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Aluminum Alloy 2055-T84 Extrusions
High Strength, Fatigue Resistant, Low Density Extrusions
DESCRIPTION
APPLICATIONS
Alcoa has developed Al-Li alloy AA 2055 extrusions for use
in aerospace and other applications requiring high tensile or
compressive strength, high modulus, high fatigue resistance
and low density with good fracture toughness and corrosion
resistance. Li additions increase the strength and modulus of
Al-Li alloys while lowering their density. The density of 2055 is
4 to 5% less than high strength 7xxx alloys.
The combination of high strength, stiffness, damage
tolerance and durability makes 2055 suitable as a replacement for high strength 7xxx and 2xxx alloys in applications
such as fuselage stringers and floor beams, and other
statically and dynamically-loaded applications requiring
high strength and stiffness.
COMMERCIAL STATUS
Alloy 2055 extrusions are available in the T84 temper from
0.040 to 1.500 inches (1.02 to 38.1 mm) thick. 2055-T84
extrusions exhibit very good machining, finishing and forming
characteristics.
Alcoa alloy 2055-T84 extrusions are covered by AMS 4257.
Material design allowables including static properties,
physical properties, fracture toughness, corrosion resistance
and S-N fatigue are available in MMPDS.
CHEMICAL COMPOSITION Chemical Composition Limits • AA 2055 (Wt.%)*
Cu
Li
Zn
Ag
Mg
Mn
Zr
Fe
Si
Al
3.2-4.2
1.0-1.3
0.30-0.7
0.20-0.7
0.20-0.6
0.10- 0.50
0.05-0.15
0.10 max
0.07 max
Remainder
* Other elements: 0.05 wt.% max (each); 0.15 wt.% max (total); Ti 0.10 max
TOUGHNESS AND FATIGUE
The damage tolerance and durability properties of 2055-T84 extrusions are superior to high strength 7xxx extrusions
providing an improved combination of strength and toughness, superior FCG resistance and better S-N fatigue resistance.
Toughness vs. Strength
30
7055-T76511
7075-T6511
7150-T77511
25
20
Maximum Net Stress (ksi)
2055-T84
7055-T77511
50
B=0.25 in.
da/dN (in/cycle)
L-T toughness, KIc, typical, (ksi in)
M(T) Specimen, W=4 in.
RH>90%, Freq.=25 HZ
7055-T74511
35
S-N Fatigue
FCG Curves, L-T Orientation
40
40
35
30
25
75
80
85
90
95
Longitudinal yield strength, minimum (ksi)
K (ksi in)
Did not fail
20
15
70
L Direction, Open Hole
Kt =2.5 (net)
R=0.1, Humid Air
Frequency: 25-30 Hz
45
10
1.0E+04
7055-T7E127*, 0.34-1.60 in. (5 lots)
2055-T84, 0.20-1.50 in. (9 lots)
1.0E+05
* T7E127 is Alcoa’s internal designation for an age formable temper
CONTACT AND PROCUREMENT
For additional information on 2055-T84 extrusions, contact your local Alcoa Sales Account Manager.
1.0E+06
Cycles to Failure
1.0E+07
1.0E+08
MECHANICAL PROPERTIES
The strength of 2055-T84 extrusions is similar to that of AA 7150 extrusions and superior to that of older 7xxx alloys such as
7075 and 7050, while providing higher stiffness, similar or better fracture toughness and lower density.
Static Properties • 2055-T84 Extrusions • MMPDS Minimum Values (A- or S-Basis)
Dir.
Property
Ult. Tensile,
Ftu (A),
ksi (MPa)
Yield Strength,
Fty (A),
ksi (MPa)
2055-T84 Extrusions (AMS 4257)
Thickness
(in.)
0.040-0.125
0.126-0.249
0.250-0.499
0.500-0.749
0.750-1.249
1.250-1.500
mm
1.02 - 3.18
3.20 - 6.32
6.35 - 12.67
12.70 - 19.02
19.05 - 31.72
31.75 - 38.10
L
82 (565)
83 (572)
85 (586)
87 (600)
88 (607)
90 (620)
LT
--
84 (579)
84 (579)
84 (579)
84 (579)
84 (579)
L
78 (538)
79 (545)
80 (552)
82 (565)
84 (579)
86 (593)
LT
--
78 (538)
78 (538)
78 (538)
78 (538)
78 (538)
L
5
6
7
8
8
8
LT
--
5
5
5
5
5
L
80 (552)
81 (558)
81 (558)
83 (572)
84 (579)
87 (600)
LT
--
--
84 (579)
84 (579)
84 (579)
84 (579)
L
--
--
--
--
22 (24)
22 (24)
LT
--
--
--
--
19 (21)
19 (21)
% El. (S) (4D)
Compression
Yield Strength,
Fcy (A), ksi (MPa)
Fracture Toughness, KIc,ksi√in
(MPa√m)
Tension /
Compression
Modulus, Msi
(GPa)
11.1 (76.5) / 11.5 (79.3)
Density, lbs / in3
(g/cm3)
0.098 (2.71)
CORROSION RESISTANCE
The exfoliation corrosion and SCC resistance of 2055-T84 extrusions is similar or better than that of 7xxx alloys in the
T76 and T77 tempers and superior to the T6 tempers. The typical exfoliation rating of 2055-T84 extrusions is P (pitting,
no exfoliation). The minimum guaranteed SCC resistance (ASTM G47) in the ST direction is 25 ksi (172 MPa). The good
corrosion resistance of 2055-T84 extrusions has been demonstrated in both accelerated and seacoast environments.
ALCOA FORGINGS AND EXTRUSIONS
3131 MAIN STREET • LAFAYETTE, INDIANA 47905 • (765) 771-3521 • www.alcoa.com
Product specifications are subject to change without notice.
©2016 Alcoa Inc. 2/16