HIGH-PERFORMANCE 5000-SERIES ALUMINUM ALLOYS AND METHODS FOR MAKING AND USING THEM

Abstract

5000 series aluminum wrought alloys with high strength, high formability, excellent corrosion resistance, and friction-stir weldability, and methods of making those alloys.

Claims

1. An aluminum alloy comprising: about 3% to about 5% by weight magnesium; about 0.1% to about 4% by weight zinc; about 0.6% to about 1% by weight manganese; about 0.1% to about 0.3% by weight chromium; about 0.4% to about 0.8% by weight zirconium; aluminum as the remainder; and a dispersion of coherent Al.sub.3Zr nanoscale precipitates with an Ll.sub.2 crystal structure in an aluminum matrix, the Al.sub.3Zr nanoscale precipitates having an average radius of no more than about 20 nm and having an average number density of no less than about 5×10.sup.20 per m.sup.3.

2. The aluminum alloy of claim 1, further comprising scandium at a concentration of no more than about 0.15% by weight.

3. The aluminum alloy of claim 1, further comprising copper at a concentration of no more than about 1% by weight.

4. The aluminum alloy of claim 1, further comprising a dispersion of the incoherent Al.sub.6Mn dispersoids having an average radius in the range of about 50 nm to about 200 nm.

5. The aluminum alloy of claim 1, further comprising a dispersion of Al.sub.12Mn, Al.sub.7Cr or Al.sub.45Cr.sub.7 intermetallic phases in the range of about 50 nm to about 800 nm in size.

6. The aluminum alloy of claim 5, further comprising a dispersion of the incoherent Al.sub.6Mn dispersoids having an average radius in the range of about 50 nm to about 200 nm.

7. The aluminum alloy of claim 1, wherein the alloy has mechanical strength comparable to commercial high-strength AA7039-T6 and AA7075-T6 alloys.

8. The aluminum alloy of claim 1, wherein the alloy has the same or better corrosion resistance compared to commercial AA5083 alloy.

9. The aluminum alloy of claim 1, wherein the alloy has better creep resistance compared to commercial AA5083 alloy at a temperature range from about 25° C. to about 450° C.

10. The An aluminum alloy of claim 1, wherein the alloy is weldable by a gas welding method.

11. The aluminum alloy of claim 10, wherein the gas welding method is selected from a group consisting of Metal Inert Gas (MIG), Tungsten Inert Gas (TIG), and a friction-stir welding method.

12. The aluminum alloy of claim 1, wherein the alloy maintains high room temperature strength after exposure at about 375° C. for at least about 300 hours.

13. The aluminum alloy of claim 1, wherein the alloy comprises about 3.5% to 4% by weight magnesium and about 0.85% to 1.2% by weight zinc.

14. The aluminum alloy of claim 13, wherein the alloy further comprises about 0.5% to about 0.7% by weight zirconium.

15. The aluminum alloy of claim 14, further comprising about 0.1% to about 1% by weight copper.

16. The aluminum alloy of claim 14, further comprising about 0.08% to about 0.12% by weight scandium.

17. The aluminum alloy of claim 16, further comprising about 0.1% to about 1% by weight copper.

18. The aluminum alloy of claim 1, wherein the alloy further comprises about 3.3% to about 4% by weight magnesium and about 3.5% to about 4.2% by weight zinc.

19. The aluminum alloy of claim 18, wherein the alloy further comprises about 0.5% to about 0.7% by weight zirconium.

20. The aluminum alloy of claim 19, further comprising about 0.1% to about 1% by weight copper.

21. The aluminum alloy of claim 19, further comprising about 0.08% to about 0.12% by weight scandium.

22. The aluminum alloy of claim 21, further comprising about 0.1% to about 1% by weight copper.

23. A method of making the aluminum alloy of claim 1, the method comprising: melting an alloy mixture in a temperature range of about 750° C. to about 950° C.; casting the melted alloy mixture with a high solidification cooling rate that is above about 50° C./s; and after the casting step, aging the cast alloy at a temperature in a range of about 275° C. to about 475° C. for about 2 hours to about 72 hours.

