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NEW 6XXX ALUMINUM ALLOYS AND METHODS FOR PRODUCING THE SAME

20230175103 · 2023-06-08

    Inventors

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    International classification

    Abstract

    New 6xxx aluminum alloys are disclosed. In one approach, a new 6xxx aluminum alloy may include from 0.25-0.60 wt. % Fe, 0.8-1.2 wt. % Si, 0.35-1.1 wt. % Mg, 0.05-0.8 wt. % Mn, up to 0.30 wt. % Cu, up to 0.35 wt. % Zn, up to 0.15 wt. % Ti, up to 0.15 wt. % each of Cr, Zr, and V, the balance being aluminum, incidental elements and impurities. The new 6xxx aluminum alloys may be made from recycled aluminum alloys.

    Claims

    1. A 6xxx aluminum alloy sheet product comprising: 0.25-0.60 wt. % Fe; 0.05-0.8 wt. % Mn; wherein the (wt. % Fe) plus the (wt. % Mn) is at least ≥0.40 wt. %; 0.8-1.2 wt. % Si; 0.35-1.1 wt. % Mg; up to 0.30 wt. % Cu; up to 0.50 wt. % Zn; up to 0.15 wt. % Ti; up to 0.15 wt. % each of Cr, Zr, and V; the balance being aluminum, optional incidental elements and impurities; wherein the 6xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm.

    2. The 6xxx aluminum alloy sheet product of claim 1, wherein the 6xxx aluminum alloy sheet product includes at least 0.33 wt. % Fe.

    3. The 6xxx aluminum alloy sheet product of claim 2, wherein the 6xxx aluminum alloy sheet product includes at least 0.15 wt. % Mn.

    4. The 6xxx aluminum alloy sheet product of claim 3, wherein the 6xxx aluminum alloy sheet product includes at least 0.05 wt. % Cu.

    5. The 6xxx aluminum alloy sheet product of claim 4, wherein the 6xxx aluminum alloy sheet product includes at least 0.05 wt. % of at least one of Cr, V and Z.

    6. The 6xxx aluminum alloy sheet product of claim 5, wherein the 6xxx aluminum alloy sheet product includes at least 0.02 wt. % Ti.

    7. The 6xxx aluminum alloy sheet product of claim 1, wherein the (wt. % Fe) plus the (wt. % Mn) is at least ≥0.45 wt. %.

    8. The 6xxx aluminum alloy sheet product of claim 1, wherein 6xxx aluminum alloy sheet product realizes a TYS (LT) of not greater than 135 MPa in the T4 or T43 temper at 7 days of natural aging.

    9. The 6xxx aluminum alloy sheet product of claim 1, wherein 6xxx aluminum alloy sheet product realizes a TYS (LT) of not greater than 155 MPa in the T4 or T43 temper at 180 days of natural aging.

    10. The 6xxx aluminum alloy sheet product of claim 1, wherein 6xxx aluminum alloy sheet product realizes a total elongation (LT) of at least 18% in the T4 or T43 temper.

    11. The 6xxx aluminum alloy sheet product of claim 1, wherein 6xxx aluminum alloy sheet product realizes a delta r (Δr) of not greater than 0.20 in the T4 or T43 temper at 30 days of natural aging.

    12. The 6xxx aluminum alloy sheet product of claim 1, wherein 6xxx aluminum alloy sheet product realizes a n (4-6%) value of at least 0.265 in the T4 or T43 temper in the LT direction at 180 days of natural aging when tested in accordance with ASTM E646.

