Method of manufacturing thick aluminum alloy products

Abstract

The present application describes a novel method for producing a thick sheet heat-treatable aluminum alloy product. The new method may include hot rolling a heat treatable aluminum alloy ingot into a final gauge product, wherein the hot rolling includes hot rolling in at least two different hot rolling directions to achieve a final gauge sheet product having a thickness of 6.00 inches to 12.0 inches. The final gauge sheet product may then be processed to T-temper. As the material is hot-rolled in at least two different directions, the final gauge product can achieve an improved combination of properties, such as an improved combination of two or more of strength, ductility, fracture toughness, fatigue crack propagation resistance, isotropy, and the like.

Description

[0001] Cross-reference to related applications

[0002] This patent application claims priority to U.S. Provisional Patent Application No. 63 / 543,398, filed on October 10, 2023, entitled “METHOD OF MAKING THICK ALUMINUM ALLOY PRODUCTS”, which is incorporated herein by reference in its entirety. Background Technology

[0003] Aluminum alloys are useful in a wide range of applications. However, improving one property of an aluminum alloy without compromising another is elusive. For example, it is difficult to increase the strength of forged aluminum alloys without affecting other properties such as fracture toughness or corrosion resistance. Summary of the Invention

[0004] In a broader sense, this patent application relates to a novel method for producing heat-treatable sheet aluminum alloy products. The novel method may include hot rolling a heat-treatable aluminum alloy ingot into a final-size product, wherein the hot rolling comprises hot rolling in at least two different hot rolling directions to achieve a final-size sheet product with a thickness of 6.00 inches to 12.0 inches. The final-size sheet product can then be processed to T-temper. At least in part due to hot rolling the material in at least two different directions, the final-size product can achieve an improved combination of properties, such as an improved combination of two or more of the following: strength, ductility, fracture toughness, fatigue crack propagation resistance, and isotropy. Further details are provided below.

[0005] i. Production methods

[0006] a. Hot rolling

[0007] As described above, the novel method described herein relates to hot rolling a heat-treatable aluminum alloy ingot into a final-specification product, wherein the hot rolling step comprises hot rolling in at least two different hot rolling directions. In one embodiment, the hot rolling step comprises performing a first hot rolling of the heat-treatable aluminum alloy ingot in a first rolling direction and a second hot rolling of the heat-treatable aluminum alloy ingot in a second rolling direction, the second rolling direction being different from the first rolling direction. In one embodiment, the second rolling direction is transverse to the first rolling direction. In one embodiment, the second rolling direction is generally perpendicular to the second first rolling direction.

[0008] The first hot rolling step may include one or more hot rolling passes. In one embodiment, the first hot rolling step includes multiple hot rolling passes. In one embodiment, the first hot rolling step includes hot rolling the ingot into an intermediate specification product.

[0009] The second hot rolling step may include one or more hot rolling passes. In one embodiment, the second hot rolling step includes multiple hot rolling passes. In one embodiment, the second hot rolling step includes hot rolling an intermediate specification product into a final specification product.

[0010] Typically, all the hot rolling passes of the first hot rolling step are completed, followed by all the hot rolling passes of the second hot rolling step. However, in other embodiments, a subset of the hot rolling passes of the first hot rolling step may be completed, followed by all or a subset of the hot rolling passes of the second hot rolling step. Therefore, the hot rolling passes of the first and second hot rolling steps can be alternated as needed until the final product specification is achieved.

[0011] In one embodiment, the first rolling direction is associated with a transverse direction, and the second rolling direction is associated with a longitudinal direction. In another embodiment, the first rolling direction is associated with a longitudinal direction, and the second rolling direction is associated with a transverse direction.

[0012] Other rolling directions may be used. In one embodiment, a method includes performing a third hot rolling in a third rolling direction, which is different from the first or second rolling direction. In one embodiment, the third rolling direction is associated with a 45° direction. The third hot rolling step may include one or more hot rolling passes. The third hot rolling step may be performed before, after, or iteratively in combination with the first and / or second hot rolling steps.

[0013] As described above, hot rolling typically produces final-size sheet metal products. These final-size sheet metal products typically have a thickness of 6.00 inches to 12.0 inches and are suitable for aerospace structural applications, as described in further detail below. Final-size dimensions are determined according to ANSI H35.2 (2001). In one embodiment, the final-size product has a thickness of no more than 11.5 inches. In another embodiment, the final-size product has a thickness of no more than 11.0 inches. In yet another embodiment, the final-size product has a thickness of no more than 10.5 inches. In yet another embodiment, the final-size product has a thickness of no more than 10.0 inches.

[0014] In one method, the final specification product has a thickness of 6.01 inches to 6.50 inches, and the rolled (finished) width of the final specification sheet product is at least 60% larger than the width of the heat-treatable aluminum alloy ingot. The width of the heat-treatable aluminum alloy ingot is the width of the ingot before the hot rolling step begins. In one embodiment, the rolled width of the sheet is at least 65% larger than the width of the heat-treatable aluminum alloy ingot. In another embodiment, the rolled width of the sheet is at least 70% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 75% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 80% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 85% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 90% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 95% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 100% greater than the width of the heat-treatable aluminum alloy.

[0015] In another method, the final specification product has a thickness of 6.51 inches to 7.00 inches, and the rolled width of the final specification sheet product is at least 50% larger than the width of the heat-treatable aluminum alloy ingot. The width of the heat-treatable aluminum alloy ingot is the width of the ingot before the hot rolling step begins. In one embodiment, the rolled width of the sheet is at least 55% larger than the width of the heat-treatable aluminum alloy ingot. In another embodiment, the rolled width of the sheet is at least 60% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 65% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 70% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 75% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 80% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 85% greater than the width of the heat-treatable aluminum alloy. In another embodiment, the rolled width of the sheet metal is at least 90% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 95% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 100% greater than the width of the heat-treatable aluminum alloy.

