° C. The solution heat treatments can alter the strength of the alloy.
In some embodiments, the chip source or scrap may also include a portion of disclosed 6000 series aluminum alloys in addition to the scrap from various sources.
After the solution treatment, the alloy can be aged at a temperature of 125 to 225° C. for about a period of time, e.g. 6-10 hours, and then quenched with water. Aging is a heat treatment at an elevated temperature, and may induce a precipitation reaction to form precipitates Mg—Si. It will be appreciated by those skilled in the art that the heat treatment condition (e.g. temperature and time) may vary.
In further embodiments, the disclosed 6000 series aluminum alloys may be optionally subjected to a stress-relief treatment between the solution heat-treatment and the aging heat-treatment. The stress-relief treatment can include stretching the alloy, compressing the alloy, or combinations thereof.
The aluminum alloys disclosed herein typically have more Fe than in conventional aluminum alloys. Aluminum alloys having higher amounts of iron particularly by having a more gray color. The scrap can include more Fe than the conventional 6000 series aluminum alloys, or Reference Alloy 2. As described above, the recycled aluminum alloys described herein have more iron than that is typically present in virgin aluminum alloys for alloys with cosmetic appeal.
Iron can have negative effects on the cosmetic appeal by creating an unattractive gray color. In addition to having a negative effect on cosmetics, iron contributes to the formation of iron-aluminum-silicon particles during processing. The acquisition of Si by the Fe particles reduces the amount of Si available for strengthening. As such, more Si is added to the alloys disclosed herein. The presently disclosed alloys also have increased silicon and increased magnesium to form more MgxSiy particles for strengthening purpose, compared to Reference Alloys 1 and 2.
In some embodiments, the disclosed 6000 series aluminum alloys can be anodized. Anodizing is a surface treatment process for metal, most commonly used to protect aluminum alloys. Anodizing uses electrolytic passivation to increase the thickness of the natural oxide layer on the surface of metal parts. Anodizing may increase corrosion resistance and wear resistance, and may also provide better adhesion for paint primers and glues than bare metal. Anodized films may also be used for cosmetic effects, for example, it may add interference effects to reflected light.
Surprisingly, the disclosed recycled 6000 series aluminum alloys have higher Si content than Reference Alloy 1, yet still the same or improved cosmetic appeal as those with lower iron, silicon, and magnesium. In particular, after anodizing they do not take a yellowish or gray color, and do not have increased cosmetic defects such as mottling, grain lines, black lines, discoloration, white dots, oxidation, and line mark, among others.
In some embodiments, the disclosed 6000 series aluminum alloys can form enclosures for electronic devices. The enclosures may be designed to have a blasted surface finish absent of streaky lines. Blasting is a surface finishing process, for example, smoothing a rough surface or roughening a smooth surface. Blasting may remove surface material by forcibly propelling a stream of abrasive media against a surface under high pressure.
Standard methods may be used for evaluation of cosmetics including color, gloss and haze. The color of objects may be determined by the wavelength of light that is reflected or transmitted without being absorbed, assuming incident light is white light. The visual appearance of objects may vary with light reflection or transmission. Additional appearance attributes may be based on the directional brightness distribution of reflected light or transmitted light, commonly referred to as glossy, shiny, dull, clear, hazy, among others. The quantitative evaluation may be performed based on ASTM Standards on Color & Appearance Measurement or ASTM E-430 Standard Test Methods for Measurement of Gloss of High-Gloss Surfaces, including ASTM D523 (Gloss), ASTM D2457 (Gloss on plastics), ASTM E430 (Gloss on high-gloss surfaces, haze), and ASTM D5767 (DOI), among others. The measurements of gloss, haze, and DOI may be performed by testing equipment, such as Rhopoint IQ.