    13. A method comprising: (a) casting an aluminum alloy as an ingot or strip, wherein the aluminum alloy comprises: 0.25-0.60 wt. % Fe; 0.05-0.8 wt. % Mn; wherein the (wt. % Fe) plus the (wt. % Mn) is at least ≥0.40 wt. %; 0.8-1.2 wt. % Si; 0.35-1.1 wt. % Mg; up to 0.30 wt. % Cu; up to 0.50 wt. % Zn; up to 0.15 wt. % Ti; up to 0.15 wt. % each of Cr, Zr, and V; the balance being aluminum, optional incidental elements and impurities; (b) optionally homogenizing the aluminum alloy; (c) hot rolling the aluminum alloy to an intermediate gauge product or final gauge product; (d) optionally cold rolling the intermediate gauge product into the final gauge product; wherein, due to steps (c)-(d), the final gauge product has a thickness of from 0.5 to 4.0 mm; (e) solution heat treating and then quenching the final gauge product; (f) optionally pre-aging the solution heat treated and quenched final gauge product; (g) naturally aging the final gauge product, thereby realizing a T4 or T43 temper.

    14. The method of claim 13, wherein the casting step (a) comprises utilizing recycled aluminum alloy materials to produce the ingot or the strip.

    15. The method of claim 14, wherein the casting step (a) comprises melting the recycled aluminum alloy materials in combination with non-recycled aluminum materials, wherein, after the casting, the ingot or strip realizes the aluminum alloy composition recited in claim 13.

    Description

    BRIEF DESCRIPTION OF THE DRAWINGS

    [0052] FIGS. 1-2 are graphs illustrating the tensile yield strength and total elongation properties of the Example 1 alloys in various conditions.

    [0053] FIG. 3 is a graph illustrating the tensile yield strength and VDA bend results for the Example 1 alloys in the T43 temper.

    DETAILED DESCRIPTION

    Example 1

    [0054] Nine pilot-scale ingots of the aluminum alloys shown in Table 1 were conventionally scalped/peeled and then homogenized.

    TABLE-US-00001 TABLE 1 Composition of Ex, 1 Alloys (in wt. %)* Alloy** Si Fe Cu Mn Mg Cr Zn Ti XA25 1.00 0.44 0.16 0.40 0.60 0.03 0.03 0.02 XA26 0.99 0.42 0.15 0.38 0.90 0.03 0.04 0.02 XA27 1.00 0.17 0.16 0.40 0.62 0.03 0.03 0.02 XA28 1.01 0.44 0.14 0.39 0.60 0.03 0.31 0.02 XA29 0.98 0.44 0.16 0.41 0.40 0.03 0.02 0.02 XA30 0.98 0.44 0.14 0.41 0.65 0.15 0.03 0.02 XA31 0.63 0.40 0.14 0.41 0.89 0.03 0.02 0.02 XA32 0.98 0.43 0.15 0.15 0.62 0.03 0.02 0.02 XA66 0.81 0.13 0.05 0.07 0.59 0.03 0.02 0.02 *The balance of the alloy was incidental elements and impurities, where the alloy contained not greater than 0.03 wt. % of any one impurity, and where the alloy contained not greater than 0.10 wt. %, in total, of all impurities. **Alloy XA66 is a baseline alloy showing the level of performance in a low-iron 6xxx aluminum alloy. Alloys XA25-28, XA30, and XA32 are invention alloys. Alloys XA29 and XA31 are non-invention alloys.
    The ingots were then hot rolled to 3.53 mm (0.135 inch) followed by cold rolling (without any intermediate anneal) by about 70% to a final gauge of 1.02 mm (0.040 inch). The final gauge materials were then solution heat treated, air quenched and then processed to a T43 temper. The mechanical properties of the alloys were evaluated after naturally aging at 7, 30, 90 and 180 days, the results of which are shown in Tables 2-3 and 5-6, below. The delta r properties (Δr) at 30 days of natural aging were also calculated, the results of which are shown in Table 4, below, wherein delta r is calculated from the L, LT and 45° “r at 10” values, as explained above. A low delta r value is preferred and means a material is more isotropic.

    [0055] Strength and elongation are measured in accordance with ASTM E8 and B557. An “n value (4-6%)” is determined as the slope of the plastic portion of the stress strain curve between 4 and 6% elongation; the calculation method is provided in ASTM E646.

