High-strength aluminum alloy and process for producing same

Patent metadata

Field	Value
Publication number	US-9512510-B2
Application number	US-201214349239-A
Country	US
Kind code	B2
Filing date	Nov 5, 2012
Priority date	Nov 7, 2011
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

A high-strength aluminum alloy material having a chemical composition which includes Zn: more than 7.2% (mass %, the same applies hereafter) and 8.7% or less, Mg: 1.3% or more and 2.1% or less, Cu: 0.01% or more and 0.10% or less, Zr: 0.01% or more and 0.10% or less, Cr: less than 0.02%, Fe: 0.30% or less, Si: 0.30% or less, Mn: less than 0.05%, Ti: 0.001% or more and 0.05% or less, the balance being Al and unavoidable impurities, is provided. It has a proof stress of 350 MPa or more, and a metallographic structure formed of a recrystallized structure, and L* and b* values, as defined in JIS Z8729 (ISO 7724-1), are 85 or more and 95 or less and 0 or more and 0.8 or less, respectively, as measured after anodization using a sulfuric acid bath.

First claim

The invention claimed is:

1. An aluminum alloy material, comprising in mass percent:
Zn: more than 7.2% and 8.7% or less,
Mg: 1.3% or more and 2.1% or less,
Cu: 0.01% or more and 0.10% or less,
Zr: 0.01% or more and 0.10% or less,
Cr: less than 0.02%,
Fe: 0.30% or less,
Si: 0.30% or less,
Mn: less than 0.05%,
Ti: 0.001% or more and 0.05% or less,
the balance being Al and unavoidable impurities;
wherein the aluminum alloy material has a proof stress of 350 MPa or more, and a metallographic structure consisting essentially of a recrystallized structure, and
the aluminum alloy material has a composition and microstructure capable of achieving an L* value, as defined in ISO 7724-1, of 85-95 and a b* value, as defined in ISO 7724-1, of 0-0.8, as measured after anodization of the aluminum alloy material in a sulfuric acid bath.

2. The aluminum alloy material according to claim 1 , wherein:
the recrystallized structure includes crystal grains having an average particle diameter of 500 μm or less, and
a crystal grain length in a direction parallel to a hot working direction is 0.5 to 4 times as long as a crystal grain length in a direction perpendicular to the hot working direction.

3. The aluminum alloy material according to claim 2 , wherein Zn is more than 7.5% and 8.5% or less.

4. The aluminum alloy material according to claim 3 , wherein the crystal grains have an average particle diameter of 50 μm or more.

5. The aluminum alloy material according to claim 4 , wherein the recrystallized structure is a granular recrystallized structure.

6. The aluminum alloy material according to claim 1 , wherein Zn is more than 7.5% and 8.5% or less.

7. The aluminum alloy material according to claim 2 , wherein the crystal grains have an average particle diameter of 50 μm or more.

8. The aluminum alloy material according to claim 1 , wherein the recrystallized structure is a granular recrystallized structure.

9. A process for producing the aluminum alloy material according to claim 1 , which comprises:
preparing an ingot having a chemical composition which comprises in mass percent Zn: more than 7.2% and 8.7% or less, Mg: 1.3% or more and 2.1% or less, Cu: 0.01% or more and 0.10% or less, Zr: 0.01% or more and 0.10% or less, Cr: less than 0.02%, Fe: 0.30% or less, Si: 0.30% or less, Mn: less than 0.05%, Ti: 0.001% or more and 0.05% or less, the balance being Al and unavoidable impurities;
performing a homogenization treatment that heats the ingot at a temperature of higher than 540° C. and 580° C. or lower for 1 hour to 24 hours;
subsequently, forming a wrought material by performing hot working on the ingot in a state where the temperature of the ingot at the beginning of the working is 440° C. to 560° C.;
while the wrought material is still at 400° C. or higher, starting to cool it and subsequently performing a quenching treatment such that, while the wrought material is cooling down from 400° C. to 150° C., the average cooling rate is 5° C./sec. or more and 1000° C./sec. or less;
cooling the temperature of the wrought material to room temperature by said quenching treatment or by an additional cooling treatment; and
thereafter, performing a first artificial aging treatment that heats the wrought material at a temperature of 80° C. to 120° C. for 1 hour to 5 hours, and continuously after the first artificial aging treatment, performing a second artificial aging treatment that heats the wrought material at a temperature of 130° C. to 200° C. for 2 hours to 15 hours,
wherein the wrought material has a proof stress of 350 MPa or more, and a metallographic structure consisting essentially of a recrystallized structure, and
the wrought material has a composition and microstructure capable of achieving an L* value, as defined in ISO 7724-1, of 85-95 and a b* value, as defined in ISO 7724-1, of 0-0.8, as measured after anodization of the aluminum alloy material in a sulfuric acid bath.

