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2XXX ALUMINUM ALLOYS

20210262065 · 2021-08-26

    Inventors

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    International classification

    Abstract

    New 2xxx aluminum alloys are disclosed. The new 2xxx aluminum alloys generally include from 0.08 to 0.20 wt. % Ti. The new 2xxx aluminum alloys may realize an improved combination of two or more of strength, fracture toughness, elongation, and corrosion resistance, for instance.

    Claims

    1. A 2xxx aluminum alloy comprising: from 0.08 to 0.20 wt. % Ti from 4.5 to 5.5 wt. % Cu; from 0.20 to 0.6 wt. % Mn; from 0.20 to 0.8 wt. % Mg; from 0.05 to 0.60 wt. % Ag; up to 1.0 wt. % Zn; up to 0.30 wt. % Fe; up to 0.20 wt. % Si; up to 0.25 wt. % Zr; up to 0.25 wt. % Cr; and up to 0.25 wt. % V; the balance being aluminum, incidental elements and impurities.

    2. The 2xxx aluminum alloy of claim 1, wherein the 2xxx aluminum alloy includes: from 0.08 to 0.13 wt. % Ti; from 4.8 to 5.0 wt. % Cu; from 0.40 to 0.60 wt. % Zn; from 0.30 to 0.40 wt. % Mn; from 0.30 to 0.50 wt. % Mg; from 0.30 to 0.40 wt. % Ag; from 0.08 to 0.12 wt. % Zr; up to 0.15 wt. % Fe; up to 0.10 wt. % Si; up to 0.05 wt. % Cr; and up to 0.05 wt. % V; the balance being aluminum, incidental elements and impurities, wherein the 2xxx aluminum alloy includes not greater than 0.15 wt. %, in total, of the impurities, and wherein the 2xxx aluminum alloy includes not greater than 0.05 wt. % of each of the impurities.

    3. The 2xxx aluminum alloy of claim 1, wherein the 2xxx aluminum alloy is in the form of a wrought product, and wherein there wrought product has a cross-sectional thickness of from at 12.7 mm to 305 mm.

    4. The 2xxx aluminum alloy of claim 3, wherein the wrought product is in the T8 temper and wherein the wrought product realizes a tensile yield strength (LT) of at least 390 MPa.

    5. The 2xxx aluminum alloy of claim 4, wherein the wrought product realizes a plane-strain (K.sub.IC) fracture toughness (T-L) of at least 30 MPa-sqrt-m.

    6. The 2xxx aluminum alloy of claim 5, wherein the wrought product realizes an elongation (LT) of at least 6.0%.

    7. The 2xxx aluminum alloy of claim 6, wherein the wrought product is (a) LT stress corrosion cracking resistant, (b) ST stress corrosion cracking resistant or (c) both LT stress corrosion cracking resistant and ST stress corrosion cracking resistant.

    8. A 2x39 aluminum alloy, wherein the 2x39 aluminum alloy comprises from 0.08 to 0.20 wt. % Ti.

    9. The 2x39 aluminum alloy of claim 8, wherein the 2x39 aluminum alloy includes from 0.05 to 0.20 wt. % Zr.

    10. The 2x39 aluminum alloy of claim 9, wherein the 2x39 aluminum alloy includes from 0.20 to 0.90 wt. % Zn.

    11. The 2x39 aluminum alloy of claim 8, wherein the 2x39 aluminum alloy is a 2039 aluminum alloy.

    12. The 2039 aluminum alloy of claim 11, wherein the 2039 aluminum alloy includes from 0.08 to 0.20 wt. % Ti and from 0 to 0.10 wt. % Zr.

    13. The 2x39 aluminum alloy of claim 8, wherein the 2x39 aluminum alloy is a 2139 aluminum alloy.

    Description

    BRIEF DESCRIPTION OF THE DRAWINGS

    [0064] FIGS. 1-4 are graphs illustrating the performance of alloys per Examples 2-3.

    DETAILED DESCRIPTION

    EXAMPLE 1

    Plate Testing

    [0065] Various 2xxx aluminum alloys were cast as ingots and homogenized. The composition of each ingot is shown in Table 1, below.