    TABLE-US-00002 TABLE 2 Mechanical Properties at 7 days of Natural Aging TYS UTS UTS − TYS Total Elong. Alloy Direction (MPa) (MPa) (MPa) (%) XA25 45 122.7 258.6 135.8 24.3 XA26 45 120.0 254.4 134.4 24.5 XA27 45 117.2 252.0 134.8 23.8 XA28 45 119.3 254.8 135.5 25.0 XA29 45 96.5 222.7 126.2 21.3 XA30 45 115.8 250.6 134.8 23.3 XA31 45 98.9 227.2 128.2 21.8 XA32 45 115.8 249.6 133.8 24.2 XA66 45 122.7 258.6 135.9 24.3 XA25 L 128.2 266.1 137.9 25.0 XA26 L 122.0 259.9 137.9 24.1 XA27 L 122.4 260.6 138.2 24.2 XA28 L 125.8 264.8 138.9 24.2 XA29 L 98.6 228.2 129.6 21.5 XA30 L 121.0 260.3 139.3 21.9 XA31 L 101.7 233.7 132.0 23.3 XA32 L 120.0 255.1 135.1 25.1 XA66 L 128.3 254.4 126.1 25.0 XA25 LT 122.7 254.4 131.7 21.5 XA26 LT 112.4 241.3 128.9 22.7 XA27 LT 120.3 253.7 133.4 21.5 XA28 LT 125.1 260.6 135.5 23.2 XA29 LT 96.5 223.7 127.2 20.8 XA30 LT 121.7 257.5 135.8 21.0 XA31 LT 97.2 221.0 123.8 18.6 XA32 LT 116.9 247.5 130.7 21.9 XA66 LT 122.7 254.4 131.7 21.5

    TABLE-US-00003 TABLE 3 Mechanical Properties at 30 days of Natural Aging TYS UTS UTS − TYS Total Elong. Alloy Direction (MPa) (MPa) (MPa) (%) XA25 45 127.9 259.9 132.0 24.6 XA26 45 124.8 256.5 131.7 21.4 XA27 45 123.1 255.5 132.4 24.7 XA28 45 124.8 258.6 133.8 25.1 XA29 45 103.1 228.9 125.8 21.9 XA30 45 124.5 257.2 132.7 23.2 XA31 45 106.2 232.7 126.5 21.2 XA32 45 120.3 251.0 130.7 24.0 XA66 45 129.6 249.3 119.6 25.1 XA25 L 131.3 265.8 134.4 23.0 XA26 L 128.2 263.0 134.8 24.2 XA27 L 123.4 258.9 135.5 23.2 XA28 L 131.0 268.9 137.9 24.3 XA29 L 107.2 235.1 127.9 20.0 XA30 L 126.9 263.7 136.9 21.6 XA31 L 108.9 238.6 129.6 22.4 XA32 L 127.6 261.0 133.4 24.6 XA66 L 134.8 257.5 122.7 24.2 XA25 LT 131.7 260.6 128.9 21.0 XA26 LT 128.9 259.6 130.7 22.0 XA27 LT 121.0 250.3 129.3 20.2 XA28 LT 128.6 262.3 133.8 22.5 XA29 LT 103.1 228.9 125.8 22.3 XA30 LT 126.9 259.6 132.7 20.9 XA31 LT 104.5 228.6 124.1 19.8 XA32 LT 122.4 251.0 128.6 22.1 XA66 LT 127.6 243.4 115.8 24.1

    TABLE-US-00004 TABLE 4 Delta R Properties at 30 days of Natural Aging Alloy Delta r XA25 0.025 XA26 0.125 XA27 0.040 XA28 0.050 XA29 0.070 XA30 0.130 XA31 0.095 XA32 0.038 XA66 0.243

    TABLE-US-00005 TABLE 5 Mechanical Properties at 90 days of Natural Aging TYS UTS UTS − TYS Total Elong. Alloy Direction (MPa) (MPa) (MPa) (%) XA25 LT 143.4 272.7 129.3 20.0 XA26 LT 137.9 268.9 131.0 23.0 XA27 LT 128.6 258.6 130.0 19.8 XA28 LT 137.9 272.7 134.8 23.1 XA29 LT 110.0 236.8 126.9 21.7 XA30 LT 136.2 269.2 133.1 20.3 XA31 LT 110.7 235.8 125.1 18.2 XA32 LT 126.5 255.8 129.3 23.4 XA66 LT 137.2 253.4 116.2 24.7