[0016] In yet another method, the final specification product has a thickness of 7.01 inches to 7.50 inches, and the rolled width of the final specification sheet product is at least 40% larger than the width of the heat-treatable aluminum alloy ingot. The width of the heat-treatable aluminum alloy ingot is the width of the ingot before the hot rolling step begins. In one embodiment, the rolled width of the sheet is at least 45% larger than the width of the heat-treatable aluminum alloy ingot. In another embodiment, the rolled width of the sheet is at least 50% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 55% larger than the width of the heat-treatable aluminum alloy. In another embodiment, the rolled width of the sheet is at least 60% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 65% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 70% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 75% greater than the width of the heat-treatable aluminum alloy. In another embodiment, the rolled width of the sheet metal is at least 80% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 85% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 90% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 95% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 100% greater than the width of the heat-treatable aluminum alloy.

[0017] In another method, the final specification product has a thickness of 7.51 inches to 8.00 inches, and the rolled width of the final specification sheet product is at least 30% larger than the width of the heat-treatable aluminum alloy ingot. The width of the heat-treatable aluminum alloy ingot is the width of the ingot before the hot rolling step begins. In one embodiment, the rolled width of the sheet is at least 35% larger than the width of the heat-treatable aluminum alloy ingot. In another embodiment, the rolled width of the sheet is at least 40% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 45% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 50% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 55% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 60% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 65% greater than the width of the heat-treatable aluminum alloy. In another embodiment, the rolled width of the sheet metal is at least 70% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 75% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 80% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 85% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 90% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 95% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 100% greater than the width of the heat-treatable aluminum alloy.

[0018] In yet another method, the final specification product has a thickness of 8.01 inches to 12.00 inches, and the rolled width of the final specification sheet product is at least 25% larger than the width of the heat-treatable aluminum alloy ingot. The width of the heat-treatable aluminum alloy ingot is the width of the ingot before the hot rolling step begins. In one embodiment, the rolled width of the sheet is at least 30% larger than the width of the heat-treatable aluminum alloy ingot. In another embodiment, the rolled width of the sheet is at least 35% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 40% larger than the width of the heat-treatable aluminum alloy. In another embodiment, the rolled width of the sheet is at least 45% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 50% larger than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet is at least 55% larger than the width of the heat-treatable aluminum alloy. In another embodiment, the rolled width of the sheet metal is at least 60% greater than the width of the heat-treatable aluminum alloy. In another embodiment, the rolled width of the sheet metal is at least 70% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 75% greater than the width of the heat-treatable aluminum alloy. In another embodiment, the rolled width of the sheet metal is at least 80% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 85% greater than the width of the heat-treatable aluminum alloy. In another embodiment, the rolled width of the sheet metal is at least 90% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 95% greater than the width of the heat-treatable aluminum alloy. In yet another embodiment, the rolled width of the sheet metal is at least 100% greater than the width of the heat-treatable aluminum alloy.

[0019] b. Post-hot rolling processing

[0020] As described above, after hot rolling, the method may include processing the final-size aluminum alloy product to T-temper, as defined by ANSI H35.1 (2009). In one embodiment, after hot rolling, the final-size sheet product may be cooled to room temperature and stored. In one embodiment, after hot rolling (and cooling or not cooling to room temperature), the final-size sheet product is subjected to solution heat treatment and then quenched. In one embodiment, the method does not involve cold rolling of the sheet before solution heat treatment, i.e., no cold rolling is performed during or after hot rolling but before solution heat treatment. Quenching may be cold water quenching, such as by immersing the final-size product in a cold water bath or by spraying cold water, or using other suitable quenching media. After solution heat treatment and quenching, the final-size aluminum alloy product may be subjected to natural aging for 24-48 hours and subjected to nominal stretching (e.g., 1-5%) to achieve flatness, or stress relief may be performed by other means known to those skilled in the art. Following natural aging and stretching (if applicable), the final specification product may be artificially aged to a suitable temper (such as either T6 or T7 temper). In one embodiment, the tempering is a T7X temper, such as any one of T73, T74, T76, T77, or T79 temper. In one embodiment, the T7X temper is a T7X51 temper, as defined in ANSI H35.1 (2009).

[0021] ii. Microstructure

[0022] As described above, the novel method presented herein enables the final aluminum alloy sheet products to possess improved thickness properties, such as a combination of improvements in two or more of the following: strength, ductility, fracture toughness, fatigue crack propagation resistance, and isotropy. The microstructural characteristics of the novel heat-treatable thick aluminum alloy products can at least partially contribute to these improvements.

[0023] In one approach, the final specification product achieves an ARproj of no more than 2.75. Awt As determined according to the microstructure evaluation procedure described below. As explained in the microstructure evaluation procedure, ARproj Awt It is L proj :LT proj The ratio, and a quantitative method, is used to determine the average grain aspect ratio of the grains in the L-LT plane at the product T / 4 position of the final specification product. In one embodiment, the final specification product achieves an ARproj of not more than 2.5. Awt In another embodiment, the final specification product achieves an ARproj of no more than 2.4. AwtIn yet another embodiment, the final specification product achieves an ARproj of no more than 2.3. Awt In another embodiment, the final specification product achieves an ARproj of no more than 2.2. Awt In yet another embodiment, the final specification product achieves an ARproj of no more than 2.1. Awt In another embodiment, the final specification product achieves an ARproj of no more than 2.0. Awt In yet another embodiment, the final specification product achieves an ARproj of no more than 1.9. Awt In another embodiment, the final specification product achieves an ARproj of no more than 1.8. Awt In another embodiment, the final specification product achieves an ARproj of no more than 1.7. Awt In yet another embodiment, the final specification product achieves an ARproj of no more than 1.6. Awt In another embodiment, the final specification product achieves an ARproj of no more than 1.5. Awt In yet another embodiment, the final specification product achieves an ARproj of no more than 1.4. Awt In another embodiment, the final specification product achieves an ARproj of no more than 1.3. Awt In yet another embodiment, the final specification product achieves an ARproj of no more than 1.2. Awt .

