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