24. The method of claim 23, wherein the aging step comprises aging the cast alloy at a temperature in a range of about 350° C. to about 475° C. for about 2 hours to about 72 hours.

25. The method of claim 23, wherein the aging step comprises: aging the cast alloy at a temperature in a range of about 275° C. to about 375° C. for about 2 hours to about 24 hours; and then aging the cast alloy at a temperature in a range of about 375° C. to about 475° C. for about 1 hour to about 24 hours.

26. The method of claim 23, wherein the aging step comprises aging the cast alloy at a temperature in a range of about 350° C. to about 450° C. for about 24 hours to about 72 hours.

27. The method of claim 23, wherein the casting step is performed using a casting method selected from a group consisting of squeeze casting, twin-belt casting, twin-roll casting, strip casting, and bar casting.

28. The method of claim 23, further comprising hot rolling the cast alloy after the casting step and before aging step.

29. The method of claim 23, further comprising cold rolling the cast alloy either before or after the aging step to fabricate cast articles into shape.

30. The method of claim 23, further comprising: after the aging step, additionally aging the cast alloy at a temperature in a range of about 120° C. to about 200° C. for about 8 hours to about 72 hours.

31. A cast aluminum component comprising the alloy of claim 1.

32. The aluminum component of claim 31, the component being selected from a group consisting of automotive body panels, boat or ship body structures, storage tanks, pressure vessels, and vessels for land or marine structures.

Description

BRIEF DESCRIPTION OF FIGURES

[0034] FIGS. 1A and 1B show scanning electron microscope images of the microstructure of an example alloy.

[0035] FIG. 2 graphs microhardness as a function of time for an example alloy aged at 375° C. for 14 days.

[0036] FIG. 3 illustrates the effect of one-step versus two step-aging at high temperature (temperature T1 or T2) in the range of 300-475° C. for an example alloy.

[0037] FIG. 4 shows the effect of an optional low temperature aging step on the microhardness of an example alloy.

DETAILED DESCRIPTION OF INVENTION

[0038] A series of high performance 5000 series aluminum wrought alloys with high strength, high formability, high corrosion resistance, and excellent creep resistance are disclosed.

[0039] The high strength at room temperature for the disclosed alloys is believed to related to: i) maximizing the matrix strength through solid solution strengthening utilizing alloying elements; and ii) further strengthening the matrix through dispersion hardening and precipitation hardening.

[0040] The solid solution strengthening in the disclosed alloys is associated with the alloying elements such as magnesium, zinc, chromium, manganese, and copper to create a solid-solution strengthening effect, and achieved through designed composition and specific heat treatment condition.

[0041] The precipitation hardening and dispersion hardening in the disclosed alloys are associated with: a) the precipitation of coherent Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) with Ll.sub.2 crystal structure and an average radius of no more than about 20 nm, such as in the range of 3-20 nm and with an average number density of no less than about 5×10.sup.20/m.sup.3; b) the precipitation of incoherent Al.sub.6Mn dispersoids with a an average radius in the range of about 50nm to about 200 nm; c) the precipitation of coherent Mg—Zn G. P. zones and intermediate phase (precursor of the equilibrium MgZn.sub.2, so called or η′ or M′ phase) in alloys with high Zn/Mg ratio, having an average radius of about 1 nm to about 5 nm; d) the precipitation of coherent Al—Mg—Zn G. P. zones and intermediate phase (precursor of the equilibrium Mg.sub.3Zn.sub.3Al.sub.2, so called T′ phase) in alloy with low Zn/Mg ratio, having an average radius of about 1 nm to about 5 nm; and e) the formation of Al.sub.12Mn, Al.sub.7Cr (or Al.sub.45Cr.sub.7) intermetallic phases in the range of about 50 nm to about 800 nm in size. The presence of intermetallic phases and nano-precipitates within the grains impose a strong pinning effect against dislocation motions at ambient temperature.

