A 7XXX ALLOY FOR DEFENCE APPLICATIONS WITH A BALANCED ARMOR PIERCING FRAGMENTATION PERFORMANCE

Abstract

An armor component produced from a 7xxx series aluminum alloy, wherein the aluminum alloy consists essentially of: 8.4 wt. %≦Zn≦10.5 wt. %; 1.3 wt. %≦Mg≦2 wt. %; 1.2 wt. %≦Cu≦2 wt. %; at least one dispersoid forming element with a total dispersoid forming element content higher than 0.05 wt. %; the remainder substantially aluminum, incidental elements and impurities.

Claims

1. An armor component produced from a 7xxx series aluminum alloy, wherein the aluminum alloy consists essentially of: 8.4 wt. %≦Zn≦10.5 wt. % 1.3 wt. %≦Mg≦2 wt. %, 1.2 wt. %≦Cu≦2 wt. % at least one dispersoid forming element with a total dispersoid forming element content higher than 0.05 wt. %; the remainder substantially aluminum, incidental elements and impurities; wherein the 7XXX alloy is in the form of a plate having a thickness of about 0.5 to about 3 inches; wherein the 7XXX alloy is aged to achieve: (i) a fragment simulated particles V50 ballistic limit such that
V50(FSP 20 mm)>1633T.sup.2−1479T+1290 where T is the thickness plate (unit: inch) and the unit of V50 is feet/s. (ii) an armor piercing V50 ballistic limit such that:
V50(0.30 cal AP M2)>−282T.sup.2+1850T+610 where T is the thickness plate (unit: inch) and the unit of V50 is feet/s.

2. An armor component according to claim 1, wherein Mg/Zn≦0.20

3. An armor component according to claim 1, wherein 0.9≦Cu/Mg≦1.1

4. An armor component according to claim 1, wherein the dispersoid forming element is essentially zirconium, whose content is from 0.05 wt. % and 0.15 wt. %.

5. An armor component according to claim 1, wherein Fe<0.1 wt. % and Si<0.1 wt. %.

6. An armor component according to claim 1, wherein said 7xxx alloy in the form of a plate is manufactured by: a) casting said alloy into ingot form; b) homogenising said ingot; c) hot working said ingot to obtain a plate; d) solution heat treating; e) quenching; f) optionally stretching to obtain a plastic deformation from about 1 and about 3%; g) aging corresponding to the following treatment: about 4-8 hours at about 110° C.-130° C.+about 12-20 hours at about 140° C.-160° C.

7. An armor component according to claim 1, wherein said 7xxx alloy in the form of a plate is manufactured by: a) casting said alloy into ingot form; b) homogenising said ingot; c) hot working said ingot to obtain a plate; d) solution heat treating; e) quenching; f) optionally stretching to obtain a plastic deformation between about 1 and about 3%; g) aging, the total equivalent time at 150° C. of aging treatment not exceeding 25 h.

8. An armor component according to claim 1, wherein the 7xxx series aluminum alloy consists essentially of: 8.5 wt. %≦Zn≦9.5 wt. %; 1.5 wt. %≦Mg≦2 wt. %, 1.4 wt. %≦Cu≦1.8 wt. %; Fe<0.1 wt. %; Si<0.1 wt. %; 0.05 wt. %≦Zr≦0.15 wt. %; balance aluminum and incidental elements and impurities.

9. An armor component according to claim 8, wherein 1.8 wt. %≦Mg≦2 wt. %.

10. An armor component according to claim 1 to 9, wherein FSP V50 ballistics limit is such that:
V50(FSP 20 mm)>1633T.sup.2−1479T+1320   (I-a) where T is the thickness plate (unit: inch) and the unit of V50 is feet/s.

11. An armor component according to claim 1, wherein FSP V50 ballistics limit is such that:
V50(FSP 20 mm)>1633T.sup.2−1479T+1350   (I-b) where T is the thickness plate (unit: inch) and the unit of V50 is feet/s.

12. An armor component according to any of claim 1, wherein AP V50 ballistics limit is such that:
V50(0.30 cal AP M2)>−282T2+1850T+700   (II-a) where T is the thickness plate (unit: inch) and the unit of V50 is feet/s.

13. An armor component according to claim 1, wherein AP V50 ballistics limit is such that:
V50(0.30 cal AP M2)>−282T2+1850T+790   (II-b) where T is the thickness plate (unit: inch) and the unit of V50 is feet/s.

14. An armor component according to claim 1, wherein said plate is fusion welded and wherein the post-weld ultimate tensile strength is greater than 45%, optionally 50%, of the ultimate tensile strength before welding.

15. An armor component according to claim 1, wherein said plate is fusion welded and wherein the post-weld tensile strength is greater than 44 ksi, optionally 47 ksi.

16. A method of producing an armor component according to claim 1, comprising: a) casting said alloy into ingot form; b) homogenising said ingot; c) hot working said ingot to obtain a plate; d) solution heat treating; e) quenching; f) optionally stretching to obtain a plastic deformation from about 1 and about 3%; g) aging corresponding to the following treatment: about 4-8 hours at about 110° C.-130° C.+about 12-20 hours at about 140° C.-160° C.

17. A method of producing an armor component according to claim 1, comprising: a) casting said alloy into ingot form; b) homogenising said ingot; c) hot working said ingot to obtain a plate; d) solution heat treating; e) quenching; f) optionally stretching to obtain a plastic deformation between about 1 and about 3%; g) aging, the total equivalent time at 150° C. of aging treatment not exceeding 25 h.