[0024] iii. Characteristics

[0025] As described above, the novel method described herein can enable the final aluminum alloy sheet product to have improved thickness characteristics, such as a combination of improvements in two or more of the following: strength, ductility, fracture toughness, fatigue crack propagation resistance, and isotropy.

[0026] In one approach, the final product achieves improved strength isotropy. For example, the final product may achieve a longitudinal tensile yield strength (TYS-L) and a long transverse tensile yield strength (TYS-LT), where the absolute value of [(TYS-L) minus (TYS-LT)] divided by (TYS-L) is no greater than 5%. Since the longitudinal and long transverse yield strengths are generally similar, the product can be considered to be strength isotropic. In one embodiment, the absolute value of [(TYS-L) minus (TYS-LT)] divided by (TYS-L) is no greater than 4.5%. In another embodiment, the absolute value of [(TYS-L) minus (TYS-LT)] divided by (TYS-L) is no greater than 4.0%. In yet another embodiment, the absolute value of [(TYS-L) minus (TYS-LT)] divided by (TYS-L) is no greater than 3.5%. In another embodiment, the absolute value of [(TYS-L) minus (TYS-LT)] divided by (TYS-L) is not greater than 3.0%. In yet another embodiment, the absolute value of [(TYS-L) minus (TYS-LT)] divided by (TYS-L) is not greater than 2.5%. In yet another embodiment, the absolute value of [(TYS-L) minus (TYS-LT)] divided by (TYS-L) is not greater than 2.0%.

[0027] In one approach, the final specification product has improved elongation isotropy. For example, the final specification product can achieve both longitudinal elongation (Elong.-L) and long transverse elongation (Elong.-LT). In one embodiment, the final specification sheet product is isotropic in elongation, wherein the absolute value of [(Elong.-L) minus (Elong.-LT)] divided by (Elong.-L) is not greater than 25%. Since the longitudinal and long transverse elongations are generally similar, the product can be considered isotropic in elongation. In one embodiment, the absolute value of [(Elong.-L) minus (Elong.-LT)] divided by (Elong.-L) is not greater than 20%. In another embodiment, the absolute value of [(Elong.-L) minus (Elong.-LT)] divided by (Elong.-L) is not greater than 15%. In yet another embodiment, the absolute value of [(Elong.-L) minus (Elong.-LT)] divided by (Elong.-L) is not greater than 10%. In another embodiment, the absolute value of [(Elong.-L) minus (Elong.-LT)] divided by (Elong.-L) is not greater than 8%. In yet another embodiment, the absolute value of [(Elong.-L) minus (Elong.-LT)] divided by (Elong.-L) is not greater than 6%.

[0028] In one approach, the final specification product exhibits improved fracture toughness isotropic properties. For example, the final specification product can achieve LT K. IC Fracture toughness and TL K IC Fracture toughness. In one embodiment, the final specification sheet product is isotropic in fracture toughness, wherein [(LT K IC Subtract (TL K) IC Divide by (LT K) IC The absolute value of ) is not greater than 20%. Since the longitudinal and transverse fracture toughness values ​​are generally similar, the product can be considered to have isotropic fracture toughness. In one embodiment, the [(LT K] IC Subtract (TL K) IC Divide by (LT K) IC The absolute value of ) is no greater than 18%. In another embodiment, the [(LT K IC Subtract (TL K) IC Divide by (LT K) IC The absolute value of ) is no greater than 16%. In yet another embodiment, the [(LT K IC Subtract (TL K) IC Divide by (LT K) IC The absolute value of ) is no greater than 14%. In another embodiment, the [(LT K)] IC Subtract (TL K) IC Divide by (LT K) IC The absolute value of ) is not greater than 12%. In yet another embodiment, the [(LT K)] IC Subtract (TL K) IC Divide by (LT K) IC The absolute value of ) is not greater than 10%. In another embodiment, the [(LT K IC Subtract (TL K) IC Divide by (LT K) IC The absolute value of ) is not greater than 8%. In yet another embodiment, the [(LT K IC Subtract (TL K) IC Divide by (LT K) IC The absolute value of ) is no greater than 6%. In another embodiment, the [(LT K IC Subtract (TL K) IC Divide by (LT K) IC The absolute value of ) is no greater than 4%. In yet another embodiment, the [(LT K IC Subtract (TL K) IC Divide by (LT K)IC The absolute value of ) is no greater than 2%.

[0029] In another approach, improved damage tolerance is achieved. In one embodiment, when ΔK is 20, the final specification product achieves at least a 2% improvement in fatigue crack propagation resistance compared to the baseline product, wherein the baseline product has an equivalent composition, tempering, and specifications, and wherein the baseline product is produced by hot rolling only in the longitudinal direction. In another embodiment, when ΔK is 20, the final specification product achieves at least a 4% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, when ΔK is 20, the final specification product achieves at least a 6% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, when ΔK is 20, the final specification product achieves at least an 8% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, when ΔK is 20, the final specification product achieves at least a 10% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, when ΔK is 20, the final specification product achieves at least a 12% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 20, the final specification product achieves at least a 14% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 20, the final specification product achieves at least a 16% improvement in fatigue crack propagation resistance compared to the baseline product.

[0030] In one embodiment, when ΔK is 25, the final specification product achieves at least a 5% improvement in fatigue crack propagation resistance compared to the baseline product, wherein the baseline product has an equivalent composition, tempering, and specifications, and wherein the baseline product is produced by hot rolling only in the longitudinal direction. In another embodiment, when ΔK is 25, the final specification product achieves at least a 10% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, when ΔK is 25, the final specification product achieves at least a 15% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, when ΔK is 25, the final specification product achieves at least a 20% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, when ΔK is 25, the final specification product achieves at least a 22% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, when ΔK is 25, the final specification product achieves at least a 24% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 25, the final specification product achieves at least a 26% improvement in fatigue crack propagation resistance compared to the baseline product. In another embodiment, where ΔK is 25, the final specification product achieves at least a 28% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 25, the final specification product achieves at least a 30% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 25, the final specification product achieves at least a 32% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 25, the final specification product achieves at least a 34% improvement in fatigue crack propagation resistance compared to the baseline product.