    TABLE-US-00002 TABLE 1 COMPOSITION OF ALLOYS (wt. %) Alloy Ti Cu Mg Mn Zr Zn Ag 1 0.01 4.95 0.50 0.34 0.11 0.02 0.34 2 0.05 4.97 0.48 0.34 0.11 0.02 0.34 3 0.06 4.96 0.50 0.35 0.07 0.02 0.34 4 0.10 4.83 0.49 0.35 0.07 0.02 0.33 5 0.05 4.95 0.29 0.34 0.07 0.02 0.34 6 0.10 4.84 0.30 0.34 0.06 0.02 0.34 7 0.10 4.82 0.37 0.35 0.07 0.49 0.34 8 0.10 4.97 0.40 0.34 0.07 0.02 0.49

    [0066] Each ingot contained not greater than 0.04 wt. % Si and not greater than 0.06 wt. % Fe. The balance of each alloy was aluminum, incidental elements and impurities, with no one impurity exceeding 0.05 wt. %, and with the total amount of impurities not exceeding 0.15 wt. %. After homogenization, the alloys were hot rolled to a final gauge of approximately 33 millimeters (mm), solution heat treated, and then quenched in about 195° F. (90.6° C.) water to simulate cooling at T/2 for a 4.5 inch (114.3 mm) thick plate. The alloys were then stretched about 2%, after which the alloys were artificially aged for about 32 hours at about 325° F. (162.8° C.). Approximate final gauges are provided in Table 3b, below.

    [0067] Various mechanical properties of the T8 aged aluminum alloy plates were measured in accordance with ASTM E8 and B557. Fracture toughness properties of some samples were also measured and in accordance with ASTM E399. The measured strength and fracture toughness properties are shown in Table 2, below.

    TABLE-US-00003 TABLE 2 Mechanical Properties (Long Transverse (LT) Direction) TYS (LT) TYS (LT) K.sub.IC (T-L) K.sub.IC (T-L) Elong. Alloy (MPa) (ksi) (MPa √m) (ksi √in.) (LT) (%) 1 427 61.9 31.1 28.3 11.1 2 427 61.9 34.9 31.8 10.4 3 407 59.0 31.4 28.6 8.6 4 419 60.8 31.9 29.0 9.0 5 382 55.4 38.8* 35.3* 12.9 6 388 56.3 42.2* 38.4* 11.4 7 428 62.1 36.3 33.0 10.0 8 415 60.2 34.3 31.2 10.0 *= K.sub.Q value

    [0068] The SCC (stress corrosion cracking) resistance of the alloys in the ST direction was also tested in accordance with ASTM G47, the results of which are shown in Table 3, below. As shown, the alloys with higher titanium realize improved SCC resistance.

    TABLE-US-00004 TABLE 3 SCC Resistance Properties (ST direction) Net Stress Samples Days to failure Ti in that Sample Sample Sample Alloy (wt. %) MPa (ksi) passed 1 2 3 1 0.01 241 (35.0) 0/3 7 7 7 1 0.01 276 (40.0) 0/3 2 7 3 2 0.05 241 (35.0) 1/3 7 9 P 2 0.05 276 (40.0) 0/3 3 8 7 3 0.06 241 (35.0) 0/3 10 7 11 3 0.06 276 (40.0) 1/3 9 10 P 4 0.10 241 (35.0) 2/3 23 P P 4 0.10 276 (40.0) 2/3 13 P P 5 0.05 241 (35.0) 1/3 7 7 P 5 0.05 276 (40.0) 0/3 7 7 7 6 0.10 241 (35.0) 2/3 23 P P 6 0.10 276 (40.0) 3/3 P P P 7 0.10 241 (35.0) 2/3 17 P P 7 0.10 276 (40.0) 3/3 P P P 8 0.11 241 (35.0) 2/3 14 P P 8 0.11 276 (40.0) 3/3 P P P * P = Passed 30 days

    [0069] As shown by the data, alloys having more titanium realized an improved combination of properties.

    EXAMPLE 2

    Thick Plate Testing

    [0070] One invention aluminum alloy and two conventional 2039 alloys were cast as ingots. The composition of each ingot is shown in Table 4, below.

