Specifications

ALUMINUM ALLOY 7255-T7751
Very High Strength, Fatigue-Resistant Plate
DESCRIPTION
APPLICATIONS
Alcoa developed aluminum alloy AA 7255 plate for use in
aerospace applications requiring very high strength and
fatigue resistance. Compared to alloy 7075, 7150 and 7055
plate, alloy 7255 offers higher strength and improved fatigue
resistance with similar or better fracture toughness and
corrosion resistance.
Alloy 7255 plate can replace alloys 7075, 7150 and 7055
and other high strength plate alloys in applications requiring
high tensile or compressive strength such as upper wing
panels. The machining and fabrication characteristics of
7255 plate are the same or very similar to that of other high
strength 7xxx plate products.
Alloy 7255 plate is available in the plant-aged T7751 temper
and in the W51 temper for user age forming to the T79E01*
temper. The available thickness range for 7255 plate is 0.75
to 1.5 inches (19.0 to 38.1 mm).
*Alcoa’s internal designation for age formable temper.
COMMERCIAL STATUS
Alcoa alloy 7255 plate has been supplied commercially to
customer and industry specifications since 2003 and is
currently used for upper wing panels on commercial aircraft.
7255-T7751 is covered by AMS 4463 and material design
allowables are available in the MMPDS Handbook.
CHEMICAL COMPOSITION AND MECHANICAL PROPERTIES
The following tables and figures show the composition of 7255, and how the plant-aged T7751 and the T79E01 age
form temper compare with each other and 7075, 7150 and 7055.
Chemical Composition Limits • AA 7255 (Wt.%)*
Zn
Cu
Mg
Zr
Mn
Cr
Ti
Si
Fe
Al
7.6 – 8.4
2.0 – 2.6
1.8 – 2.3
0.08 – 0.15
0.05 max
0.04 max
0.06 max
0.06 max
0.09 max
Remainder
*Other elements: 0.05 wt.% max (each); 0.15 wt.% max (total)
Static Properties • 7255 Plate • Minimum Values (S or A-Basis)
Alloy/Temper
Dir.
Thickness, Inch (mm)
7255-T7751
(AMS 4463)
7255-T79E01
(S or A est.*)
7075-T651
(AMS 4045)
7150-T7751
(AMS 4252)
7055-T7751
(AMS 4206)
0.75 – 1.50
(19.0 – 38.1)
0.50 – 1.00
(12.7 – 38.1)
1.00 – 2.00
(25.4 – 50.8)
0.75 – 1.50
(19.0 – 38.1)
0.50 – 1.50
(12.7 – 38.1)
Tensile Strength,
Ftu, ksi (MPa)
L
91 (627)
88 (607)
76 (524)
84 (579)
89 (614)
LT
91 (627)
88 (607)
77 (531)
84 (579)
89 (614)
Tensile Yield, Fty,
ksi (MPa)
L
88 (607)
86 (593)
69 (476)
78 (538)
86 (593)
LT
86 (593)
84 (579)
67 (462)
77 (531)
85 (586)
L
9
8
na
8
7
LT
7
7
6
8
8
L
88 (607)
86 (593)
66 (455)
77 (531)
86 (593)
Elongation, %, 4D
Comp. Yield, Fcy ksi
(MPa)
*T79E01 is Alcoa’s internal designation for the age formable temper. Properties obtained from lot release capability tests to demonstrate
aging response of W51 temper. Estimated minimum values determined in accordance with MMPDS guidelines, but have not been
approved by AMS or MMPDS. User minimums may differ depending on time and temperature capability of age forming equipment.
CONTACT AND PROCUREMENT
For additional information on 7255 plate, contact your local Alcoa Sales Account Manager.
FATIGUE AND DAMAGE TOLERANCE PROPERTIES
The fracture toughness and fatigue crack growth resistance of 7255
is similar to 7075, 7150, and 7055. The S-N fatigue resistance of
7255 is improved over these same alloys. The level of improvement
will depend on stress concentration factor, (Kt), and specimen and
testing details.
FCG Curves
1.0E-03
1.0E-04
Fracture Toughness • 7255-T7751
7255-T7751
7055-T7751
7150-T7751
7075-T651
Orient.
KIc Minimum
ksi√in (MPa√m)
KIc Typical
ksi√in (MPa√m)
L-T
22 (24)
24 (26)
T-L
21 (23)
24 (26)
L-T
22 (24)
24 (26)
T-L
21 (23)
24 (26)
L-T
22 (24)
na
7055-T7751
T-L
20 (22)
na
7255-T7751
L-T
na
26 (29)
T-L
na
22 (24)
da/dN (in/cycle)
Alloy/Temper
L-T Orientation
R=0.1, RH>90%
Frequency=25 Hz
1.0E-05
7150-T7751
1.0E-06
1.0E-07
1
10
100
K (ksi in)
S-N Fatigue, Kt = 2.5
S-N Fatigue, Kt = 2.3
35
7055-T79E01
7255-T79E01
25
20
L Direction
Open Hole, Kt=2.3 (net)
R=0.1, RH>90%
Frequency=25 Hz
15
1.0E+04
1.0E+05
1.0E+06
1.0E+07
1.0E+08
Maximum Net Stress (ksi)
Maximum Net Stress (ksi)
30
L, Direction, Open Hole
Kt=2.5 (net)
R=0.1, Lab Air
Frequency: 25-30 Hz
30
25
7055-T7751
7255-T7751
20
1.0E+04
Fatigue Life (Cycles)
1.0E+05
1.0E+06
1.0E+07
Cycles to Failure
CORROSION RESISTANCE
The exfoliation corrosion and SCC resistance of 7255 in the T7751 and T79E01 tempers is the same as 7055 in the same
temper, and superior to 7xxx alloys in T6 tempers. The minimum guaranteed EXCO (ASTM G34) is EB for the T7751 temper
and EC for the T79E01 temper. The minimum guaranteed SCC resistance (ASTM G47) of the T79E01 temper in the ST
direction is 16 ksi (110 MPa) compared to a typical SCC resistance of < 10 ksi (69 MPa) for 7075 in the T6 temper.
ALCOA AEROSPACE AND AUTOMOTIVE PRODUCTS
P.O. BOX 8025 • BETTENDORF, IOWA 52722 • 1-800-523-9596 • www.alcoa.com
Product specifications are subject to change without notice.
©2016 Alcoa Inc.
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