[0031] In one embodiment, when ΔK is 30, the final specification product achieves at least a 5% improvement in fatigue crack propagation resistance compared to the baseline product, wherein the baseline product has an equivalent composition, tempering, and specifications, and wherein the baseline product is produced by hot rolling only in the longitudinal direction. In another embodiment, when ΔK is 30, the final specification product achieves at least a 10% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, when ΔK is 30, the final specification product achieves at least a 15% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, when ΔK is 30, the final specification product achieves at least a 20% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, when ΔK is 30, the final specification product achieves at least a 22% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, when ΔK is 30, the final specification product achieves at least a 24% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 30, the final specification product achieves at least a 26% improvement in fatigue crack propagation resistance compared to the baseline product. In another embodiment, where ΔK is 30, the final specification product achieves at least a 28% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 30, the final specification product achieves at least a 30% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 30, the final specification product achieves at least a 32% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 30, the final specification product achieves at least a 34% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 30, the final specification product achieves at least a 36% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 30, the final specification product achieves at least a 38% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 30, the final specification product achieves at least a 40% improvement in fatigue crack propagation resistance compared to the baseline product. In another embodiment, where ΔK is 30, the final specification product achieves at least a 42% improvement in fatigue crack propagation resistance compared to the baseline product. In yet another embodiment, where ΔK is 30, the final specification product achieves at least a 44% improvement in fatigue crack propagation resistance compared to the baseline product.

[0032] iv. Composition

[0033] As described above, the novel method is generally applicable to heat-treatable aluminum alloy products. Heat-treatable aluminum alloy products are those that can undergo artificial aging treatment to achieve precipitation hardening. Suitable heat-treatable aluminum alloy products include 2xxx, 6xxx, and 7xxx aluminum alloy products. In one embodiment, the heat-treatable aluminum alloy product is a 2xxx aluminum alloy product, with or without lithium. A 2xxx aluminum alloy product is considered to contain lithium when it contains more than 0.05 wt.% Li. In another embodiment, the heat-treatable aluminum alloy product is a 6xxx aluminum alloy product. In yet another embodiment, the heat-treatable aluminum alloy product is a 7xxx aluminum alloy product. Suitable 7xxx aluminum alloys for thick plates include, for example, the following known 7xxx aluminum alloys: 7050, 7150, 7050A, 7040, 7140, 7085, 7185, 7065, 7036, 7136, 7081, and 7181. The Aluminum Association defines the composition of these alloys in its document "International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys," January 2015. In one embodiment, 2xxx aluminum alloy products for thick plates are 2050 or 2195 aluminum alloy products.

[0034] v. Product application

[0035] The novel aluminum alloy described in this article can be used in a variety of product applications, such as aerospace applications. For example, the new alloy can be used as wing ribs, wing spars, frames (thickness), fuselage side parts / accessories, large parts / lugs, bulkheads, integral / combination cargo hold floor structures, and landing gear / racks / engine support structures for aircraft / aerospace vehicles. The new alloy can also be used in armored products, such as armored vehicles.

[0036] vi. Define

[0037] "Forged aluminum alloy products" refers to aluminum alloy products that have been hot-worked after casting, and includes rolled products (sheets or plates), forged products and extruded products.

[0038] "Hot working," such as hot rolling, refers to processing aluminum alloy products at high temperatures, typically at least 121.1°C (250°F). During hot working, strain hardening is limited / avoided, which is what distinguishes hot working from cold working.

[0039] "Cold working," such as cold rolling, refers to processing aluminum alloy products at temperatures not considered hot working temperatures, generally below about 121.1°C (250°F) (e.g., at ambient temperature).

[0040] The definition of tempering conforms to ANSI H35.1 (2009) published by the Aluminum Association, entitled "American National Standard Alloy and Temper Designation Systems for Aluminum".

[0041] Strength and elongation were measured according to ASTM E8 / E8M-21 and B557-15. Fracture toughness was measured according to ASTM E399-20a and B645-21.

[0042] vii. Microstructure evaluation procedure

[0043] The following procedures and definitions apply to measuring the microstructural features (e.g., grain long axis and short axis, projection distance, aspect ratio) of products manufactured according to this patent application.

[0044] EBSD (Electron Backscattering Diffraction) analysis will be performed using the following EBSD sample procedure. Prior to measurement, the EBSD sample is prepared using standard metallographic sample preparation methods. For example, the EBSD sample undergoes metallographic preparation and is then polished (e.g., using 0.05 μm colloidal silica). The sample is then etched by immersion in a 0.5% hydrofluoric acid (HF) solution for 5 seconds, followed by rinsing and drying.

[0045] The “EBSD Sample Procedure” is as follows:

[0046] ● The software used was APEX EBSD Collection Software (version 2) (EDAX Inc., New Jersey, USA) or equivalent, connected to a VelocitySuper EBSD camera (EDAX Inc., New Jersey, USA) or equivalent. The scanning electron microscope (SEM) was APREO SField Emission Gun (Thermo Fisher Scientific, Waltham, MA, USA) or equivalent.

[0047] ● The SEM operating parameters for EBSD scanning were: 20 kV accelerating voltage, 51 nA beam current, 18 mm working distance, 68° tilt level, and dynamic focusing. The collection mode was a composite scan, consisting of multiple images offset by a single image size along the x and y axes to ensure no overlap; a square grid was used to collect the points. Selection was made to collect orientation during the analysis (i.e., Hough peak information was not collected). The collected data was output as a *.osc file. This data can be used to calculate aspect ratio parameters, as described below.

[0048] EBSD scanning will be performed on the rolling plane (i.e., L-LT) to characterize the microstructure at one-quarter thickness (T / 4) of the final sheet product. The scanned area should be at least 20.0 mm in the horizontal direction and at least 15.0 mm in the vertical direction. Preferably, the scanned area should be at least 400 mm. 2 More than 25 million data points were generated using a 4.0 μm step size.