In some embodiments, color may be quantified by parameters L*, a*, and b*, where L* stands for light brightness, a* stands for color between red and green, and b* stands for color between blue and yellow. For example, high b* values suggest an unappealing yellowish color, not a gold yellow color. Nearly zero parameters a* and b* suggest a neutral color. Low L* values suggest dark brightness, while high L* value suggests great brightness. For color measurement, testing equipment, such as X-Rite ColorEye XTH, X-Rite Coloreye 7000 may be used. These measurements are according to CIE/ISO standards for illuminants, observers, and the L*, a*, and b* color scale. For example, the standards include: (a) ISO 11664-1:2007(E)/CIE S 014-1/E:2006: Joint ISO/CIE Standard: Colorimetry—Part 1: CIE Standard Colorimetric Observers; (b) ISO 11664-2:2007(E)/CIE S 014-2/E:2006: Joint ISO/CIE Standard: Colorimetry—Part 2: CIE Standard Illuminants for Colorimetry, (c) ISO 11664-3:2012(E)/CIE S 014-3/E:2011: Joint ISO/CIE Standard: Colorimetry—Part 3: CIE Tristimulus Values; and (d) ISO 11664-4:2008(E)/CIE S 014-4/E:2007: Joint ISO/CIE Standard: Colorimetry—Part 4: CIE 1976 L*, a*, and b* Color Space.
In some variations, L* is from 70 to 100. In some variations, L* is at least 70. In some variations, L* is at least 75. In some variations, L* is at least 80. In some variations, L* is at least 85. In some variations, L* is at least 90. In some variations, L* is at least 95. In some variations, L* is less than or equal to 100. In some variations, L* is less than or equal to 95. In some variations, L* is less than or equal to 90. In some variations, L* is less than or equal to 85. In some variations, L* is less than or equal to 80. In some variations, L* is less than or equal to 75.
In some variations, a* is from −2 to 2. In some variations, a* is at least −2. In some variations, a* is at least −1.5. In some variations, a* is at least −1.0. In some variations, a* is at least −0.5. In some variations, a* is at least 0.0. In some variations, a* is at least 0.5. In some variations, a* is at least −0.5. In some variations, a* is at least 1.0. In some variations, a* is at least 1.5. In some variations, a* is less than or equal to 2.0. In some variations, a* is less than or equal to 1.5. In some variations, a* is less than or equal to 1.0. In some variations, a* is less than or equal to 0.5. In some variations, a* is less than or equal to 0.0. In some variations, a* is less than or equal to 2.0. In some variations, a* is less than or equal to −0.5. In some variations, a* is less than or equal to −1.0. In some variations, a* is less than or equal to −1.5.
In some variations, b* is from −2 to 2. In some variations, b* is at least −2. In some variations, b* is at least −1.5. In some variations, a is at least −1.0. In some variations, b* is at least −0.5. In some variations, b* is at least 0.0. In some variations, b* is at least 0.5. In some variations, b* is at least −0.5. In some variations, b* is at least 1.0. In some variations, b* is at least 1.5. In some variations, b* is less than or equal to 2.0. In some variations, b* is less than or equal to 1.5. In some variations, b* is less than or equal to 1.0. In some variations, b* is less than or equal to 0.5. In some variations, b* is less than or equal to 0.0. In some variations, b* is less than or equal to 2.0. In some variations, b* is less than or equal to −0.5. In some variations, b* is less than or equal to −1.0. In some variations, b* is less than or equal to −1.5.
Yield strengths of the alloys may be determined via ASTM 8557, which covers the testing apparatus, test specimens, and testing procedure for tensile testing.
The 6000 series aluminum alloy can be extruded or rolled with the conventional process for aluminum alloys to have the mechanical properties, including yield strength, tensile strength, elongation, and hardness, to be the same as the aluminum alloy without any scrap.
The mechanical properties have an upper limit, which allows the alloy to be formed with dimensional consistency. The disclosed recycled 6000 series aluminum alloys can exceed the tensile strength and hardness upper limit of other cosmetic aluminum alloys. However, the range of the tensile strength and hardness remains unchanged, i.e. within the range between lower limit and upper limit. The unchanged range allows the dimension consistency during forming process, such as extrusion.
In some variations, the alloy has a yield strength of at least 270 MPa. In some variations, the alloy has a yield strength of at least 280 MPa. In some variations, the alloy has a yield strength of at least 290 MPa. In some variations, the alloy has a yield strength of at least 300 MPa. In some variations, the alloy has a yield strength of at least 310 MPa. In some variations, the alloy has a yield strength of at least 320 MPa.