[0042] The high strength and excellent creep resistance at elevated temperatures for the disclosed alloys are associated with the presence of: a) coherent coarsening-resistant Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) with Ll.sub.2 crystal structure and an average radius of no more than about 20 nm, such as in the range of 3-20 nm and with an average number density of no less than about 5×10.sup.20/m.sup.3; b) incoherent coarsening-resistant Al.sub.6Mn dispersoids with an average radius in the range of about 50 nm to about 200 nm; and c) Al.sub.12Mn, Al.sub.7Cr (or Al.sub.45Cr.sub.7) intermetallic phases in the range of about 50 nm to about 800 nm in size. The presence of thermally-stable intermetallic phases and nano-precipitates within the grains create a strong pinning force against dislocation motions at elevated temperatures, which translates into higher strength at elevated temperatures as high as about 400° C. (752° F.) for long exposure times for the disclosed alloys.

[0043] Some of the advantages of the disclosed alloys are that they can be fabricated via low cost casting methods such as squeeze casting, twin-belt (roll) casting, and strip (bar) casting.

[0044] Another advantage of these alloys is the low cost of raw material, which results in a low alloy cost.

[0045] The presence of zinc and copper in the alloy results in formation of AlMgZn and Al.sub.2CuMg phases within the grains and prevents formation of continuous Al—Mg phase along grain boundaries. It leads to improved corrosion resistance of the disclosed alloys.

[0046] The high average number density of no less than about 5×10.sup.20/m.sup.3 of Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) nano-precipitates, having the Ll.sub.2 crystal structure and an average radius of no more than about 20 nm, such as in the range of 3-20 nm, is produced by super-saturation of the aluminum matrix solid solution from solutes through high cooling rates obtained from casting methods and subsequent precipitation. The presence of high cooling rates is necessary to obtain outstanding properties such as strength and creep resistance at ambient and elevated temperatures.

[0047] The disclosed 5000 aluminum alloys provide light weight, low cost, high strength, high creep and aging resistance, high corrosion resistance, and friction-stir weldability. These alloys are thermally stable, that is minimal drop in hardness after exposure for many hours, in the temperature range of about 25° C. to about 400° C.

[0048] The aforementioned properties are obtained, for example, for the disclosed alloys that contain: [0049] about 3% to about 5% by weight magnesium, [0050] about 0.5% to about 4% by weight zinc, [0051] about 0.6% to about 1% by weight manganese, [0052] about 0.1% to about 0.3% by weight chromium, [0053] about 0.25% to about 0.8% by weight zirconium, [0054] 0 to about 0.15% by weight scandium, [0055] Up to about 1% by weight copper, and [0056] aluminum as the remainder.

[0057] The excellent creep resistance of the disclosed alloys results from two main strengthening mechanisms: the intermetallic dispersion hardening and nano-precipitation, which create barriers to dislocation motions (i.e. glide and climb mechanisms) at elevated temperatures.

[0058] The intermetallic dispersion hardening relies on the formation of dispersed intermetallic phase within the grains during solidification and during heat treatment. About 0.6% to about 1% by weight manganese, about 0.1% to about 0.3% by weight chromium, about 0.25% to about 0.8% by weight zirconium, and about 0 to about 0.15% by weight scandium is utilized to form a fine dispersion of Al.sub.6Mn, Al.sub.12Mn, Al.sub.45Cr.sub.7, and Al.sub.3(Sc,Zr) intermetallic phases within the grains. These phases are formed during solidification and during subsequent heat treatment processes. The volume fraction and size of the intermetallic phase depends on the casting condition, solidification (cooling) rate, concentration of elements, and the specific heat treatment conditions. FIGS. 1A and 1B show a distribution of such intermetallic phases in a disclosed aluminum alloy (Al—4.3Mg—1.1Zn—0.8Mn—0.20Cr—0.7Zr % by weight). The microstructure is substantially homogenous with a fine uniform distribution of intermetallic particles Al.sub.3Zr (or Al.sub.3(Zr,Sc) if the alloy further includes scandium at a concentration of no more than about 0.15% by weight), Al.sub.6Mn, and Al.sub.12Mn within the grains.