    TABLE-US-00005 TABLE 4 Composition of Alloys (wt. %)* Alloy Ti Cu Mg Mn Zr Zn Ag 9 0.11 4.97 0.40 0.36 0.07 0.50 0.35 2039 (V1) 0.02 5.03 0.50 0.33 0.10 — 0.36 2039 (V2) 0.02 5.01 0.49 0.33 0.10 — 0.38 *Each ingot contained not greater than 0.04 wt. % Si and not greater than 0.06 wt. % Fe. The balance of each alloy was aluminum, incidental elements and impurities, with no one impurity exceeding 0.05 wt. %, and with the total amount of impurities not exceeding 0.15 wt. %.
    After homogenization, the alloys were hot rolled to a final gauge of approximately 127 millimeters (mm). After hot rolling, the alloys were cooled to room temperature, then solution heat treated, and then quenched in room temperature water (approx. 75° F. water). The alloys were then stretched either about 2% or 8%, after which the alloys were artificially aged at about 325° F. (162.8° C.) for various times. Thus, the alloys were in a T8 temper.

    [0071] Various mechanical properties of the T8 aluminum alloy plates were measured in accordance with ASTM E8 and B557. Fracture toughness properties of some samples were also measured and in accordance with ASTM E399. The measured strength and fracture toughness properties in the long-transverse direction are shown in Tables 5-8, below.

    TABLE-US-00006 TABLE 5 Properties of Alloy 9 aged at 325° F. with 2% Stretch LT (t/4) T-L (t/4) Aging Time TYS UTS Elong. K.sub.IC (Hrs) (ksi) (ksi) (%) (ksi-sqrt-in) 0 38.5 61 24.8 61.8* 8 56.5 67.7 12.8 53.1* 12 58.9 68.3 12.2 49.2 16 59.9 68.7 11.2 48.8 24 61.5 69.3 10.2 44.2 32 62.0 69.4 9.0 43.1 48 63.0 70.6 9.0 40.6 72 63.0 70.5 8.8 41 *= Kq value

    TABLE-US-00007 TABLE 6 Properties of Alloy 9 aged at 325° F. with 8% Stretch LT (t/4) T-L (t/4) Aging Time TYS UTS Elong. K.sub.IC (Hrs) (ksi) (ksi) (%) (ksi-sqrt-in) 0 46.3 62.9 20.2 62.6* 8 64.7 71.8 11.5 40.5 12 65.8 72.3 10 42 16 65.8 72.2 9.8 39.1 24 65.7 72.0 10.5 38 32 65.5 72.0 9.5 36.7 48 65.1 71.9 8.5 37.1 72 64.2 71.2 8.5 35.8 *= Kq value

    TABLE-US-00008 TABLE 7 Properties of the 2039 (V1) Alloy 9 aged at 325° F. with 2% Stretch LT (t/4) T-L (t/4) Aging Time TYS UTS Elong. K.sub.IC (Hrs) (ksi) (ksi) (%) (ksi-sqrt-in) 0 46.4 61.9 18.0 43.2 (K.sub.q value) 2 43.2 64.3 22.0 — 4 48.2 65.8 20.0 — 8 56.3 68 14.5 — 16 61.6 69.8 10.0 39 32 64.3 71.2 9.0 — 48 63.5 70.3 7.0 — 96 64.6 71.3 8.0 —

    TABLE-US-00009 TABLE 8 Alloy 2039 (V2) aged at 325° F. with 8% Stretch LT (t/4) T-L (t/4) Aging Time TYS UTS Elong. K.sub.IC (Hrs) (ksi) (ksi) (%) (ksi-sqrt-in) 0 46.6 62.1 17 48.6 (K.sub.q value) 2 54.1 67.5 17.5 — 4 60.7 69.4 14 — 8 65.6 71.9 10 — 16 67.3 72.9 9 32.5 32 67.3 72.7 7.5 — 48 66.5 72.1 7.5 — 96 64.9 71 7.5 —

    [0072] As shown in FIGS. 1-2, the invention alloy achieves an improved strength-fracture toughness trend over the conventional 2039 alloys.