[0049] The term "grain" has the meaning defined in ASTM E267-13 (2019) §3.1.6, namely, "a set of adjacent points with similar orientations on a scanned grid. The set is surrounded by a perimeter, wherein an erroneous orientation across the perimeter exceeds a specified tolerance value." For each measured grain, the commercial software (OIM Analysis, version 8.5.1 or equivalent) reports several statistics in the 'grain file', including:

[0050] ● Edge Grains: A value of 1 is given if a grain has at least one point intersecting the perimeter of the composite scan. A value of 0 for "Inner Grains" indicates that all points are contained within the plot.

[0051] ● Grain area (square micrometers), A i ;

[0052] ● Grain ellipse fitting major axis length (micrometers), e maj ;

[0053] ● Grain ellipse fitting minor axis length (micrometers), e min ;as well as

[0054] ● The orientation (degrees) of the major axis relative to the horizontal direction, θ, ranges from 0 to 180°.

[0055] Calculate the projections of each grain onto the longitudinal (L) and longitudinal transverse (LT) directions, respectively. proj and LT projThe longitudinal (L) direction typically corresponds to the main rolling direction, and the long transverse (LT) direction typically corresponds to the direction transverse (e.g., perpendicular) to the main rolling direction.

[0056] Figure 1 L is shown in proj and LT proj Various non-limiting examples are shown, which are non-limiting example EBSD plots of the L-LT plane, where grain boundaries are superimposed on best-fit ellipses. As illustrated:

[0057] ● L proj Calculated by taking the maximum of any of the following:

[0058] abs [(e maj )*(cos θ)] or abs [(e min )*(sin θ)];and

[0059] ● LT proj Calculated by taking the maximum of any of the following:

[0060] abs [(e min )*(cos θ)] or abs [(e maj )*(sin θ)];

[0061] Where abs[ ] is the absolute value of the calculation to ensure that the projection is positive.

[0062] The ratio of these two projections (L) proj :LT proj ) is the aspect ratio parameter (AR) proj ),Right now:

[0063] ARproj = L proj / LT proj .

[0064] For all internal grains, the "area-weighted average aspect ratio" can also be calculated using the following equation:

[0065] .

[0066] The "area-weighted average aspect ratio" can indicate the degree of isotropy of the final product.

[0067] While several embodiments of this disclosure have been described, it should be understood that these embodiments are merely illustrative and not restrictive, and many modifications will be apparent to those skilled in the art. Furthermore, unless the context explicitly requires otherwise, the various steps may be performed in any desired order, and any applicable steps may be added and / or eliminated. Attached Figure Description

[0068] Figure 1 This is an illustrative EBSD plot in the L-LT plane, where grain boundaries are superimposed based on best-fit ellipses.

[0069] Figure 2a This is an illustrative EBSD generation diagram at T / 4 of the rolling plane (L-LT) of a conventional sheet metal product, showing the boundary with an orientation difference ≥ 15°.

[0070] Figure 2b This is an illustrative EBSD generation diagram at T / 4 of the rolling plane (L-LT) of a new sheet metal product, showing the boundary with an orientation difference ≥ 15°.

[0071] Figure 3a This is an illustrative EBSD generation diagram at T / 4 of the L-ST plane of a conventional sheet metal product, showing the boundary with an orientation difference ≥ 15°.

[0072] Figure 3b This is an illustrative EBSD generation diagram at T / 4 of the L-ST plane of the new sheet material product, showing the boundary with an orientation difference ≥ 15°. Detailed Implementation

[0073] Example 1

[0074] Ten batches of 7050 aluminum alloy sheet products were produced using industrial-size ingots. The ingots were 66 inches (1676 mm) wide prior to rolling. Six of these batches were produced using conventional hot rolling, with <10% of the total reduction coming from hot rolling passes in the long transverse (LT) direction, followed by rolling in the longitudinal (L) direction. The other four batches were produced by performing a large number of hot rolling passes in a first rolling direction, followed by several hot rolling passes in a second direction, which is typically transverse (e.g., perpendicular) to the first rolling direction. In this case, the first rolling direction corresponds to the long transverse direction, and the second direction corresponds to the longitudinal direction; however, it should be understood that the first rolling direction can also be the longitudinal direction and the second direction can also be the long transverse direction. Table 1 below provides the dimensions of the rolled sheet.

[0075] Table 1 – Data after rolling 1,2

[0076]

[0077] 1: The rolled specifications are reported in Table 1; due to subsequent processing (e.g., conventional stretching after solution heat treatment and quenching), the final specifications differ little from the rolled specifications.

[0078] 2: The widening percentage is calculated as follows: subtract the initial ingot size (66 inches or 1676 mm in this case) from the width of the rolled sheet, and then divide by the original ingot width.

[0079] After rolling, the thick-gauge plates were machined to T7451 temper, and then their mechanical properties were tested. The results are shown in Tables 2-4 below. The reported strength and elongation values ​​are averages of at least two samples. The reported fracture toughness values ​​are based on a single sample. Strength and elongation were measured according to ASTM E8 / E8M-21 and B557-15. Fracture toughness was measured according to ASTM E399-20a and B645-21.

[0080] Table 2a – Longitudinal (L) Characteristics (Imperial Units)

[0081]

[0082] Table 2b – Longitudinal (L) Characteristics (Metric Units)

[0083]

[0084] Table 3a – Long Lateral (LT) Characteristics (Imperial Units)

[0085]

[0086] Table 3b – Long Lateral (LT) Characteristics (Metric Units)

[0087]

[0088] Table 4a – Short Transverse (ST) Characteristics (Imperial Units)

[0089]

[0090] Table 4b – Short Lateral (ST) Characteristics (Metric Units)

[0091]

[0092] Table 5 below shows the differences in strength, elongation, and fracture toughness between the conventional alloy and the novel alloy. As shown, the novel alloy, which underwent extensive hot rolling in both the L and LT directions, achieved more isotropic strength, elongation, and fracture toughness properties, i.e., the percentage difference was closer to 0%.