[0059] The nano-precipitation hardening relies on the formation of nano-precipitates in the aluminum matrix through specific heat treatment conditions. About 0.5% to about 4% by weight zinc, about 3.5% to about 5% by weight magnesium, up to about 1% by weight copper, about 0.25% to about 0.80% by weight zirconium, and 0 to about 0.15% by weight scandium create a high number density of nano-precipitates, in the order of about 5×10.sup.20 m.sup.−3 to about 9×10.sup.21 m.sup.−3, uniformly distributed in the matrix.

[0060] The nano-precipitates are in two categories: i) the low-temperatures nano-precipitates, thermally stable in the range of about 20° C. to about 180° C., consisting of coherent Mg—Zn G. P. zones and intermediate phase (precursor of the equilibrium MgZn.sub.2, so called η′ or M′ phase) in alloys with high Zn/Mg ratio, having an average radius of about 1 nm to about 5 nm, and the precipitation of coherent Al—Mg—Zn G. P. zones and intermediate phase (precursor of the equilibrium Mg.sub.3Zn.sub.3Al.sub.2, so called T′ phase) in alloy with low Zn/Mg ratio, having an average radius of about 1 nm to about 5 nm; and ii) the high temperature nano-precipitates, thermally stable in the range of about 20° C. to about 400° C., consisting of coherent Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) with Ll.sub.2 crystal structure and an average radius of no more than about 20 nm, such as in the range of 3-20 nm and with an average number density of no less than about 5×10.sup.20/m.sup.3. The volume fraction, diameter, and lattice mismatch of Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) nano-precipitates depend on the concentration of Zr and Sc, and the specific heat treatment conditions.

[0061] The specific concentration of alloying elements and heat treatment conditions are necessary to create the desired microstructure with desired diameter and volume fraction of intermetallic phases and nano-precipitates. Generally, the disclosed alloys after optimal processing contain about 0.3% to about 0.8% by volume fraction Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) nano-precipitates.

[0062] To activate the strengtheners and achieve outstanding mechanical properties, the cast articles must have specific chemical compositions and heat treatments. These conditions are designed to maximize the strengthening effects through optimized formation of solid solution, nano-precipitates and intermetallic phases.

[0063] The high strength of disclosed alloys is achieved when using a T5 temper consisting of aging at about 350° C. to about 475° C. for about 24 hours to about 72 hours. The unique composition and the corresponding heat treatment allow nearly full precipitation of Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) nano-precipitates with high average number density of no less than about 5×10.sup.20/m.sup.3 and average radius of no more than about 20 nm, such as in the range of 3-20, while maintaining strength obtained through solid solution. The strength of invented alloys with specific composition and casting condition can be further increased by following an optional aging step. Following the first step aging at about 350° C. to about 475° C. for about 24 hours to about 72 hours, the optional step aging is conducted at temperatures about 120° C. to about 200° C. for about 8 hours to about 72 hours. The unique composition and the corresponding optional step aging allow uniform distribution of low-temperature nano-precipitates which results in higher strength. Table 1 shows a comparison of examples of presently disclosed alloys labeled M1 (Al—4.0Mg—4.0Zn—0.8Mn—0.20Cr—0.5Zr—0.1Sc % by weight) and M2 (Al—4.0Mg—4.0Zn—0.8Mn—0.20Cr—0.7Zr % by weight) with two commercial 5000 alloys, namely 5454 and 5083. The testing temperature for all alloys present in the table is at room temperature. The example alloys are aged to optimal condition prior to testing. The table shows significant improvement in mechanical properties of the disclosed alloys (i.e. strength, microhardness) compared to the commercial alloys.