In some variations, the alloy has a tensile strength of at least 300 MPa. In some variations, the alloy has a tensile strength of at least 310 MPa. In some variations, the alloy has a tensile strength of at least 320 MPa. In some variations, the alloy has a tensile strength of at least 330 MPa. In some variations, the alloy has a tensile strength of at least 340 MPa.
In some variations, the alloy has an elongation from 8% to 16%.
In some variations, the alloy has an elongation less than or equal to 16%. In some variations, the alloy has an elongation less than or equal to 14%. In some variations, the alloy has an elongation less than or equal to 12%. In some variations, the alloy has an elongation less than or equal to 10%.
In some variations, the alloy has an elongation equal to or greater than 8%. In some variations, the alloy has an elongation equal to or greater than 10%. In some variations, the alloy has an elongation equal to or greater than 12%. In some variations, the alloy has an elongation equal to or greater than 14%.
Dimensional Consistency from Part to Part
The dimensional consistency from part to part is evaluated for disclosed alloys.
Results indicate that the dimensional consistency of the disclosed alloys all match or exceed the dimensional consistency of the primary or virgin aluminum alloys, regardless of the sources for the scrap, or Reference Alloys 1 and 2.
The disclosed 6000 series aluminum alloys can also have a thermal conductivity of at least 180 W/mK, which helps heat dissipation of the electronic devices. In various embodiments, the thermal conductivity of the recycled alloys can be at least 190 W/mK. In various embodiments, the thermal conductivity of the recycled alloys can be at least 200 W/mK. In various embodiments, the thermal conductivity of the recycled alloys can be at least 210 W/mK. In various embodiments, the thermal conductivity of the recycled alloys can be at least 220 W/mK. The thermal conductivity varies with alloy composition and thermal heat treatment. The thermal conductivity measured for the disclosed alloys range from 180 to 230 W/mK.
In various embodiments, the thermal conductivity of the recycled alloys can be equal to or greater than 165 W/mK. In various embodiments, the thermal conductivity of the recycled alloys can be equal to or greater than 175 W/mK. In various embodiments, the thermal conductivity of the recycled alloys can be equal to or greater than 185 W/mK. In various embodiments, the thermal conductivity of the recycled alloys can be equal to or greater than 195 W/mK.
In various embodiments, the thermal conductivity of the recycled alloys can be equal to and less than 200 W/mK. In various embodiments, the thermal conductivity of the recycled alloys can be equal to and less than 190 W/mK. In various embodiments, the thermal conductivity of the recycled alloys can be equal to and less than 180 W/mK. In various embodiments, the thermal conductivity of the recycled alloys can be equal to and less than 170 W/mK.
Microstructure can be characterized by average grain size, largest grain size, and grain aspect ratio. The microstructure related to the mechanical properties, such as yield strength, tensile strength, and elongation among others.
The following examples are for illustration purposes only. It will be apparent to those skilled in the art that many modifications, both to materials and methods, may be practiced without departing from the scope of the disclosure.
Table 1 lists the compositions for Alloys 1-7 with different elemental compositions of disclosed recycled aluminum alloy. Alloys 1-7 were formed from manufacturing scrap. Table 1 lists the composition in wt %. Alloys 1-7 have various combinations of Mg and Si as well as Mg/Si ratios. Alloys 1-7 had higher amounts of Si and Mg than Reference Alloy 1. Alloys 1-7 had the same amounts of Fe and Cu as Reference Alloy 1. Alloys 1-4 and 7 had the same amounts of Mn as Reference Alloy 1, but Alloys 5-6 had Mn contents from 0.19 wt % to 0.21 wt %, which was much higher than Alloys 1-4 and 7. Mn can help break up the coarse Al—Fe—Si particles or AlFeSi particles that form during casting. However, Mn can increase the anodization b* color.
Table 2 lists the compositions of Reference Alloy 2, Reference Alloy 1, disclosed alloy, and Reference Alloy 3. The Reference Alloy 2 was a primary or virgin aluminum alloy, which was not recycled. The Reference Alloy 1 was cosmetic aluminum alloy, which was disclosed in U.S. patent application Ser. No. 16/530,830, entitled “Recycled Aluminum Alloys From Manufacturing Scrap with Cosmetic Appeal,” filed on Aug. 2, 2019, which is incorporated by reference in its entirety.
