Aluminum 2099-O (Annealed)
Temper
AA 2099 · UNS A92099
Softest condition, used only as an intermediate mill/processing state for severe forming; not a service temper.
Values for the O 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 |
|---|---|---|---|---|---|---|
OThis page 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 |
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-O?
2099-O is 2099 in the O temper — softest condition, used only as an intermediate mill/processing state for severe forming; not a service temper. 2099-O has a yield strength of 145 MPa (21 ksi) and a tensile strength of 270 MPa (39.2 ksi) — weaker than 68% of aluminum grades. Elongation at break is 18% and the elastic modulus is 78 GPa (11.3 Msi). 2099-O 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; O is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 45 MPa·√m (41 ksi·√in), better than 100% of aluminum grades
- Ductile — tolerates forming and impact — 18%, better than 86% of aluminum grades
- Forms and bends easily — 70/100, better than 83% of aluminum grades
2099-O properties
Typical room-temperature values for 2099-O; 22 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-O 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-O has a yield strength of 145 MPa (21 ksi) and a tensile strength of 270 MPa (39.2 ksi) — weaker than 68% of aluminum grades. Elongation at break is 18% and the elastic modulus is 78 GPa (11.3 Msi).
Thermal6
2099-O is rated for continuous service to 150°C (302 °F). It conducts heat at 126 W/m·K (72.8 BTU/hr·ft·°F), worse than 70% of aluminum grades. Thermal expansion is 21.9 µm/m·K (12.2 µin/in·°F).
Electrical3
2099-O conducts electricity at 34 % IACS, worse than 52% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (50/100), worse than 56% of aluminum grades.
Sustainability4
Producing a kilogram of 2099-O 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-O's machinability is fair (45/100, worse than 72% of aluminum grades); weldability poor (33/100); formability very good (70/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 2099-O
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-O — frequently asked
What is 2099-O used for?
2099-O 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-O?
2099-O has a typical yield strength of 145 MPa (21 ksi) and a tensile strength of 270 MPa (39.2 ksi) — weaker than 68% of aluminum grades. Strength varies by condition: see the 6 listed tempers.
Is 2099-O easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 72% 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-O be welded?
Not readily — weldability is rated poor (33/100). 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-O?
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-O 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-O?
2099-O 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.