    TABLE-US-00006 TABLE 6 Mechanical Properties at 180 days of Natural Aging TYS UTS UTS-TYS Total n Value Alloy Direction (MPa) (MPa) (MPa) Elong. (%) (4-6%) XA25 LT 145.1 273.7 128.6 19.4 0.271 XA26 LT 138.9 267.2 128.2 21.9 0.271 XA27 LT 137.9 269.2 131.3 21.2 0.277 XA28 LT 146.9 281.3 134.4 22.8 0.270 XA29 LT 116.2 243.7 127.6 20.9 0.299 XA30 LT 140.7 273.0 132.4 21.9 0.272 XA31 LT 119.3 244.8 125.5 19.7 0.292 XA32 LT 133.1 260.6 127.6 20.3 0.278 XA66 LT 144.1 259.2 115.1 23.4 0.259

    [0056] The paint bake response of the materials was also evaluated. Specifically, at various days of natural aging (as shown in the below tables), specimens of alloys were (i) soaked at 365° F. (185° C.) for 20 minutes (no prestretch) (i.e., “0% PS+365° F./20 min.”), or (ii) imparted 2% prestretch and then soaked at 365° F. for 20 minutes (i.e., “200 PS+365° F./20 min.”). The same mechanical properties were then measured, the results of which are shown below in Tables 7-11, below.

    TABLE-US-00007 TABLE 7 Mechanical Properties at 7 days of Natural Aging plus 0% PS + 365° F./20 min. TYS UTS UTS − TYS Total Elong. Alloy Direction (MPa) (MPa) (MPa) (%) XA25 LT 195.8 293.7 97.9 17.2 XA26 LT 191.3 289.2 97.9 17.8 XA27 LT 199.6 295.1 95.5 16.5 XA28 LT 211.0 309.2 98.2 16.9 XA29 LT 167.5 264.4 96.9 16.6 XA30 LT 198.9 297.9 98.9 17.3 XA31 LT 167.5 264.8 97.2 16.9 XA32 LT 199.6 294.4 94.8 17.4 XA66 LT 216.2 297.5 81.3 18.0

    TABLE-US-00008 TABLE 8 Mechanical Properties at 90 days of Natural Aging plus 0% PS + 365° F./20 min. TYS UTS UTS − TYS Total Elong. Alloy Direction (MPa) (MPa) (MPa) (%) XA25 LT 194.1 296.8 102.7 17.0 XA26 LT 183.4 292.0 108.6 19.8 XA27 LT 176.9 284.8 107.9 18.7 XA28 LT 193.7 302.3 108.6 20.8 XA29 LT 148.2 257.2 108.9 18.7 XA30 LT 182.7 294.1 111.4 19.4 XA31 LT 157.6 265.1 107.6 17.6 XA32 LT 182.4 286.1 103.8 17.4 XA66 LT 197.2 288.6 91.4 19.7

    TABLE-US-00009 TABLE 9 Mechanical Properties at 180 days of Natural Aging plus 0% PS + 365° F./20 min. TYS UTS UTS − TYS Total Elong. Alloy Direction (MPa) (MPa) (MPa) (%) XA25 LT 191.6 291.9 100.3 15.65 XA26 LT 192.4 297.5 105.1 18.9 XA27 LT 180.9 284.4 103.4 17.2 XA28 LT 199.6 305.4 105.8 17.6 XA29 LT 152.7 258.6 105.8 18.3 XA30 LT 190.3 294.8 104.5 18.0 XA31 LT 161.3 267.5 106.2 17.3 XA32 LT 182.7 285.8 103.1 19.3 XA66 LT 199.9 289.6 89.6 19.7