As shown in Table 2, Reference Alloy 2 includes a typical precipitate of Mg2Si, which would require a Si/Mg ratio of 0.5 or Mg/Si ratio of 2. Reference Alloy 1 has a Mg/Si ratio greater than 1. However, the disclosed alloy (E.g. Alloys 2-3 and 5-7) has a Mg/Si ratio of 0.60 to 1.0, which is lower than the Mg/Si ratio of Reference Alloy 1.
Alloys 1 and 4 had higher Mg and/or Si than other Alloys 2-3 and 5-7, and were found to be more challenges with processing, such as extrusion, or cosmetic appeal, and were deselected for further experiments. For example, Sample 4 had Si from 0.97 wt % to 1.03 wt %, which affected the cosmetic appeal. Sample 1 had Mg from 0.82 wt % to 0.88 wt %, which affected the extrusion. Combination of higher Mg or Si in Alloys 1 and 4 results in higher stability of Mg2Si phase than other alloys, making them more challenging to process including homogenization and extrusion. Alloys 2, 3, 5, 6, and 7 were selected for further prototypes and experiments.
The data of mechanical properties and microstructure corresponding to different preparations were presented in box plots, as shown in
The extrusion speed of the disclosed alloy was normalized against Reference Alloy 3. As shown in
In some variations, the alloy may have an extrusion speed of at least 20% higher than 7000 series alloys. In some variations, the alloy may have an extrusion speed of at least 30% higher than 7000 series alloys. In some variations, the alloy may have an extrusion speed of at least 40% higher than 7000 series alloys. In some variations, the alloy may have an extrusion speed of at least 50% higher than 7000 series alloys. In some variations, the alloy may have an extrusion speed of at least 60% higher than 7000 series alloys.
Microstructure can be characterized by average grain size, largest grain size, and grain aspect ratio.
As shown in
As shown in
Also, Alloy 5 had slightly higher yield strength and lower elongation than Alloy 2. Alloy 5 only had more Mn than Alloy 2, while Si and Mg of Alloy 5 remained the same as Alloy 2. Alloy 5 has an average yield strength slightly higher than Alloy 2, which was also likely caused by the addition of Mn.
Turning to anodization color b* now, as shown in
Alloy 7 had the desirable anodization color b*, but did not have the ano cosmetic appeal as desired due to the presence of undesirable large AlFeSi particles. Further experiments were performed in alloys varying compositions in Mg, Mn, and Si. Specifically, Mg content and Mn content were increased and Si was lowered to determine if the cosmetic appeal can be improved to meet the desired performance while the alloys can still be processable. Higher Mg/Si ratio was observed to lower the anodization color b*. In some variations, Alloys 8-11 had higher Mg/Si ratios, increasing extrusion time.
Alloy 1 was found to be more difficult to extrude than Alloys 2-7 due to slightly higher Mg amount than Alloys 2-7. Some extrusion process variations were made to extrude Alloy 1. Adjustment of extrusion parameters including speed and temperature is necessary for successfully Alloy 1 extrusion.
Table 3 lists the compositions of Alloys 1, 7, and 8-11. Alloys 1 and 7 were used for comparison with Alloys 8-11. Alloys 8-11 achieved similar extrudability to Reference Alloy 2 and reasonable cosmetics appeal. Alloys 8-11 also achieved a good combination of microstructure, color, strength, and ductility within different Si, Mg, Mn compositions from Alloys 2-7.
As shown in Table 3, Alloys 1, 7, 8, and 10 had the same Si content, i.e. 0.72 to 0.78 wt %. Alloys 8 and 10 had 0.090 to 0.110 wt % Mn, which was higher than Alloys 1 and 7. The difference between Alloys 8 and 10 was in Mg. Alloy 8 had 0.72 to 0.78 wt % Mg, which was slightly lower than 0.82-0.88 wt % Mg for Alloy 10, while other elements remained unchanged.