    [0073] The SCC results of the alloys were also tested in accordance with ASTM G47, the results of which are provided in Tables 9-10, below. A 2xxx alloy passes the SCC test when no failures occur across all three samples over a period of at least 10 days (para 8.2).

    TABLE-US-00010 TABLE 9 SCC performance of Alloy 9 aged at 325° F.-ST (t/2)* Aging Net Days to failure Stretch time stress Specimen Specimen Specimen Alloy Lot (%) (h) (ksi) 1 2 3 9 ’533 2 0 36.3 12 5 3 8 36.3 3 12 3 12 36.3 3 3 5 16 36.3 10 5 3 24 36.3 10 10 12 32 36.3 10 20 12 48 36.3 43 T50 14 72 36.3 T50 T50 T50 9 ’531 8 0 36.3 2 14 12 8 36.3 10 12 12 12 36.3 52 54 80 16 36.3 T91 T91 91 24 36.3 31 91 T91 32 36.3 91 91 91 48 36.3 12 21 T50 72 36.3 T50 36 12 *T50 = still in test after 50 days; T91 = still in test after 91 days

    TABLE-US-00011 TABLE 10 SCC performance of Alloy 9 aged at 325° F.- ST (t/2) Aging Net Days to failure Stretch time stress Specimen Specimen Specimen Alloy (%) (h) (ksi) 1 2 3 2039 2 0 35 1 1 5 (V1) 2 35 3 3 4 4 35 1 1 3 8 35 1 3 4 16 35 3 4 5 32 35 3 4 5 48 35 3 3 6 96 35 7 7 7 2039 8 0 35 1 1 1 (V2) 2 35 1 1 5 4 35 3 4 4 8 35 5 7 10 16 35 3 4 8 32 35 3 4 4 48 35 4 3 4 96 35 3 6 7 96 35 3 6 7
    As shown, invention Alloy 9 passes the SCC test at multiple different aging times at both stretch levels. Conversely, none of the 2039 alloys are able to pass the SCC testing. Thus, not only does invention alloy 9 achieve an improved combination of strength and fracture toughness over the 2039 alloy, it also has much better corrosion resistance than the 2039 alloy.

    EXAMPLE 3

    Aging of Alloy 9 at 350° F.

    [0074] Samples of Alloy 9 from Example 2 were processed as per Example 2 with the exception that the alloys were aged at 350° F. instead of 325° F. Alloy properties were again measured, the results of which are shown in Tables 11-13, below.

    TABLE-US-00012 TABLE 11 Properties of Alloy 9 aged at 350° F. with 2% Stretch LT (t/4) T-L (t/4) Aging Time TYS UTS 5D Elong. K.sub.IC (Hrs) (ksi) (ksi) (%) (ksi-sqrt-in) 16 62 69.6 7.4 41.9 24 60.8 69.1 7.2 42.9 36 59.8 68.3 7.1 41.7

    TABLE-US-00013 TABLE 12 Properties of Alloy 9 aged at 350° F. with 8% Stretch LT (t/4) T-L (t/4) Aging Time TYS UTS 5D Elong. K.sub.IC (Hrs) (ksi) (ksi) (%) (ksi-sqrt-in) 16 63.5 70.7 7.6 36.8 24 62.3 69.8 7.0 37.4 36 60.9 69.2 6.6 38

    TABLE-US-00014 TABLE 13 SCC performance of Alloy 9 aged at 350° F.-ST (t/2)* Aging Net Days to failure Stretch time stress Specimen Specimen Specimen Alloy Lot (%) (h) (ksi) 1 2 3 9 ’533 2 16 36.3 T35 T35 T35 24 36.3 T35 T35 T35 36 36.3 T35 T35 T35 9 ’531 8 16 36.3 4 14 T35 24 36.3 T35 T35 T35 36 36.3 T35 T35 T35 *T35 = still in test after 35 days

    [0075] As shown in FIGS. 3-4, while the strength-toughness trends for the 350° F. aged alloys is slightly decreased relative to the 325° F. alloy, the SCC performance is improved, especially with the 2% stretched materials.

    [0076] While various embodiments of the present disclosure have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present disclosure.