[0093] Table 5 – Percentage Differences in L and LT Characteristics 3

[0094]

[0095] 3: Percentage difference is calculated as follows: L or LT characteristic minus LT or TL characteristic, and then divided by L or LT characteristic.

[0096] The electrical conductivity and fatigue crack growth rate (FCGR) of the plate from Example 1 were also measured, and the results are shown in Table 6 below. Fatigue crack growth tests were performed on intermediate tensile M(T) specimen geometries according to ASTM E647-15e1, with a specimen width of 6.3 in. (160 mm) and a specimen thickness of 0.197 in. (5 mm). The specimens were tested with a TL orientation and centered at the T / 4 thickness position of the plate. The tests were performed using a K-incrementing test procedure with a constant force amplitude or K gradient (C = 1.75 / in. [0.069 / mm]), a force ratio of R = 0.1, and a frequency of 2–15 Hz, in room temperature and laboratory air environments.

[0097] Table 6 – Electrical conductivity and fatigue crack growth rate (FCGR) characteristics

[0098]

[0099] ● The unit of da / dN is mm / cycle;

[0100] ● The unit of ΔK (Delta K) is MPa√m.

[0101] As shown, the electrical conductivity of the novel alloy is consistent with that of the conventional alloy. The FCGR properties of the novel alloy are significantly improved, especially at higher ΔK values. Table 7 below shows the improved FCGR properties of the novel alloy compared to the highest-performing conventional alloy at ΔK values ​​of 20, 25, and 30.

[0102] Table 7 – Comparison of fatigue crack propagation rate characteristics

[0103]

[0104] ● The unit of da / dN is mm / cycle;

[0105] ● The unit of ΔK (Delta K) is MPa√m.

[0106] As shown in Table 8 below, the improvement is even greater when the average crack propagation resistance of conventional alloys and novel alloys is taken into account.

[0107] Table 8 – Comparison of fatigue crack propagation rate characteristics

[0108]

[0109] ● The unit of da / dN is mm / cycle;

[0110] ● The unit of ΔK (Delta K) is MPa√m.

[0111] Based on the above microstructure evaluation procedure, the microstructures of some thick-gauge plates were obtained. For example... Figures 2a-2b and Figures 3a-3b As shown, the novel alloy achieves more equiaxed grains in the L-LT plane and also high aspect ratio grains in the L-ST plane. L-LT ARproj Awt Calculations confirm that grains are more isotropic in the L-LT plane. As shown in Table 9 below, conventional substrates achieved L-LT ARproj values ​​ranging from 3.11 to 3.57. Awt The new type of sheet material achieved an L-LTARproj of 1.18 to 1.98. Awt This indicates that the new sheet material achieves a more equiaxed grain structure in the rolling plane.

[0112] Table 9 – L:LT Projection Characteristics

[0113]

[0114] While various embodiments of the present disclosure have been described in detail, it will be apparent to those skilled in the art that modifications and adjustments can be made to these embodiments. However, it should be clearly understood that such modifications and adjustments are within the spirit and scope of the present disclosure.

Claims

1. A method comprising: (a) Hot rolling a heat-treatable aluminum alloy ingot into a final specification product, wherein the hot rolling comprises: (i) Performing a first hot rolling on the heat-treatable aluminum alloy ingot in a first rolling direction; and (ii) The heat-treatable aluminum alloy ingot is subjected to a second hot rolling in a second direction, wherein the second direction is different from the first direction; (iii) Optionally repeat steps (a)(i), (a)(ii), or both (a)(i) and (a)(ii); and (b) Process the final product to T tempering; The final sheet metal products are available in thicknesses ranging from 6.00 inches to 12.0 inches, and among them: (i) When the final specification product has a thickness of 6.01 inches to 6.50 inches, the rolled width of the final specification sheet product is at least 60% larger than the width of the heat-treatable aluminum alloy ingot; (ii) When the final specification product has a thickness of 6.51 inches to 7.00 inches, the rolled width of the final specification sheet product is at least 50% larger than the width of the heat-treatable aluminum alloy ingot; (iii) When the final specification product has a thickness of 7.01 inches to 7.50 inches, the rolled width of the final specification sheet product is at least 40% larger than the width of the heat-treatable aluminum alloy ingot; (iv) When the final specification product has a thickness of 7.51 inches to 8.00 inches, the rolled width of the final specification sheet product is at least 30% larger than the width of the heat-treatable aluminum alloy ingot; (iv) When the final specification product has a thickness of 8.01 inches to 12.00 inches, the rolled width of the final specification sheet product is at least 25% larger than the width of the heat-treatable aluminum alloy ingot; The final specifications are determined according to ANSI H35.

2.

2. The method according to claim 1, wherein the second hot rolling step occurs after the first hot rolling step.

3. The method of claim 1, wherein the second hot rolling step occurs before the first hot rolling step.

4. The method according to any one of the preceding claims, wherein the second rolling direction is transverse to the first rolling direction.

5. The method according to any one of the preceding claims, wherein the second rolling direction is perpendicular to the second rolling direction.

6. The method according to any one of the preceding claims, wherein the first hot rolling step comprises a plurality of hot rolling passes.

7. The method according to any one of the preceding claims, wherein the first hot rolling step comprises hot rolling the heat-treatable aluminum alloy ingot into an intermediate size.

8. The method according to any one of the preceding claims, wherein the second hot rolling step comprises a plurality of hot rolling passes.

9. The method according to any one of the preceding claims, wherein the second hot rolling step comprises hot rolling an intermediate specification product into a final specification product.

10. The method according to any one of the preceding claims, comprising completing all hot rolling passes of the first hot rolling step, and then completing all hot rolling passes of the second hot rolling step.

11. The method according to any one of claims 1 to 9, comprising completing a subset of the hot rolling passes of the first hot rolling step, and then completing all or a subset of the second hot rolling step.