There was one element Mn slightly different between Alloy 7 and Alloy 8. Alloy 8 had slightly higher Mn than Alloy 7, i.e. 0.090 to 0.110 wt % Mn for Alloy 8 vs 0.0005 to 0.090 wt % Mn for Alloy 7.
There was one element Mn slightly different between Alloy 1 and Alloy 10. Alloy 10 had slightly higher Mn than Alloy 1, i.e. 0.090 to 0.110 wt % Mn for Alloy 10 vs 0.0005 to 0.090 wt % Mn for Alloy 1.
Alloys 9 and 11 had lower Si contents than Alloys 1, 7, 8, and 10. The difference between Alloys 9 and 11 were in Mg and Si. Alloy 9 had slightly lower Mg than Alloy 11, but slightly higher Si than Alloy 11. For example, Alloy 9 had 0.57 to 0.63 wt % Si and 0.77 to 0.83 wt % Mg, while Alloy 11 had 0.52 to 0.58 wt % Si and 0.87 to 0.93 wt % Mg.
An average yield strength of Alloy 1 was about 310 MPa, which was about 10 MPa higher than an average yield strength of 300 MPa of Alloy 7. Alloy 1 included additional 0.1 wt % Mg, which may provide slightly higher yield strength than Alloy 7.
Average yield strengths of Alloys 8 and 10 were about 330 MPa, which was about 30 MPa higher than the average yield strength of 300 MPa of Alloy 7. Alloys 8 and 10 included about 0.090 to 0.110 wt % Mn. The additional Mn helps form smaller AlFe(Mn)Si particles that may result in grain refinement and higher yield strength than Alloy 7. Note that AlFe(Mn)Si particles may be located at grain boundaries during casting. Then, recrystallization can occur to form new grains during extrusion such that these AlFe(Mn)Si particles may not be located at the grain boundaries in an extruded profile.
Alloy 9 had yield strengths ranging from about 270 to about 285 MPa. Alloy 11 had yield strengths ranging from about 250 to about 270 MPa. Alloy 9 included 0.57 to 0.63 wt % Si, which was lower than 0.72 to 0.78 wt % Si for Alloy 7. Alloy 11 included 0.52 to 0.58 wt % Si, which even lower than Alloy 9. The lower Si contents in Alloys 9 and 11 resulted in lower yield strength than that of Alloy 7.
Alloy 9 had tensile strengths ranging from about 290 to about 300 MPa. Alloy 11 had tensile strengths ranging from about 270 to about 290 MPa. The lower Si contents in Alloys 9 and 11 resulted in lower tensile strengths than that of Alloy 7.
Generally, for the 6000 series alloys including Reference Alloy 2, Alloys 1, 7, 8, and 10, lower elongation would be expected with increased yield strength. For example, Reference Alloy 2 had an average yield strength of about 230 MPa, which was about 30% lower than an average yield strength of about 300 MPa for Alloy 7, while the average elongation of Reference Alloy 2 was about 13.5%, which was higher than the average elongation of about 11% for Alloy 7. Alloys 8 and 10 included about 0.090 to 0.110 wt % Mn, which may form higher amount of constituent AlFeMnSi particles that may result in grain refinement and higher elongation than Alloy 7.
Alloy 9 had elongations ranging from 9% to 12%, about the same as Alloys 1 and 7. Alloy 11 had elongations ranging from 13% to 15.5%, which were higher than that of Alloys 1 and 7, but were similar to Alloys 8 and 10. The Mg contents of Alloys 9 and 11 were different from Alloy 10. The Mg contents of Alloys 9 and 11 were both higher than Alloy 8. Also, the Si contents of Alloys 9 and 11 were lower than Alloys 8 and 10. It seemed that Mg did not affect elongations of the alloys, while lower Si may increase elongation of Alloys 9 and 11 to be comparable to that of Alloys 8 and 10, which had higher elongations due to addition of about 0.090 to 0.110 wt % Mn.
Alloy 7 had the desirable anodization color b* and was used as a reference for comparing anodization color b* changes due to changes in elemental composition.
