Aluminum 2055-T84
Precip hard · default condition
AA 2055 · UNS A92055
T84 = 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.
Values for the T84 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 |
|---|---|---|---|---|---|---|
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 |
T84DefaultThis page 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-T84?
2055-T84 is 2055 in the T84 condition — standard commercial condition for 2055 extrusions and plate: maximum strength for lower-wing stringers and fuselage longerons. 2055-T84 has a yield strength of 600 MPa (87 ksi) and a tensile strength of 640 MPa (92.8 ksi) — stronger than 98% of aluminum grades. Elongation at break is 10% and the elastic modulus is 78 GPa (11.3 Msi). 2055-T84 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).
Advantages
- High strength — 600 MPa (87 ksi), better than 98% of aluminum grades
- Tough — resists crack growth — 33 MPa·√m (30 ksi·√in), better than 87% of aluminum grades
Limitations
- Poor heat conductor — 95 W/m·K (54.9 BTU/hr·ft·°F), worse than 98% of aluminum grades
- Low electrical conductivity — 27 % IACS, worse than 86% of aluminum grades
- Difficult to weld — 22/100, worse than 83% of aluminum grades
- Needs corrosion protection — 40/100, worse than 75% of aluminum grades
2055-T84 properties
Typical room-temperature values for 2055-T84; 14 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-T84 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-T84 has a yield strength of 600 MPa (87 ksi) and a tensile strength of 640 MPa (92.8 ksi) — stronger than 98% of aluminum grades. Elongation at break is 10% and the elastic modulus is 78 GPa (11.3 Msi).
Thermal6
2055-T84 is rated for continuous service to 150°C (302 °F). It conducts heat at 95 W/m·K (54.9 BTU/hr·ft·°F), worse than 98% of aluminum grades. Thermal expansion is 22.6 µm/m·K (12.6 µin/in·°F).
Electrical3
2055-T84 conducts electricity at 27 % IACS, worse than 86% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (40/100), worse than 75% of aluminum grades.
Sustainability4
Producing a kilogram of 2055-T84 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-T84's machinability is very good (70/100, better than 72% of aluminum grades); weldability poor (22/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 2055-T84
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-T84 — frequently asked
What is 2055-T84 used for?
2055-T84 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-T84?
2055-T84 has a typical yield strength of 600 MPa (87 ksi) and a tensile strength of 640 MPa (92.8 ksi) — stronger than 98% of aluminum grades. Strength varies by condition: see the 6 listed tempers.
Is 2055-T84 easy to machine?
Yes — machinability is rated very good (70/100, better 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-T84 be welded?
Not readily — weldability is rated poor (22/100). 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-T84?
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-T84 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-T84?
2055-T84 is rated for continuous use to about 150°C (302 °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.