US2020232072A1PendingUtilityA1
Al-zn-cu-mg alloys with high strength and method of fabrication
Est. expirySep 26, 2037(~11.2 yrs left)· nominal 20-yr term from priority
C22F 1/053C22C 21/10B64C 3/185B64C 3/187
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Claims
Abstract
The invention relates to a rolled product made of aluminum alloy with a thickness of at least 50 mm comprising (in weight %): Zn 6.9-7.5; Mg 1.8-2.2; Cu 1.8-2.2, where the sum Cu+Mg is between 3.8 and 4.2; Zr 0.04-0.14; Mn 0-0.1; Ti 0-0.15; V 0-0.1; Fe≤0.15; If≤0.15; impurities ≤0.05 each and ≤0.15 total, balance aluminum. The invention also relates to the method of manufacturing such a product. The products according to the invention are particularly advantageous because they have a very favorable compromise between static mechanical strength, toughness and environmental-assisted cracking performance under conditions of high stress and humid environment.
Claims
exact text as granted — not AI-modified1 . A rolled aluminum-based alloy product having a thickness of at least 50 mm comprising, in weight %:
Zn 6.9-7.5 Mg 1.8-2.2 Cu 1.8-2.2, wherein the sum Cu+Mg is between 3.8 and 4.2 Zr 0.04-0.14 Mn 0-0.1 Ti 0-0.15 V 0-0.1 Fe≤0.15 Si≤0.15 impurities ≤0.05 each and ≤0.15 wt. % total, balance aluminum.
2 . A product according to claim 1 wherein Cu 1.90-2.15.
3 . A product according to claim 1 , wherein Mg 1.90-2.10.
4 . A product according to claim 1 , wherein Zn 7.0-7.20.
5 . A product according to claim 1 , wherein Cu>2.7*Mg−0.5*Zn and optionally Cu>2.7*Mg−0.5*Zn+0.1.
6 . A product according to claim 1 wherein Cu is less than 2.7*Mg−0.5*Zn+0.3, optionally less than 2.7*Mg−0.5*Zn+0.25 and optionally less than 2.7*Mg−0.5*Zn+0.2.
7 . A product according to claim 1 , wherein said product has the following properties:
a) a minimum life without failure after Environmentally Assisted Cracking under conditions of high stress, at a short transverse stress level of 85% of the product tensile yield strength in ST direction, and humid environment with 85% relative humidity at a temperature of 70° C., of at least 40 days, b) a conventional tensile yield strength measured in the ST direction at mid thickness of at least 467−0.27*t MPa and optionally of 477−0.27*t MPa and optionally of 487−0.27*t MPa, t being the thickness of the product in mm, c) a K 1C toughness in the S-L direction measured at mid thickness of at least 26−0.01*t MPa√m and optionally 28−0.01*t MPa√m and optionally 30−0.01*t MPa√m, t being the thickness of the product in mm.
8 . A product according to claim 7 wherein the product has the following properties
d) a conventional tensile yield strength measured in the L direction at quarter thickness of at least 505−0.26*t MPa and optionally of 515−0.26*t MPa and optionally of 525−0.26*t MPa, t being the thickness of the product in mm,
e) a K 1C toughness in the L-T direction measured at quarter thickness of at least 36−0.1*t MPa√m and optionally 37−0.1*t MPa√m and optionally 38−0.1*t MPa√m, t being the thickness of the product in mm.
9 . A product according to claim 1 wherein the thickness thereof is from 50 to 150 mm.
10 . A product according to claim 1 where the Cu content is from 1.95 to 2.15 wt. % and wherein the product has the following properties:
a) a minimum life without failure after Environmentally Assisted Cracking under conditions of high stress, at a short transverse stress level of 85% of the product tensile yield strength in ST direction, and humid environment with 85% relative humidity at a temperature of 70° C., of at least 40 days, optionally 80 days and optionally 120 days,
b) a conventional tensile yield strength measured in the ST direction at mid thickness of at least 477−0.27*t MPa and optionally of 487−0.27*t MPa and optionally of 497−0.27*t MPa, t being the thickness of the product in mm,
c) a K 1C toughness in the S-L direction measured at mid thickness of at least 28−0.01*t MPa√m and optionally 30−0.01*t MPa√m and optionally 032−0.01*t MPa√m, t being the thickness of the product in mm.
11 . A product according to claim 10 wherein the product has the following properties:
d) a conventional tensile yield strength measured in the L direction at quarter thickness of at least 515−0.26*t MPa and optionally of 525−0.26*t MPa and optionally of 535−0.26*t MPa (t being the thickness of the product in mm),
e) a K 1C toughness in the L-T direction measured at quarter thickness of at least 42−0.1*t MPa√m and optionally 43-0.1*t MPa√m and optionally 44−0.1*t MPa√m (t being the thickness of the product in mm).
12 . A structural member suitable for the construction of aircraft comprising a product according to claim 1 .
13 . A structural member according to claim 12 wherein said structural member is used in wing ribs, spars and frames.
14 . A process for manufacture of a rolled aluminum-based alloy product comprising:
a) casting an ingot comprising, or consisting essentially of (in weight-%)
Zn 6.9-7.5
Mg 1.8-2.2
Cu 1.8-2.2, wherein the sum Cu+Mg is between 3.8 and 4.2
Zr 0.04-0.14
Mn 0-0.1
Ti 0-0.15
V 0-0.1
Fe 0.15
Si 0.15
impurities ≤0.05 each and ≤0.15 wt. % total, balance aluminum. b) homogenizing the ingot c) hot rolling said homogenized ingot to a rolled product with a final thickness of at least 50 mm; d) solution heat treating and quenching the product; e) stretching the product; f) artificial aging with the equivalent aging time t(eq) at 155° C. is comprised between 24 and 70 hours and optionally between 28 and 40 hours, equivalent time t(eq) at 155° C. being defined by the formula:
t
(
eq
)
=
∫
exp
(
-
1
6
0
0
0
/
T
)
d
t
exp
(
-
1
6
0
0
0
/
T
ref
)
where T is the instantaneous temperature in ° K during annealing and T ref is a reference temperature selected at 155° C. (428° K), t(eq) is expressed in hours.Cited by (0)
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