Also, Alloy 8 had Δb*of about 0.2, or b* 0.2 higher than Alloy 7, while Alloy 10 had Δb*of about 0.25, or b* 0.25 higher than Alloy 7. Alloys 8 and 10 included more Mn than Alloy 7, which seemed to increase b*.
Also, Alloy 9 had Δb*of about −0.1, or b* 0.1 lower than Alloy 7, while Alloy 11 had Δb*of about −0.4, or b* 0.4 lower than Alloy 7. Alloys 9 and 11 included less Si than Alloy 7, which seemed to reduce b*.
Further, Reference Alloy 2 had Δb*of about −0.4, or b* lower than Alloy 7.
Many 6000-series aluminum alloys rely on billet homogenization to convert an undesirable β-AlFeSi constituent particles (which are large and plate like), into α-AlFeSi particles, which are smaller than the β-AlFeSi constituent particles. Experiments showed that compositions had a strong influence on conversion of 3-AlFeSi to α-AlFeSi or β to a conversion during homogenization. More β to a conversion would result in better cosmetic appeal of the alloy.
Alloys were homogenized for the β to a conversion. In some variations, homogenization was performed at an elevated temperature (e.g. about 580° C.) for a period of time (e.g. 12 hours).
The homogenized alloys were also hot extruded to form extruded parts. In some variations, the extrusion was performed at an elevated temperature. The extruder typically heats up the alloy billet to about 500° C. before extrusion. Then, the extrusion deformation would further heat up the alloy, and then the extrusion comes out of the die at about 545° C. The extruded parts were analyzed for microstructure. For example, the extruded parts were cross-sectioned and polished. Then, scanning electron microscopy (SEM) images were taken for the polished cross-sectioned parts to reveal microstructure and to analyze elemental compositions by using energy dispersive spectroscopy (EDS). The particle sizes were then determined.
Alloys 8-11 were extruded by using the extrusion process similar to Alloy 1, but different from Alloys 2-7. Alloy 1.8-11 were extruded with the same setup as Alloys 2-7, including same billet diameters, extrusion press, and set of extrusion dies. However, some extrusion parameters were adjusted (e.g. temperature, and speed) in order to extrusion higher Mg alloys (e.g. Alloys 1 and 7).
Table 4 lists the average diameters of AlFeSi particles for Alloys 1 and 7-11 in extrusion. As shown in Table 4, Alloy 1 had 6.4 μm, Alloy 7 had 5.4 to 6.3 μm. Also, Alloy 8 had 3.9 μm and Alloy 10 had 3.6 μm. Alloys 8 and 10 with small addition of Mn had smaller average diameters than Alloys 1 and 7. Further, Alloy 9 had 5.3 μm and Alloy 11 had 5.3 μm. Alloys 9 and 11 with reduced Si content had smaller average diameters than Alloys 1 and 7.
Alloys 1 and 7 had larger average AlFeSi diameters than Alloys 8-11, which suggested low β-AlFeSi to α-AlFe(Mn)Si conversion, resulting in undesirable large β-AlFeSi particles in final extrusion. Alloys 1 and 7 included higher Si than Reference Alloy 2 and comparable Mn to Reference Alloy 2,
The microstructure was further analyzed and the phases of the AlFeSi particles were determined to be β-AlFeSi or α-AlFeSi. Surprisingly, a high conversion of β-AlFeSi to α-AlFeSi was observed for Alloy 10 with a small addition of Mn (0.090 to 0.110 wt % Mn). Without the small addition of Mn (e.g. 0.015 to 0.025 wt % Mn), a low conversion of β-AlFeSi to α-AlFeSi was observed for Alloy 7.
In some variations, the low β to a conversion is less than 20%. In some variations, the low β to a conversion is less than 15%. In some variations, the low β to α conversion is less than 10%. In some variations, the low β to a conversion is less than 5%.
In some variations, the high β to a conversion is at least 70%. In some variations, the high β to α conversion is at least 75%. In some variations, the high β to a conversion is at least 80%. In some variations, the high β to a conversion is at least 85%. In some variations, the high β to a conversion is at least 90%. In some variations, the high β to a conversion is at least 95%.
With higher Mn than Reference Alloy 2, Alloys 8 and 10 achieved high β to a conversion after homogenization, resulting in much smaller α-AlFeSi particles. The β to a conversion was associated with higher Mn, as evidenced by the smaller average AlFeSi diameters.