TABLE-US-00001 TABLE 1 Alloys 5083  M1 5454  M2 Temper H34 T5 H34 T5 Yield (MPa) 280 349* 241 333* UTS (MPa) 345 554* 303 524* Ductility (%)  7 —**  16 —** Hardness (HV) 104 135   91 127  Corrosion resistance Good Good Good Good Friction-stir weldability Good Good Good Good *Values were measured in compression mode **Values were not measured

[0064] The thermal stability properties of the disclosed alloys is believed to be related to the presence of: a) thermally stable solid-solution strengthening; b) heat resistant Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) with Ll.sub.2 crystal structure and an average radius of no more than about 20 nm, such as in the range of 3-20 nm and with an average number density of no less than about 5×10.sup.20/m.sup.3; c) incoherent Al.sub.6Mn dispersoids with an average radius in the range of about 50 nm to about 200 nm; and d) incoherent Al.sub.12Mn and Al.sub.7Cr (or Al.sub.45Cr.sub.7) intermetallic phases in the range of about 50 nm to about 800 nm in size. The disclosed alloys are aging resistant up to about 400° C. The temperature range for aging resistance depends on the specific chemistry of the alloy and the heat treatment condition. Herein, the aging resistance is described as the retained room temperature strength after exposure to high temperature for 1000 hours. FIG. 2 shows the aging resistance of an example alloy (Al—4.3Mg—1.1Zn—08.Mn—0.20Cr—0.7Zr % by weight) at 375° C. The alloy is heat treated to optimum condition prior to exposure to 375° C. The results show no drop in microhardness values after exposure to 375° C. for two weeks.

[0065] The disclosed alloys may be produced in the form of plates through continuous casting routes such as twin-roll (twin-belt) casting. The high cooling rates (above about 50° C./s) achieved through these methods allow maximizing the content of solute atoms in the solid solution, which is crucial to obtain optimal mechanical properties after precipitation. The casting temperature is in the range of about 750° C. to about 950° C. (1382-1742° F.) (and preferably of about 800° C. to about 950° C.). After casting, the wrought product is aged at temperature in the range of about 350° C. to about 475° C. for about 24 hours to about 72 hours followed by optional aging at about 120° C. to about 200° C. for about 8 hours to about 72 hours to achieve optimal mechanical properties.

[0066] The disclosed alloys may be heat treated in one or two-step aging processes at high temperature. The two-step aging is performed on cast alloys to maximize room-temperature mechanical properties such as hardness, strength, ductility, and fracture toughness. While the first step aging at lower aging temperature creates a high number density of nuclei due to the higher chemical driving force, the second step aging at higher temperature accelerates the kinetics of precipitate growth to achieve optimal strength. For the one-step aging process, the cast article can be aged at temperature in the range of about 275° C. to about 475° C. for about 2 hours to about 72 hours (preferably in the range of about 350° C. to about 475° C. for about 24 hours to about 72 hours) to achieve optimal properties. For the two-step aging process, in the first step, the cast article can be aged at temperature range of about 330° C. to about 375° C. for about 2 hours to about 24 hours followed by the second step aging at about 425° C. to about 475° C. for about 1 hour to about 24 hours. The effect of two-step aging versus one-step aging is presented in FIG. 3 for an example disclosed alloy (Al—4.0Mg—1.0Zn—0.8Mn—0.20Cr—0.5Zr—0.1Sc % by weight, with T1=300° C. and T2=400° C.). A noticeable increase in microhardness values is observed for the alloy aged by the two-step aging process.

[0067] The disclosed alloys alloy can be further heat treated optimally at low-temperature after the high temperature one-step or two-step aging process. The heat treatment will be conducted at low-temperatures in the range of about 120° C. to about 200° C. for about 8 hours to about 72 hours. This optional step-aging at low temperature is to further improve the corrosion resistance and mechanical properties such as hardness, strength, ductility, and fracture toughness. The effect of the optional aging step for an example disclosed alloy (Al—4.0Mg—4.0Zn—0.8Mn—0.20Cr—0.7Zr by weight) is presented in FIG. 4. For this alloy, the microhardness is increased more than 24% after aging for about 24 hours to about 48 hours at an aging temperature in the range of about 120° C. to about 200° C. Also Table 2 shows the effect of the optional step aging on the example alloy M2. The properties of two high strength 7000 commercial alloys, namely AA7039 and AA7075, are presented for comparison. The microhardness of the alloy was increase from 127 HV to 157 HV, a 24% improvement after final step aging.

