Aluminum 2099-T81
Temper
AA 2099 · UNS A92099
T81 = solution heat treated, slightly cold worked, artificially aged
Used where 2099 is supplied as plate/flat product for machined ribs and panels; lower strength, better toughness than T83/T86.
Values for the T81 condition
Other 2099 tempers and conditions
2099 is listed in 6 conditions; see the grade overview at 2099.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest condition, used only as an intermediate mill/processing state for severe forming; not a service temper. | 145 | 270 | 18 | 75 HB | 34 % IACS |
Solution heat treated, cold worked and naturally aged | Interim condition supplied for stretch-forming/bending of profiles before final T8-type aging. | 265 | 400 | 15 | 110 HB | 25 % IACS |
T81This page Solution heat treated, slightly cold worked, artificially aged | Used where 2099 is supplied as plate/flat product for machined ribs and panels; lower strength, better toughness than T83/T86. | 480 | 530 | 8 | 142 HB | 31 % IACS |
Proprietary T8-type age for thick/heavy extrusions and forgings | Choose for thick-section extrusions and forgings needing balanced strength with higher through-thickness toughness and SCC resistance. | 495 | 545 | 9 | 145 HB | 31 % IACS |
T83Default Solution heat treated, stress-relieved by stretching, artificially aged | Standard high-strength aerospace extrusion temper — pick for stringers, floor beams and rib/spar profiles. | 520 | 560 | 8 | 150 HB | 30 % IACS |
Solution heat treated, cold worked/stretched more heavily, artificially… | Highest-strength condition for thin extruded stringers where stiffness/strength dominates over toughness. | 560 | 595 | 6 | 158 HB | 30 % IACS |
What is 2099-T81?
2099-T81 is 2099 in the T81 temper — used where 2099 is supplied as plate/flat product for machined ribs and panels; lower strength, better toughness than T83/T86. 2099-T81 has a yield strength of 480 MPa (69.6 ksi) and a tensile strength of 530 MPa (76.9 ksi) — stronger than 95% of aluminum grades. Elongation at break is 8% and the elastic modulus is 78 GPa (11.3 Msi). 2099-T81 has a density of 2.63 g/cm³ (0.095 lb/in³), lighter than 95% of aluminum grades. It melts at 560°C (1,040 °F). T83 is the default condition FabDigit quotes; T81 is available on request or by drawing note.
Advantages
- High strength — 480 MPa (69.6 ksi), better than 95% of aluminum grades
- Tough — resists crack growth — 36 MPa·√m (32.8 ksi·√in), better than 93% of aluminum grades
Limitations
- Poor heat conductor — 115 W/m·K (66.4 BTU/hr·ft·°F), worse than 85% of aluminum grades
- Difficult to weld — 22/100, worse than 83% of aluminum grades
2099-T81 properties
Typical room-temperature values for 2099-T81; 20 are specific to this condition. Other listed values are 2099 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
2099-T81 has a density of 2.63 g/cm³ (0.095 lb/in³), lighter than 95% of aluminum grades. It melts at 560°C (1,040 °F).
Mechanical12
2099-T81 has a yield strength of 480 MPa (69.6 ksi) and a tensile strength of 530 MPa (76.9 ksi) — stronger than 95% of aluminum grades. Elongation at break is 8% and the elastic modulus is 78 GPa (11.3 Msi).
Thermal6
2099-T81 is rated for continuous service to 150°C (302 °F). It conducts heat at 115 W/m·K (66.4 BTU/hr·ft·°F), worse than 85% of aluminum grades. Thermal expansion is 21.9 µm/m·K (12.2 µin/in·°F).
Electrical3
2099-T81 conducts electricity at 31 % IACS, worse than 68% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (44/100), worse than 65% of aluminum grades.
Sustainability4
Producing a kilogram of 2099-T81 takes about 215 MJ of energy and emits 13.5 kg of CO₂ — more than 93% of aluminum grades. Typical recycled content is 5%.
Manufacturability6
2099-T81's machinability is good (64/100, better than 58% of aluminum grades); weldability poor (22/100); formability poor (24/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 2099-T81
Is 2099 easy to machine?