12. The method of claim 11, further comprising additional hot rolling passes after the second hot rolling step to complete the first hot rolling step.

13. The method of claim 11, comprising all remaining hot rolling passes after the second hot rolling step to complete the first hot rolling step.

14. The method according to any one of the preceding claims, wherein the first rolling direction corresponds to the transverse direction of the final specification product, and wherein the second rolling direction corresponds to the longitudinal direction of the final specification product.

15. The method according to any one of claims 1 to 13, wherein the first rolling direction corresponds to the longitudinal direction of the final specification product, and wherein the second rolling direction corresponds to the transverse direction of the final specification product.

16. The method according to any one of the preceding claims, wherein the hot rolling step comprises: A third hot rolling process is performed in a third hot rolling direction, wherein the third hot rolling direction is different from both the first hot rolling direction and the second hot rolling direction.

17. The method of claim 16, wherein the third hot rolling direction corresponds to the 45° direction of the final specification product.

18. The method according to any one of claims 16 to 17, wherein the third hot rolling direction is completed before or after the first hot rolling step.

19. The method according to any one of claims 16 to 18, wherein the third hot rolling direction is completed before or after the second hot rolling step.

20. The method of any one of claims 1 to 19, wherein the final specification product has a thickness of 6.01 inches to 6.50 inches, and wherein the rolled sheet has a rolled width that is at least 65% larger than the width of the heat-treatable aluminum alloy ingot, or at least 70% larger than the width of the heat-treatable aluminum alloy ingot, or at least 75% larger than the width of the heat-treatable aluminum alloy ingot, or at least 80% larger than the width of the heat-treatable aluminum alloy ingot, or at least 85% larger than the width of the heat-treatable aluminum alloy ingot, or at least 90% larger than the width of the heat-treatable aluminum alloy ingot, or at least 95% larger than the width of the heat-treatable aluminum alloy ingot, or at least 100% larger than the width of the heat-treatable aluminum alloy ingot.

21. The method of any one of claims 1 to 19, wherein the final specification product has a thickness of 6.51 inches to 7.00 inches, and wherein the rolled sheet has a rolled width that is at least 55% larger than the width of the heat-treatable aluminum alloy ingot, or at least 60% larger than the width of the heat-treatable aluminum alloy ingot, or at least 65% larger than the width of the heat-treatable aluminum alloy ingot, or at least 70% larger than the width of the heat-treatable aluminum alloy ingot, or at least 75% larger than the width of the heat-treatable aluminum alloy ingot, or at least 80% larger than the width of the heat-treatable aluminum alloy ingot, or at least 85% larger than the width of the heat-treatable aluminum alloy ingot, or at least 90% larger than the width of the heat-treatable aluminum alloy ingot, or at least 95% larger than the width of the heat-treatable aluminum alloy ingot, or at least 100% larger than the width of the heat-treatable aluminum alloy ingot.

22. The method of any one of claims 1 to 19, wherein the final specification product has a thickness of 7.01 inches to 7.50 inches, and wherein the rolled sheet has a rolled width at least 45% greater than the width of the heat-treatable aluminum alloy ingot, or at least 50% greater than the width of the heat-treatable aluminum alloy ingot, or at least 55% greater than the width of the heat-treatable aluminum alloy ingot, or at least 60% greater than the width of the heat-treatable aluminum alloy ingot, or greater than the width of the heat-treatable aluminum alloy ingot. At least 65%, or at least 70% larger than the width of the heat-treatable aluminum alloy ingot, or at least 75% larger than the width of the heat-treatable aluminum alloy ingot, or at least 80% larger than the width of the heat-treatable aluminum alloy ingot, or at least 85% larger than the width of the heat-treatable aluminum alloy ingot, or at least 90% larger than the width of the heat-treatable aluminum alloy ingot, or at least 95% larger than the width of the heat-treatable aluminum alloy ingot, or at least 100% larger than the width of the heat-treatable aluminum alloy ingot.

23. The method of any one of claims 1 to 19, wherein the final specification product has a thickness of 7.51 inches to 8.00 inches, and wherein the rolled sheet has a rolled width at least 35% greater than the width of the heat-treatable aluminum alloy ingot, or at least 40% greater than the width of the heat-treatable aluminum alloy ingot, or at least 45% greater than the width of the heat-treatable aluminum alloy ingot, or at least 50% greater than the width of the heat-treatable aluminum alloy ingot, or at least 55% greater than the width of the heat-treatable aluminum alloy ingot, or greater than the width of the heat-treatable aluminum alloy ingot. At least 60%, or at least 65% larger than the width of the heat-treatable aluminum alloy ingot, or at least 70% larger than the width of the heat-treatable aluminum alloy ingot, or at least 75% larger than the width of the heat-treatable aluminum alloy ingot, or at least 80% larger than the width of the heat-treatable aluminum alloy ingot, or at least 85% larger than the width of the heat-treatable aluminum alloy ingot, or at least 90% larger than the width of the heat-treatable aluminum alloy ingot, or at least 95% larger than the width of the heat-treatable aluminum alloy ingot, or at least 100% larger than the width of the heat-treatable aluminum alloy ingot.

24. The method of any one of claims 1 to 19, wherein the final specification product has a thickness of 8.01 inches to 12.00 inches, and wherein the rolled sheet has a rolled width at least 30% greater than the width of the heat-treatable aluminum alloy ingot, or at least 35% greater than the width of the heat-treatable aluminum alloy ingot, or at least 40% greater than the width of the heat-treatable aluminum alloy ingot, or at least 45% greater than the width of the heat-treatable aluminum alloy ingot, or at least 50% greater than the width of the heat-treatable aluminum alloy ingot, or at least 55% greater than the width of the heat-treatable aluminum alloy ingot, or at least 30% greater than the width of the heat-treatable aluminum alloy ingot, or at least 35 ... The width of the processed aluminum alloy ingot is at least 60% greater, or at least 65% greater than the width of the heat-treatable aluminum alloy ingot, or at least 70% greater than the width of the heat-treatable aluminum alloy ingot, or at least 75% greater than the width of the heat-treatable aluminum alloy ingot, or at least 80% greater than the width of the heat-treatable aluminum alloy ingot, or at least 85% greater than the width of the heat-treatable aluminum alloy ingot, or at least 90% greater than the width of the heat-treatable aluminum alloy ingot, or at least 95% greater than the width of the heat-treatable aluminum alloy ingot, or at least 100% greater than the width of the heat-treatable aluminum alloy ingot.