TABLE-US-00002 TABLE 2 Alloys M2 7039  7075  Temper T6 T64 T651 Yield (MPa) 408* 380 503 UTS (MPa) 546* 450 572 Ductility (%) —**  13  9 Hardness (HV) 157  153 175 Corrosion resistance Good Bad Bad Friction-stir weldability Good Bad Bad *Values were measured in compression mode **Values were not measured

[0068] A disclosed aluminum magnesium alloy has high strength at room and elevated temperatures, high creep resistance, high corrosion resistance, and good weldability, and comprises: [0069] about 3% to about 5% by weight magnesium, [0070] about 0 to about 4% by weight zinc, [0071] about 0.6 to about 1% by weight manganese, [0072] about 0.1% to about 0.3% by weight chromium, [0073] about 0.25% to about 0.8% by weight zirconium, and [0074] aluminum as the remainder.

[0075] A disclosed alloy can further comprise scandium at a concentration of up to about 0.15% by weight.

[0076] A disclosed alloy can further comprise copper at a concentration of up to about 1% by weight.

[0077] In certain embodiments the disclosed alloys lack scandium.

[0078] A disclosed alloy can further comprise about 3.5% to about 4% by weight magnesium and about 0.85% to about 1.2% by weight zinc.

[0079] A disclosed alloy can further comprise about 3.3% to about 4% by weight magnesium and about 3.5% to about 4.2% by weight zinc.

[0080] A disclosed alloy can further comprise about 3.5% to about 4% by weight magnesium, about 0.85% to about 1.2% by weight zinc, and about 0.5% to about 0.7% by weight zirconium.

[0081] A disclosed alloy can further comprise about 3.3% to about 4% by weight magnesium, about 3.5% to about 4.2% by weight zinc, and about 0.5% to about 0.7% by weight zirconium.

[0082] A disclosed alloy can further comprise about 3.5% to about 4% by weight magnesium, about 0.85% to about 1.2% by weight zinc, about 0.5% to about 0.7% by weight zirconium, and about 0.1% to about 1% by weight copper.

[0083] A disclosed alloy can further comprise about 3.3% to about 4% by weight magnesium, about 3.5% to about 4.2% by weight zinc, about 0.5% to about 0.7% by weight zirconium, and about 0.1% to about 1% by weight copper.

[0084] A disclosed alloy can further comprise about 3.5% to about 4% by weight magnesium, about 0.85% to about 1.2% by weight zinc, about 0.5% to about 0.7% by weight zirconium, and about 0.08% to about 0.12% by weight scandium.

[0085] A disclosed alloy can further comprise about 3.3% to about 4% by weight magnesium, about 3.5% to about 4.2% by weight zinc, about 0.5% to about 0.7% by weight zirconium, and about 0.08% to about 0.12% by weight scandium.

[0086] A disclosed alloy can further comprise about 3.5% to about 4% by weight magnesium, about 0.85% to about 1.2% by weight zinc, about 0.5% to about 0.7% by weight zirconium, about 0.08% to about 0.12% by weight scandium, and about 0.1% to about 1% by weight copper.

[0087] A disclosed alloy can further comprise about 3.3% to about 4% by weight magnesium, about 3.5% to about 4.2% by weight zinc, about 0.5% to about 0.7% by weight zirconium, about 0.08% to about 0.12% by weight scandium, and about 0.1% to about 1% by weight copper.

[0088] A disclosed alloy can comprise a dispersion of coherent Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) with Ll.sub.2 crystal structure with an average radius of no more than about 20 nm, such as in the range of 3-20 nm and with an average number density of no less than about 5×10.sup.20/m.sup.3.

[0089] A disclosed alloy can comprise a dispersion of the incoherent Al.sub.6Mn dispersoids with an average radius in the range of about 50 nm to about 200 nm.

