Ultra-Thick High Strength 7xxx Series Aluminum Alloy Products and Methods of Making Such Products
The present invention is directed to an ultra-thick high strength aluminum alloy, comprising 7.5 to 8.4 wt. % Zn, 1.6 to 2.3 wt. % Mg, 1.4 to 2.1 wt. % Cu, and 0.05 to 0.15 wt. % Zr. This alloy can be fabricated to produce 2-10 inch thick plate, extrusion or forging products, and is especially suitable for aerospace structural components, especially large commercial airplane wing structure applications. The aluminum product has a minimum yield strength of [75 ksi−0.8×(thickness in inch−3.94 inch)] in LT direction and [76 ksi−0.8×(thickness in inch−3.94 inch)] in L direction for more than 2 inch thick product in T7651 temper. Besides strength, product provides necessary damage tolerance performance as well as corrosion resistance performance suitable for aerospace application.
1 . An ultra-thick high strength aluminum alloy product comprising
7.5 to 8.4 wt. % Zn,
1.6 to 2.3 wt. % Mg,
1.4 to 2.1 wt. % Cu, and
one or more elements selected from the group consisting of up to 0.2 wt. % Zr, up to 0.2 wt. % Sc, and up to 0.2 wt. % Hf,
with the balance Al, incidental elements and impurities,
wherein said aluminum alloy product is a 2-10 inches thick plate, extrusion, or forging product and has a minimum yield strength of [75 ksi−0.8×(thickness in inch−3.94 inch)] in LT direction and [76 ksi−0.8×(thickness in inch−3.94 inch)] in L direction.
2 . The ultra-thick high strength aluminum alloy product of claim 1 comprising ≦0.12 wt. % Si.
3 . The ultra-thick high strength aluminum alloy product of claim 2 comprising ≦0.05 wt. % Si.
4 . The ultra-thick high strength aluminum alloy product of claim 1 comprising ≦0.15 wt. % Fe.
5 . The ultra-thick high strength aluminum alloy product of claim 4 comprising ≦0.08 wt. % Fe.
6 . The ultra-thick high strength aluminum alloy product of claim 1 comprising ≦0.04 wt. % Mn.
7 . The ultra-thick high strength aluminum alloy product of claim 1 comprising ≦0.04 wt. % Cr.
8 . The ultra-thick high strength aluminum alloy product of claim 1 comprising ≦0.06 wt. % Ti.
9 . The ultra-thick high strength aluminum alloy product of claim 1 consisting essential of
7.5 to 8.4 wt. % Zn,
1.6 to 2.3 wt. % Mg,
1.4 to 2.1 wt. % Cu, and
one or more elements selected from the group consisting of up to 0.2 wt. % Zr, up to 0.2 wt. % Sc, and up to 0.2 wt. % Hf,
≦0.12 wt. % Si,
≦0.15 wt. % Fe,
≦0.04 wt. % Mn,
≦0.04 wt. % Cr,
and ≦0.06 wt. % Ti
with the balance Al, incidental elements and impurities.
10 . The ultra-thick high strength aluminum alloy product of claim 1 consisting essentially of
7.65-7.95
wt. % Zn
2.00-2.20
wt. % Mg
1.55-1.75
wt. % Cu
0.08-0.11
wt. % Zr
≦0.05
wt. % Si
≦0.08
wt. % Fe
with the balance Al, incidental elements and impurities.
11 . The ultra-thick high strength aluminum alloy product of claim 1 consisting essentially of
7.78-7.94
wt. % Zn
2.06-2.10 wt. % Mg
1.65-1.70 wt. % Cu
0.08-0.09
wt. % Zr
0.03-0.04 wt. % Si
0.06-0.07 wt/% Fe
about 0.03
wt. % Ti
with the balance Al, incidental elements and impurities.
12 . The ultra-thick high strength aluminum alloy product of claim 1 wherein said aluminum alloy product is a 4-10 inches thick plate, extrusion, or forging product.
13 . The ultra-thick high strength aluminum alloy product of claim 12 wherein said aluminum alloy product is a 4-8 inches thick plate, extrusion, or forging product.
14 . The ultra-thick high strength aluminum alloy product of claim 1 wherein said aluminum alloy product is a 2-6 inches thick plate, extrusion, or forging product.
15 . The ultra-thick high strength aluminum alloy product of claim 1 having a minimum short transverse (ST) stress corrosion cracking (SCC) of 25 ksi.
16 . The ultra-thick high strength aluminum alloy product of claim 1 having a minimum short transverse (ST) stress corrosion cracking (SCC) of 30 ksi.
17 . The ultra-thick high strength aluminum alloy product of claim 1 having a minimum short transverse elongation of 2%.
18 . The ultra-thick high strength aluminum alloy product of claim 1 having a minimum short transverse elongation of 3%.
19 . A method of manufacturing an ultra-thick high strength aluminum alloy product of an AA7xxx-series alloy, the method comprising the steps of:
a. casting stock of an ingot of an AA7xxx-series aluminum alloy comprising the aluminum alloy product of claim 1
b. homogenizing the cast stock;
c. hot working the stock by one or more methods selected from the group consisting of rolling, extrusion, and forging;
d. solution heat treating (SHT) of the hot worked stock;
e. cold water quenching said SHT stock;
f. optionally stretching the SHT stock; and
h. ageing of the SHT, cold water quenched and optionally stretched stock to a desired temper.
20 . The method of claim 19 , wherein said step of homogenizing includes homogenizing at temperatures from 454 to 491° C. (850 to 915° F.).
21 . The method of claim 19 , wherein said step of hot working includes hot rolling at a temperature of 399 to 443° C. (750 to 830° F.).
22 . The method of claim 19 , wherein said step of solution heat treating includes solution heat treated at temperature range from 454 to 491° C. (850 to 915° F.).
23 . The method of claim 19 , wherein said step of optionally stretching includes stretching at about 1.5 to 3%.
24 . The method of claim 19 , wherein said step of ageing includes a two-step T7651 ageing process wherein a first stage temperature ranges from 100 to 140° C. (212 to 284° F.) for 4 to 24 hours and a second stage temperature ranges from 150 to 200° C. (212 to 392° F.) for 5 to 20 hours.
25 . The method of claim 19 , wherein
b. said step of homogenizing includes homogenizing at temperatures from 454 to 491° C. (850 to 915° F.);
c. said step of hot working includes hot rolling at a temperature of 399 to 443° C. (750 to 830° F.);
d. said step of solution heat treating includes solution heat treated at temperature range from 454 to 491° C. (850 to 915° F.);
e. said step of cold water quenching includes cold water quenching to room temperature;
f. said step of optionally stretching includes stretching at about 1.5 to 3%;
g. said step of ageing includes a two-step T7651 ageing process wherein a first stage temperature ranges from 100 to 140° C. (212 to 284° F.) for 4 to 24 hours and a second stage temperature ranges from 150 to 200° C. (212 to 392° F.) for 5 to 20 hours.