Aluminum 2055-O (Annealed)
Temper
AA 2055 · UNS A92055
Rarely stocked; used for severe forming or for re-solution-treating scrap/blanks before final T8x aging.
Values for the O condition
Other 2055 tempers and conditions
2055 is listed in 6 conditions; see the grade overview at 2055.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
OThis page Annealed | Rarely stocked; used for severe forming or for re-solution-treating scrap/blanks before final T8x aging. | 150 | 270 | 20 | 80 HB | 33 % IACS |
Solution heat treated, cold worked and naturally aged | Interim mill/shop condition supplied when the fabricator wants to stretch, form or straighten parts before final artificial aging. | 320 | 460 | 15 | 130 HB | 24 % IACS |
T8, stress relieved by stretching | Plate condition for machined ribs, spar and floor-beam parts where residual-stress control and dimensional stability after machining matter. | 550 | 595 | 9 | 170 HB | 28 % IACS |
Solution treated, cold worked and artificially aged | Choose when damage tolerance and fracture toughness are weighted above the last few percent of strength. | 565 | 615 | 11 | 172 HB | 26 % IACS |
T84 process with stress relief by stretching plus minor straightening | Pick for long extruded stringers/profiles where tight straightness and low residual stress are required after peak aging. | 595 | 635 | 10 | 178 HB | 27 % IACS |
T84Default Solution heat treated, cold worked (stretched) and artificially aged to… | Standard commercial condition for 2055 extrusions and plate: maximum strength for lower-wing stringers and fuselage longerons. | 600 | 640 | 10 | 180 HB | 27 % IACS |
What is 2055-O?
2055-O is 2055 in the O temper — rarely stocked; used for severe forming or for re-solution-treating scrap/blanks before final T8x aging. 2055-O has a yield strength of 150 MPa (21.8 ksi) and a tensile strength of 270 MPa (39.2 ksi) — weaker than 65% of aluminum grades. Elongation at break is 20% and the elastic modulus is 76 GPa (11 Msi). 2055-O has a density of 2.74 g/cm³ (0.099 lb/in³), heavier than 64% of aluminum grades. It melts at 545°C (1,013 °F). T84 is the default condition FabDigit quotes; O is available on request or by drawing note.
Advantages
- High service temperature — 200°C (392 °F), better than 90% of aluminum grades
- Ductile — tolerates forming and impact — 20%, better than 89% of aluminum grades
- Tough — resists crack growth — 33 MPa·√m (30 ksi·√in), better than 87% of aluminum grades
- Forms and bends easily — 70/100, better than 83% of aluminum grades
Limitations
- Poor heat conductor — 115 W/m·K (66.4 BTU/hr·ft·°F), worse than 85% of aluminum grades
2055-O properties
Typical room-temperature values for 2055-O; 20 are specific to this condition. Other listed values are 2055 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
2055-O has a density of 2.74 g/cm³ (0.099 lb/in³), heavier than 64% of aluminum grades. It melts at 545°C (1,013 °F).
Mechanical12
2055-O has a yield strength of 150 MPa (21.8 ksi) and a tensile strength of 270 MPa (39.2 ksi) — weaker than 65% of aluminum grades. Elongation at break is 20% and the elastic modulus is 76 GPa (11 Msi).
Thermal6
2055-O is rated for continuous service to 200°C (392 °F). It conducts heat at 115 W/m·K (66.4 BTU/hr·ft·°F), worse than 85% of aluminum grades. Thermal expansion is 22.6 µm/m·K (12.6 µin/in·°F).
Electrical3
2055-O conducts electricity at 33 % IACS, worse than 57% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (48/100), worse than 58% of aluminum grades.
Sustainability4
Producing a kilogram of 2055-O takes about 215 MJ of energy and emits 13 kg of CO₂ — more than 93% of aluminum grades. Typical recycled content is 5%.
Manufacturability6
2055-O's machinability is fair (45/100, worse than 72% of aluminum grades); weldability poor (30/100); formability very good (70/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 2055-O
Is 2055 easy to machine?