[0090] A disclosed alloy can comprise a dispersion of coherent Mg—Zn G. P. zones and intermediate phase (precursor of the equilibrium MgZn.sub.2, so called η′ or M′ phase) in alloys with high Zn/Mg ratio, having an average radius of about 1 nm to about 5 nm.

[0091] A disclosed alloy can comprise a dispersion of coherent Al—Mg—Zn G. P. zones and intermediate phase (precursor of the equilibrium Mg.sub.3Zn.sub.3Al.sub.2, so called T′ phase) in alloy with low Zn/Mg ratio, having an average radius of about 1 nm to about 5 nm.

[0092] A disclosed alloy can comprise a dispersion of Al.sub.12Mn, Al.sub.7Cr (or Al.sub.45Cr.sub.7) intermetallic phases in the range of about 50 nm to about 800 nm in size.

[0093] A disclosed alloy can comprise a dispersion of coherent Al.sub.2CuMg G. P. zones and intermediate phase, so called θ′ in alloys with Cu content, having an average radius of about 1 nm to about 5 nm.

[0094] A disclosed alloy can comprise a dispersion of coherent Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) with Ll.sub.2 crystal structure with an average radius of no more than about 20 nm, such as in the range of 3-20 nm and with an average number density of no less than about 5×10.sup.20/m.sup.3, a dispersion of the incoherent Al.sub.6Mn dispersoids with an average radius in the range of about 50 nm to about 200 nm, and a dispersion of Al.sub.12Mn, Al.sub.7Cr (or Al.sub.45Cr.sub.7) intermetallic phases in the range of about 50 nm to about 800 nm in size.

[0095] A disclosed alloy can comprise a dispersion of coherent Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) with Ll.sub.2 crystal structure with an average radius of no more than about 20 nm, such as in the range of 3-20 nm and with an average number density of no less than about 5×10.sup.20/m.sup.3, a dispersion of the incoherent Al.sub.6Mn dispersoids with an average radius in the range of about 50 nm to about 200 nm, a dispersion of Al.sub.12Mn, Al.sub.7Cr (or Al.sub.45Cr.sub.7) intermetallic phases in the range of about 50 nm to about 800 nm in size, and a dispersion of coherent Mg—Zn G. P. zones and intermediate phase (precursor of the equilibrium MgZn.sub.2, η′ or M′ phase) in alloys with high Zn/Mg ratio, having an average radius of about 1 nm to about 5 nm.

[0096] A disclosed alloy can comprise a dispersion of coherent Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) with Ll.sub.2 crystal structure with an average radius of no more than about 20 nm, such as in the range of 3-20 nm and with an average number density of no less than about 5×10.sup.20/m.sup.3, a dispersion of the incoherent Al.sub.6Mn dispersoids with an average radius in the range of about 50 nm to about 200 nm, a dispersion of Al.sub.12Mn, Al.sub.7Cr (or Al.sub.45Cr.sub.7) intermetallic phases in the range of about 50 nm to about 800 nm in size, and a dispersion of coherent Al—Mg—Zn G. P. zones and intermediate phase (precursor of the equilibrium Mg.sub.3Zn.sub.3Al.sub.2, T′ phase) in alloy with low Zn/Mg ratio, having an average radius of about 1 nm to about 5 nm.

[0097] A disclosed alloy can comprise copper at the concentration up to about 1% by weight and a dispersion of coherent Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) with Ll.sub.2 crystal structure with an average radius of no more than about 20 nm, such as in the range of 3-20 nm and with an average number density of no less than about 5×10.sup.20/m.sup.3, a dispersion of the incoherent Al.sub.6Mn dispersoids with an average radius in the range of about 50 nm to about 200 nm, a dispersion of Al.sub.12Mn, Al.sub.7Cr (or Al.sub.45Cr.sub.7) intermetallic phases in the range of about 50 nm to about 800 nm in size, a dispersion of coherent Mg—Zn G. P. zones and intermediate phase (precursor of the equilibrium MgZn.sub.2, η′ or M′ phase) in alloys with high Zn/Mg ratio, having an average radius of about 1 nm to about 5 nm, and a dispersion of coherent Al.sub.2CuMg G. P. zones and intermediate phase, θ′ in alloys with Cu content, having an average radius of about 1 nm to about 5 nm.