    TABLE-US-00010 TABLE 10 Mechanical Properties at 7 days of Natural Aging plus 2% PS + 365° F./20 min. TYS UTS UTS − TYS Total Elong. Alloy Direction (MPa) (MPa) (MPa) (%) XA25 LT 253.4 313.4 60.0 14.1 XA26 LT 238.2 301.3 63.1 15.1 XA27 LT 247.9 309.6 61.7 15.4 XA28 LT 264.1 325.4 61.4 15.6 XA29 LT 220.3 282.7 62.4 15.3 XA30 LT 248.2 313.0 64.8 16.3 XA31 LT 204.8 273.0 68.3 14.0 XA32 LT 252.0 311.6 59.6 13.9 XA66 LT 251.7 308.2 56.8 14.9

    TABLE-US-00011 TABLE 11 Mechanical Properties at 30 days of Natural Aging plus 2% PS + 365° F./20 min. TYS UTS UTS − TYS Total Elong. Alloy Direction (MPa) (MPa) (MPa) (%) XA25 LT 253.0 312.0 59.0 14.5 XA26 LT 241.3 305.8 64.5 14.7 XA27 LT 240.6 302.7 62.1 15.5 XA28 LT 258.2 321.3 63.1 17.2 XA29 LT 215.5 279.2 63.8 14.2 XA30 LT 239.3 305.1 65.9 15.2 XA31 LT 202.0 272.7 70.7 16.2 XA32 LT 242.0 304.4 62.4 15.8 XA66 LT 243.0 304.1 61.0 17.5

    [0057] As shown, invention alloys, XA25-XA28, XA30 and XA32 realize tensile properties very close to the control alloy, XA66, despite the fact that the invention alloys contain notably higher iron and/or manganese levels. For instance, as shown in FIGS. 1-2, in the T43 temper and after simulated paint baking with 2% prestretch, the invention alloys realize comparable strength and total elongation to the XA66 baseline alloy, with alloys XA25 and XA28 performing particularly well. Non-invention alloys XA29 and XA31 realize notably lower tensile yield strengths. As also shown, the invention alloy are highly isotropic, realizing low delta r values (e.g., less than 0.20 delta r). The invention alloys are also realize high n (4-6%) values at 180 days of natural aging, indicating the material can elongate further prior to necking, which improves formability.

    [0058] In addition to ASTM B557 mechanical properties, the VDA bend properties of the materials were also tested, the results of which are shown in Table 12, below. VDA bend tests are conducted in accordance with VDA 238-100. VDA bend tests are used to assess, inter alia, a material's (a) ability to be riveted without cracking and (b) behavior in crash situations. The tests were conducted relative to the transverse orientation (LT), and the reported values are based on the average of four specimens used for each alloy tested. All properties are relative to the LT (long transverse) direction at 30 days of natural aging.

    TABLE-US-00012 TABLE 12 VDA Bend properties of Ex. 1 Alloys (30 days of natural aging) Avg Bend Angle α TYS Alloy (measured) (MPa)* XA25 114.5 130.7 XA26 102.0 124.1 XA27 105.8 126.1 XA28 116.4 134.5 XA29 122.7 105.2 XA30 106.2 122.0 XA31 113.7 108.9 XA32 109.0 124.8 XA66 119.1 129.3 *The illustrated TYS values are from materials in the T43 temper and from different specimens than those tested above.

    [0059] As shown (and as illustrated in FIG. 3), the invention alloys realize tensile and bend properties very close to the control alloy, XA66, despite the fact that the invention alloys contain notably higher iron and/or manganese levels. Non-invention alloys XA29 and XA31 realize notably lower strengths. The performance of the invention alloys is surprising because high levels of iron and manganese are known to result in deleterious particles. It is postulated that, by utilizing proper amounts of silicon, magnesium and copper in the base composition, the new 6xxx aluminum alloys described herein may be tolerant of the high iron and/or manganese levels, making the compositions able to utilize high levels of recycled materials in production.

    [0060] While a number of embodiments of the present invention have been described, it is understood that these embodiments are illustrative only, and not restrictive, and that many modifications may become apparent to those of ordinary skill in the art. Further still, unless the context clearly requires otherwise, the various steps may be carried out in any desired order, and any applicable steps may be added and/or eliminated.