Machines well in T8x with sharp carbide/PCD tooling, high speed and generous flood coolant; expect springback-free chips but budget for stress-relieved (T851/T8511) stock to avoid distortion in thin machined webs.
Can 2055 be welded?
Not suitable for arc fusion welding (hot cracking, Li-oxide porosity); join by riveting/bolting or by friction stir welding with post-weld surface protection.
Can 2055 be formed, bent or molded?
Form, stretch or bend in the O or T3 interim condition and then artificially age to T84; T8x tempers have limited cold ductility and require generous bend radii.
What surface finishes work on 2055?
Alkaline clean + deoxidize, then chromic/thin-film sulfuric or tartaric-sulfuric anodize plus chromate-free primer; Li at the surface hydrates readily, so avoid strongly alkaline baths and seal promptly.
2055 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Si | ≤ 0.06 | — |
| Fe | ≤ 0.1 | — |
| Cu | 3.2 – 4 | 3.6 |
| Mn | 0.1 – 0.5 | 0.3 |
| Mg | 0.2 – 0.6 | 0.4 |
| Zn | 0.3 – 0.7 | 0.5 |
| Zrgrain-structure control | 0.05 – 0.15 | 0.1 |
| Lidensity reduction / modulus increase | 1 – 1.3 | 1.15 |
| Agaids T1 precipitation | 0.2 – 0.7 | 0.4 |
| Ti | ≤ 0.1 | — |
| Others (each)each | ≤ 0.05 | — |
| Others (total)total | ≤ 0.15 | — |
| Al | balance | — |
2055-O — frequently asked
What is 2055-O used for?
2055-O is typically used for lower wing skins, fuselage frames, machined stringers and extruded stiffeners, wing spar caps, highly loaded fittings and lugs and floor beams and seat tracks. In short: strongest Al-Cu-Li plate; 600 MPa aerospace grade; machined structure only.
What is the yield strength of 2055-O?
2055-O has a typical yield strength of 150 MPa (21.8 ksi) and a tensile strength of 270 MPa (39.2 ksi) — weaker than 65% of aluminum grades. Strength varies by condition: see the 6 listed tempers.
Is 2055-O easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 72% of aluminum grades). Machines well in T8x with sharp carbide/PCD tooling, high speed and generous flood coolant; expect springback-free chips but budget for stress-relieved (T851/T8511) stock to avoid distortion in thin machined webs.
Can 2055-O be welded?
Not readily — weldability is rated poor (30/100). Not suitable for arc fusion welding (hot cracking, Li-oxide porosity); join by riveting/bolting or by friction stir welding with post-weld surface protection.
What surface finishes work on 2055-O?
Alkaline clean + deoxidize, then chromic/thin-film sulfuric or tartaric-sulfuric anodize plus chromate-free primer; Li at the surface hydrates readily, so avoid strongly alkaline baths and seal promptly.
Can 2055-O be formed, bent or molded?
Form, stretch or bend in the O or T3 interim condition and then artificially age to T84; T8x tempers have limited cold ductility and require generous bend radii.
What is the maximum service temperature of 2055-O?
2055-O is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 2055-T84 and 2055-O?
T84 is the default condition — standard commercial condition for 2055 extrusions and plate: maximum strength for lower-wing stringers and fuselage longerons. O: rarely stocked; used for severe forming or for re-solution-treating scrap/blanks before final T8x aging. Yield strength is 600 MPa in T84 versus 150 MPa in O.
Sources
- Registration Record of International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets) — The Aluminum Association (2018)
- 2055-T84 Al-Li extrusion / plate product information — Alcoa / Arconic (2015)
- ASM Handbook Vol. 2: Properties and Selection — Nonferrous Alloys — ASM International (1990)
- Aluminum-Lithium Alloys: Processing, Properties and Applications — Elsevier/Butterworth-Heinemann (2014)
- MMPDS-style typical mechanical property compilations for Al-Cu-Li alloys — Battelle/FAA (2021)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.