[0098] A disclosed alloy can further comprise copper at a the concentration up to about 1% by weight and a dispersion of coherent Al.sub.3Zr and/or Al.sub.3(Sc.sub.xZr.sub.1−x) (0≦x≦1) with Ll.sub.2 crystal structure with an average radius of no more than about 20 nm, such as in the range of 3-20 nm and with an average number density of no less than about 5×10.sup.20/m.sup.3, a dispersion of the incoherent Al.sub.5Mn dispersoids with an average radius in the range of about 50 nm to about 200 nm, a dispersion of Al.sub.12Mn, Al.sub.7Cr (or Al.sub.45Cr.sub.7) intermetallic phases in the range of about 50 nm to about 800 nm in size, a dispersion of coherent Al—Mg—Zn G. P. zones and intermediate phase (precursor of the equilibrium Mg.sub.3Zn.sub.3Al.sub.2, T′ phase) in alloy with low Zn/Mg ratio, having an average radius of about 1 nm to about 5 nm, and a dispersion of coherent Al.sub.2CuMg G. P. zones and intermediate phase, so called θ′ in alloys with Cu content, having an average radius of about 1 nm to about 5 nm.

[0099] Disclosed aluminum alloys may be used to form cast aluminum articles.

[0100] A disclosed method for manufacturing a cast aluminum alloy comprises casting an aluminum alloy comprising [0101] about 3% to about 5% by weight magnesium, [0102] about 0 to about 4.sup.96 by weight zinc, [0103] about 0.6% to about 1% by weight manganese, [0104] about 0.1% to about 0.3% by weight chromium, [0105] about 0.25% to about 0.8% by weight zirconium, and [0106] aluminum as the remainder; and
using a casting method selected from the group of casting methods consisting of squeeze casting, twin-belt casting, twin-roll casting, and strip (bar) casting.

[0107] A disclosed method for manufacturing an aluminum alloy comprises the steps of melting at about 750° C. to about 950° C. (and preferably at about 800° C. to about 950° C.) an alloy mixture comprising: [0108] about 3% to 5% by weight magnesium, [0109] about 0 to about 4% by weight zinc, [0110] about 0.6% to about 1% by weight manganese, [0111] about 0.1% to about 0.3% by weight chromium, [0112] about 0.25% to about 0.8% by weight zirconium, [0113] optionally up to about 0.15% by weight scandium, [0114] optionally up to about 1% by weight copper, [0115] and aluminum as the remainder; with cooling rates of more than about 50° C./s from melt temperature down to about 300° C.; and aging the cast article at a temperature in the range of about 275° C. to about 475° C. for about 2 hours to about 72 hours (preferably in the range of about 350° C. to about 475° C. for about 24 hours to about 72 hours) is disclosed.

[0116] A disclosed method for manufacturing an aluminum alloy can include aging at about 350° C. to about 475° C. for about 2 hours to about 72 hours.

[0117] A disclosed method for manufacturing an aluminum alloy can include a two-step aging process of aging at about 275° C. to about 375° C. for about 2 hours to about 24 hours, followed by aging at about 425° C. to about 475° C. for about 1 hour to about 24 hours.

[0118] A disclosed method for manufacturing an aluminum alloy optionally can include additional lower temperature aging after the higher temperature aging. The additional lower temperature aging comprises aging at about 120° C. to about 200° C. for about 8 hours to about 72 hours.

[0119] A disclosed method for manufacturing an aluminum alloy can be as described above wherein the alloy lacks scandium.

[0120] The present invention has been described in detailed embodiments thereof. It is understood by those skilled in the art that modifications and variations in this detail may be made without departing from the spirit and scope of the claimed invention.

[0121] It is to be understood that no limitation with respect to the specific embodiments illustrated and described is intended or should be inferred.