Description

EXAMPLES

Example 1: AP and FSP Properties

[0038] Alloy plate products were made from alloys having the following chemical compositions, in weight percent:

TABLE-US-00001 TABLE 1 Cu/ Alloy Zn Mg Cu Fe Si Zr Ti Cr Mn Mg A 9.1 1.8 1.9 0.03 0.01 0.10 0.02 — 0.20* 1.1 B 10.1 1.9 1.6 0.06 0.03 0.12 0.04 — 0.20* 0.8 C 8.3 2.1 2.0 0.07 0.05 — 0.02 0.40* 0.40* 1.0 D 3.9 2.5 0.02 0.09 0.04 0.01 0.03 0.20* 0.25* 0.0 *nominal value

[0039] Alloys A and B have a chemistry according to the invention. Zinc content of alloy C is lower than the claimed minimum content. Ratio Mg/Zn of alloy C is approximately 0.25, i.e. higher than 0.20. Alloy D belongs to the AA7039-series aluminium alloys.

[0040] Plate products were made using the following process: [0041] casting an ingot of an alloy whose composition is indicated in table 1; [0042] homogenizing the ingot; [0043] hot working the homogenized ingot to arrive at an intermediate gauge; [0044] solution heat treating the plate; [0045] quenching; [0046] cold working said plate to arrive at a final gauge; [0047] artificial aging the stretched plate as indicated in table 2.

[0048] Plate products had different thicknesses varying from 0.9″ to 1.6″ and were tested for their ballistic properties. Two ballistic tests have been carried out pursuant to U.S. military standard MIL-STD-662F (1997), namely the armor piercing test using 0.3 inch (7.62 mm) projectiles and the FSP test using 20 mm fragment simulating projectiles. The results, listed in Table 2, are illustrated in FIGS. 1.a and 1.b.

[0049] AA7039-series plate products, in particular the thinnest plates (D-3, D-4 and D-5), have quite good FSP ballistic properties while they have poor AP ballistics properties. Thicker plates D-1 and D-2 have both poor AP and FSP ballistics properties.

[0050] Results on C alloy plate products show that when FSP performance is high, AP performance is poor (C-1) and when AP performance is high, FSP performance is poor (C-2 and C-3).

[0051] Plate products A-1, A-2, A-3, B-1 and B-2 have combined high AP and FSP performances. Sample A-4 has the same thickness as A-1. It was more largely over-aged than A-1. AP ballistic performance of A-4 is a bit lower than A-1. FSP ballistic performance A-4 is more significantly lower than A-1.

TABLE-US-00002 TABLE 2 Thickness Equivalent V50 (FSP V50 (0.3 cal Samples (inches) Temper time at 150° C.* 20 mm) ft/s AP M2) ft/s A-1 1.37 24 h@250° F. + 16 h@300° F. 16.9 2439 2839 (24 h@121° C. + 16 h@149° C.) A-2 1.57 24 h@250° F. + 16 h@300° F. 16.9 3042 3026 (24 h@121° C. + 16 h@149° C.) A-3 0.97 24 h@250° F. + 16 h@300° F. 16.9 1471 2325 (24 h@121° C. + 16 h@149° C.) A-4 1.37 24 h@250° F. + 35 h@300° F. 34.3 2244 2785 (24 h@121° C. + 35 h@149° C.) B-1 1.16 7 h@250° F. + 6 h@300° F. 6.6 1890 2588 (7 h@121° C. + 6 h@149° C.) B-2 1.52  7 h@250° F. + 12 h@350° F. 118.8 2972 2781  (7 h@121° C. + 12 h@177° C.) C-1 1.54 7 h@250° F. + 6 h@300° F. 6.6 3128 2687 (7 h@121° C. + 6 h@149° C.) C-2 1.18   T7651 1752 2641 C-3 1.57   T7651 2763 3097 D-1 1.49 T6 2747 2671 D-2 1.49 T6 2751 2691 D-3 1.25 T6 2057 2464 D-4 1.26 T6 1977 2419 D-5 1.29 T6 2082 2474 *heating rate 15° C./h

Example 2: Post Weld Strength

[0052] Couples of 0.5 inch thick plate products made of alloy A were butt welded along L direction. Other couples of 0.5 inch thick plate products made of alloy A were butt welded along LT direction. They were welded according to Ground Combat Vehicle Welding Code 19207, using MIG technology, a pulsed welding current and 1.2 mm or 1.6 mm diameter filler wires in AA5356 or in AA4043. Tensile test specimens were machined to measure the post-weld strength of these butt welds. Results of the tensile tests are shown in Table 3: in any case, the post-weld ultimate tensile strength is at least equal to 40.8 ksi (281 MPa), i.e. higher than 45% of the ultimate tensile strength before welding (607 MPA-88 ksi).

[0053] It can be noted that thanks to an appropriate choice of the filler wire, the butt weld has an ultimate tensile strength at least equal to 50% of the tensile strength before welding. It can be also noted that the butt weld has a tensile strength which is higher than 44 ksi (304 MPa), even higher than 47 ksi (324 MPa).

TABLE-US-00003 TABLE 3 UTS TYS MPa MPa Base metal 607 590 Filler wire: 4043 Ø 1.2 283 222 Filler wire: 4043 Ø 1.6 281 229 Filler wire: 5356 Ø 1.2 291 232 Filler wire: 5356 Ø 1.6 326 246