25. The method of claim 24, wherein the final specification product has a thickness of not more than 11.5 inches (292.1 mm), or not more than 11.0 inches (279.4 mm), or not more than 10.5 inches (266.7 mm), or not more than 10.0 inches (254 mm).

26. The method according to any one of the preceding claims, wherein the final specification product achieves an ARproj of no more than 2.

75. Awt .

27. The method of claim 26, wherein the final specification product achieves an ARproj of no greater than 2.5, or no greater than 2.4, or no greater than 2.3, or no greater than 2.2, or no greater than 2.1, or no greater than 2.0, or no greater than 1.9, or no greater than 1.8, or no greater than 1.7, or no greater than 1.6, or no greater than 1.5, or no greater than 1.4, or no greater than 1.3, or no greater than 1.

2. Awt .

28. The method according to any one of the preceding claims, wherein the final specification product achieves longitudinal tensile yield strength (TYS-L) and long transverse tensile yield strength (TYS-LT), and wherein the final specification sheet product is isotropic in strength, wherein the absolute value of [(TYS-L) minus (TYS-LT)] divided by (TYS-L) is not greater than 5%.

29. The method according to claim 28, wherein the absolute value of [(TYS-L) minus (TYS-LT)] divided by (TYS-L) is not greater than 4.5%, or not greater than 4.0%, or not greater than 3.5%, or not greater than 3.0%, or not greater than 2.5%, or not greater than 2.0%.

30. The method according to any one of the preceding claims, wherein the final specification product achieves longitudinal elongation (Elong.-L) and long transverse elongation (Elong.-LT), and wherein the final specification sheet product is isotropic in elongation, wherein the absolute value of [(Elong.-L) minus (Elong.-LT)] divided by (Elong.-L) is not greater than 25%.

31. The method according to claim 30, wherein the absolute value of [(Elong.-L) minus (Elong.-LT)] divided by (Elong.-L) is not greater than 20%, or not greater than 15%, or not greater than 10%, or not greater than 8%, or not greater than 6%.

32. The method according to any one of the preceding claims, wherein the final specification product achieves LT K. IC Fracture toughness and TL K IC Fracture toughness, and wherein the final specification sheet product is isotropic in fracture toughness, wherein [(LT K IC Subtract (TL K) IC Divide by (LT K) IC The absolute value of ) is no greater than 20%.

33. The method of claim 32, wherein [(LT K IC Subtract (TL K) IC Divide by (LT K) IC The absolute value of ) is not greater than 18%, or not greater than 16%, or not greater than 14%, or not greater than 12%, or not greater than 10%, or not greater than 8%, or not greater than 6%, or not greater than 4%, or not greater than 2%.

34. The method according to any one of the preceding claims, wherein when ΔK is 20, the final specification product achieves at least a 2% improvement in fatigue crack propagation resistance compared to the baseline product, wherein the baseline product has equivalent composition, tempering and specifications, and wherein the baseline product is produced by hot rolling only in the longitudinal direction.

35. The method of claim 34, wherein when ΔK is 20, the final specification product achieves an improvement of at least 4%, or at least 6%, or at least 8%, or at least 10%, or at least 12%, or at least 14%, or at least 16% in fatigue crack propagation resistance compared to the baseline product.

36. The method according to any one of the preceding claims, wherein when ΔK is 25, the final specification product achieves at least a 5% improvement in fatigue crack propagation resistance compared to the baseline product, wherein the baseline product has an equivalent composition, tempering and specification, and wherein the baseline product is produced by hot rolling only in the longitudinal direction.

37. The method of claim 36, wherein, when ΔK is 25, the final specification product achieves an improvement in fatigue crack propagation resistance of at least 10%, or at least 15%, or at least 20%, or at least 22%, or at least 24%, or at least 26%, or at least 28%, or at least 30%, or at least 32%, or at least 34% compared to the baseline product.

38. The method according to any one of the preceding claims, wherein when ΔK is 30, the final specification product achieves at least a 5% improvement in fatigue crack propagation resistance compared to the baseline product, wherein the baseline product has equivalent composition, tempering and specifications, and wherein the baseline product is produced by hot rolling only in the longitudinal direction.

39. The method of claim 38, wherein, when ΔK is 30, compared to the baseline product, the final specification product achieves an improvement in fatigue crack propagation resistance of at least 10%, or at least 15%, or at least 20%, or at least 22%, or at least 24%, or at least 26%, or at least 28%, or at least 30%, or at least 32%, or at least 34%, or at least 36%, or at least 38%, or at least 40%, or at least 42%, or at least 44%.

40. The method according to any one of the preceding claims, wherein the heat-treatable aluminum alloy is selected from the group consisting of: 2xxx, 6xxx, 7xxx and 8xxx aluminum alloys.

41. The method according to any one of the preceding claims, wherein the heat-treatable aluminum alloy is a 7xxx aluminum alloy.

42. The method of claim 41, wherein the 7xxx aluminum alloy is selected from the group consisting of: 7050, 7150, 7050A, 7040, 7140, 7085, 7185, 7065, 7036, 7136, 7081 and 7181.

43. The method according to claim 41, wherein the 7xxx aluminum alloy is 7050.

44. The method according to claim 40, wherein the 2xxx aluminum alloy is a lithium-containing 2xxx aluminum alloy.

45. The method according to claim 44, wherein the 2xxx aluminum alloy is 2050 or 2195.

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