10. The process according to claim 9 , wherein the average cooling rate during the quenching treatment is 100° C./sec. or more.

11. The process according to claim 10 , wherein the hot working involves extrusion or rolling.

12. The process according to claim 11 , wherein the second artificial aging treatment is performed at a temperature of 170° C. to 200° C.

13. The process according to claim 12 , further comprising anodizing the wrought material after the artificial aging treatment.

14. The process according to claim 9 , wherein:
the homogenization treatment is performed at 560° C. for 12 hours,
the hot working comprises subjecting the ingot to hot-rolling and is initiated while the temperature of the ingot is at 450° C.,
the quenching treatment is initiated while the temperature of the wrought material is at 404° C. and the average cooling rate of the quenching treatment is 950° C./sec,
the first artificial aging treatment involves heating the wrought material at 90° C. for 3 hours, and
the second artificial aging treatment involves heating the wrought material at 150° C. for 8 hours.

15. The process according to claim 14 , further comprising anodizing the wrought material after the artificial aging treatment.

16. The process according to claim 9 , wherein the hot working involves extrusion or rolling.

17. The process according to claim 9 , further comprising anodizing the wrought material after the artificial aging treatment.

18. The process according to claim 9 , wherein the second artificial aging treatment is performed at a temperature of 170° C. to 200° C.

19. A process for producing the aluminum alloy material of claim 1 , comprising:
homogenizing an ingot having the elemental composition recited in claim 1 at a temperature of higher than 540° C. and 580° C. or lower for at least 1 hour;
hot working the homogenized ingot, the hot working being initiated while the temperature of the homogenized ingot it 440° C. to 560° C.;
quenching hot worked material to 150° C. or lower, the quenching being initiated while the hot worked material is at a temperature of 400° C. or higher and is performed such that, while the wrought material is cooling down from 400° C. to 150° C., the average cooling rate is 5° C./sec. or more and 1000° C./sec. or less,
cooling the hot worked material to room temperature; and
subjecting the cooled material to a first artificial aging treatment at a temperature of 80° C. to 120° C. for 1 hour to 5 hours, and continuously thereafter, to a second artificial aging treatment at a temperature of 130° C. to 200° C. for 2 hours to 15 hours,
wherein the aluminum alloy material has a proof stress of 350 MPa or more, and a metallographic structure consisting essentially of a recrystallized structure, and
the aluminum alloy material has a composition and microstructure capable of achieving an L* value, as defined in ISO 7724-1, of 85-95 and a b* value, as defined in ISO 7724-1, of 0-0.8, as measured after anodization of the aluminum alloy material in a sulfuric acid bath.

20. A process for producing the aluminum alloy material according to claim 1 , which comprises:
preparing an ingot having a chemical composition which comprises in mass percent Zn: more than 7.2% and 8.7% or less, Mg: 1.3% or more and 2.1% or less, Cu: 0.01% or more and 0.10% or less, Zr: 0.01% or more and 0.10% or less, Cr: less than 0.02%, Fe: 0.30% or less, Si: 0.30% or less, Mn: less than 0.05%, Ti: 0.001% or more and 0.05% or less, the balance being Al and unavoidable impurities;
performing a homogenization treatment that

Assignees

• Uacj Corp

Inventors

• HATTA Hidenori

Classifications

• C22C21/10

  with zinc as the next major constituent · CPC title

• C22F1/00

  Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working (apparatus for mechanical working of metal B21, B23, B24) · CPC title

• C22C21/00

  Alloys based on aluminium · CPC title

• C22F1/053 Primary

  of alloys with zinc as the next major constituent · CPC title