Also, with slightly higher Si than Reference Alloy 2, but lower Si than Alloys 8 and 10, Alloys 9 and 11 achieved most β to a conversion after homogenization, resulting in much smaller α-AlFeSi particles. The β to a conversion was associated with lower Si, as evidenced by the smaller average AlFeSi diameters.
As shown above, the elemental effects on properties have been evaluated for Alloys 8-11. Alloy compositions included 0.55 to 0.75 wt % Si, 0.75 to 0.90 wt % Mg, 0.02 to 0.11 wt % Mn. Table 5 summarizes the effects of the elemental composition of Si, Mg, and Mg on properties and processability of the alloys. As shown in Table 5, when Si increases, the yield strength and tensile strengths would increase, while elongation would decrease with Si content. When Si content becomes lower, constituent AlFeSi particle size can be reduced, and lower anodization color b* would be obtained.
Turning to Mn, when Mn increases, the yield strength and tensile strength as well as elongation increase, and smaller constituent AlFe(Mn)Si particle size were obtained. Lower anodization color b* would be obtained when Mn decreases.
Mg was found to provide concurrent strengthening and b* reduction. Mg can increase the extrusion flow stress, for example, an estimated 10% increase with every 0.1 wt % addition of Mg. As shown in Table 5, the yield strength and tensile strength of the alloy increase with Mg. Lower anodization color b* would be obtained for the alloy can be obtained with higher Mg.
It will be appreciated by those skilled in the art that other processing including sheet forming process can also be used for the disclosed alloys.
For some applications, the alloys may be tuned with a particular combination of properties, such as high strengths and ductility, and easy extrusion.
For some applications, the alloys may be tuned in compositions to have with a particular combination of properties, such as a desirable color, microstructure, cosmetic appeals after anodization, good strengths, good ductility, and good extrusion.
Table 6 lists the compositions of Alloys 12-15.
As shown in Table 6, Alloys 11-15 had the same Si content, i.e. 0.75 wt %. Alloys 12 and 13 had 0.035-0.045 wt % Mn, and Alloys 14 and 15 had 0.035-0.045 wt % Mn.
The disclosed aluminum alloys and methods can be used in the fabrication of electronic devices. An electronic device herein can refer to any electronic device known in the art. For example, such devices can include wearable devices such as a watch (e.g., an AppleWatch®). Devices can also be a telephone such a mobile phone (e.g., an iPhone®) a land-line phone, or any communication device (e.g., an electronic email sending/receiving device). The alloys can be a part of a display, such as a digital display, a TV monitor, an electronic-book reader, a portable web-browser (e.g., iPad®), and a computer monitor. The alloys can also be an entertainment device, including a portable DVD player, conventional DVD player, Blue-Ray disk player, video game console, music player, such as a portable music player (e.g., iPod®), etc. The alloys can also be a part of a device that provides control, such as controlling the streaming of images, videos, sounds (e.g., Apple TV®), or can be a remote control for an electronic device. The alloys can be a part of a computer or its accessories, such as the hard drive tower housing or casing for iPad, MacBook, or Mac Mini.
Any ranges cited herein are inclusive. The terms “substantially” and “about” used throughout this Specification are used to describe and account for small fluctuations. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%.
Having described several embodiments, it will be recognized by those skilled in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the invention. Accordingly, the above description should not be taken as limiting the scope of the invention.
Those skilled in the art will appreciate that the disclosed embodiments teach by way of example and not by limitation. Therefore, the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the method and system, which, as a matter of language, might be said to fall therebetween.
This patent application claims the benefit of U.S. Provisional Patent Application No. 63/038,261, entitled “High Strength Recycled Aluminum Alloys from Manufactured Scrap with Cosmetic Appeal,” filed on Jun. 12, 2020, and U.S. Provisional Patent Application No. 63/123,856 entitled “Aluminum Alloys with High Strength and Cosmetic Appeal,” filed Dec. 10, 2020, both of which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63123856 | Dec 2020 | US | |
| 63038261 | Jun 2020 | US |