Machines much like 2024-T851: use sharp polished-flute carbide, high speed, generous flood coolant; expect springy thin webs and slightly abrasive Li/Cu phases — avoid dry cutting and keep chips out of water storage.
Can 2099 be welded?
Not suited to fusion welding (hot cracking, Li oxidation, porosity); join by riveting/bolting or by friction stir welding with qualified parameters.
Can 2099 be formed, bent or molded?
Bend, stretch-form and roll in the T3-type intermediate temper then age to T8; T83/T86 tolerate only large-radius work and are prone to delamination-type failure at sharp bends.
What surface finishes work on 2099?
Alkaline clean + deoxidize, then boric-sulfuric or chromic anodize (or Alodine-type conversion) plus epoxy primer; bare surfaces need protection in chloride service, and fasteners must be isolated to prevent galvanic pitting.
2099 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 |
|---|---|---|
| Cu | 2.4 – 3 | 2.7 |
| Liprimary density-reducing / stiffness-raising addition | 1.6 – 2 | 1.8 |
| Zn | 0.4 – 1 | 0.7 |
| Mn | 0.1 – 0.5 | 0.3 |
| Mg | 0.1 – 0.5 | 0.3 |
| Zrgrain-structure control (Al3Zr dispersoids) | 0.05 – 0.12 | 0.09 |
| Ti | ≤ 0.1 | — |
| Feimpurity limit | ≤ 0.07 | — |
| Siimpurity limit | ≤ 0.05 | — |
| Others (each)total 0.15 max | ≤ 0.05 | — |
| Al | balance | — |
2099-T81 — frequently asked
What is 2099-T81 used for?
2099-T81 is typically used for aircraft extrusions, wing ribs and spars, fuselage stringers, floor beams and seat tracks, machined forgings for airframe fittings and lower wing stringers and stiffeners. In short: low-density Al-Li extrusion alloy; high modulus for 2000 series; stringer and spar grade.
What is the yield strength of 2099-T81?
2099-T81 has a typical yield strength of 480 MPa (69.6 ksi) and a tensile strength of 530 MPa (76.9 ksi) — stronger than 95% of aluminum grades. Strength varies by condition: see the 6 listed tempers.
Is 2099-T81 easy to machine?
Reasonably — machinability is rated good (64/100, better than 58% of aluminum grades). Machines much like 2024-T851: use sharp polished-flute carbide, high speed, generous flood coolant; expect springy thin webs and slightly abrasive Li/Cu phases — avoid dry cutting and keep chips out of water storage.
Can 2099-T81 be welded?
Not readily — weldability is rated poor (22/100). Not suited to fusion welding (hot cracking, Li oxidation, porosity); join by riveting/bolting or by friction stir welding with qualified parameters.
What surface finishes work on 2099-T81?
Alkaline clean + deoxidize, then boric-sulfuric or chromic anodize (or Alodine-type conversion) plus epoxy primer; bare surfaces need protection in chloride service, and fasteners must be isolated to prevent galvanic pitting.
Can 2099-T81 be formed, bent or molded?
Bend, stretch-form and roll in the T3-type intermediate temper then age to T8; T83/T86 tolerate only large-radius work and are prone to delamination-type failure at sharp bends.
What is the maximum service temperature of 2099-T81?
2099-T81 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 2099-T83 and 2099-O?
T83 is the default condition — standard high-strength aerospace extrusion temper — pick for stringers, floor beams and rib/spar profiles. O: softest condition, used only as an intermediate mill/processing state for severe forming; not a service temper. Yield strength is 520 MPa in T83 versus 145 MPa in O.
Sources
- Registration Record of International Alloy Designations and Chemical Composition Limits for Wrought Aluminum Alloys (Teal Sheets) — The Aluminum Association (2018)
- AMS 4467 — Aluminum Alloy 2099 Extrusions, T83 Temper — SAE International (2016)
- 2099 Al-Li Extrusion Alloy Product Information — Alcoa / Arconic (2015)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Handbook Vol. 13B — Corrosion: Materials — ASM International (2005)
- MMPDS-style typical property compilations for Al-Li alloys — Battelle/FAA (2019)
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.