Aluminum 2091-T851
Temper
AA 2091 · UNS A92091
T851 = t8, stress relieved by stretching
Peak-aged, low-residual-stress plate for machined structural parts; watch short-transverse ductility and SCC.
Values for the T851 condition
Other 2091 tempers and conditions
2091 is listed in 6 conditions; see the grade overview at 2091.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest condition for forming and intermediate processing; must be re-solution treated and aged for service. | 145 | 260 | 22 | 65 HB | 23 % IACS |
Solution heat treated, cold worked and naturally aged | Damage-tolerant sheet condition, the direct low-density counterpart to 2024-T3 fuselage skin. | 240 | 395 | 22 | 100 HB | 17 % IACS |
T3, stress relieved by stretching | Plate condition with low residual stress for machined parts that will be aged later or used as-is for toughness. | 250 | 400 | 18 | 103 HB | 17 % IACS |
T8XDefault Solution heat treated, cold worked and artificially aged | Standard supplied condition for 2091 aerospace sheet: best combination of strength, toughness and fatigue-crack resistance at low density. | 370 | 450 | 10 | 125 HB | 19 % IACS |
Solution heat treated, cold worked and artificially aged to higher… | Higher-strength ageing variant of the T8 route when static strength outweighs toughness. | 390 | 465 | 8 | 132 HB | 20 % IACS |
T851This page T8, stress relieved by stretching | Peak-aged, low-residual-stress plate for machined structural parts; watch short-transverse ductility and SCC. | 405 | 470 | 6 | 135 HB | 20 % IACS |
What is 2091-T851?
2091-T851 is 2091 in the T851 temper — peak-aged, low-residual-stress plate for machined structural parts; watch short-transverse ductility and SCC. 2091-T851 has a yield strength of 405 MPa (58.7 ksi) and a tensile strength of 470 MPa (68.2 ksi) — stronger than 88% of aluminum grades. Elongation at break is 6% and the elastic modulus is 76 GPa (11 Msi). 2091-T851 has a density of 2.58 g/cm³ (0.0932 lb/in³), lighter than 98% of aluminum grades. It melts at 560°C (1,040 °F). T8X is the default condition FabDigit quotes; T851 is available on request or by drawing note.
Advantages
- High strength — 405 MPa (58.7 ksi), better than 88% of aluminum grades
- Tough — resists crack growth — 30 MPa·√m (27.3 ksi·√in), better than 76% of aluminum grades
Limitations
- Low electrical conductivity — 20 % IACS, worse than 99% of aluminum grades
- High embodied carbon — 14.5 kg CO₂/kg, worse than 97% of aluminum grades
- Poor heat conductor — 100 W/m·K (57.8 BTU/hr·ft·°F), worse than 93% of aluminum grades
- Needs corrosion protection — 35/100, worse than 85% of aluminum grades
- Limited service temperature — 120°C (248 °F), worse than 79% of aluminum grades
2091-T851 properties
Typical room-temperature values for 2091-T851; 20 are specific to this condition. Other listed values are 2091 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
2091-T851 has a density of 2.58 g/cm³ (0.0932 lb/in³), lighter than 98% of aluminum grades. It melts at 560°C (1,040 °F).
Mechanical11
2091-T851 has a yield strength of 405 MPa (58.7 ksi) and a tensile strength of 470 MPa (68.2 ksi) — stronger than 88% of aluminum grades. Elongation at break is 6% and the elastic modulus is 76 GPa (11 Msi).
Thermal6
2091-T851 is rated for continuous service to 120°C (248 °F). It conducts heat at 100 W/m·K (57.8 BTU/hr·ft·°F), worse than 93% of aluminum grades. Thermal expansion is 23 µm/m·K (12.8 µin/in·°F).
Electrical3
2091-T851 conducts electricity at 20 % IACS, worse than 99% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (35/100), worse than 85% of aluminum grades.
Sustainability4
Producing a kilogram of 2091-T851 takes about 225 MJ of energy and emits 14.5 kg of CO₂ — more than 96% of aluminum grades. Typical recycled content is 5%.
Manufacturability7
2091-T851's machinability is very good (70/100, better than 72% of aluminum grades); weldability poor (25/100); formability poor (22/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 2091-T851
Is 2091 easy to machine?
Machines like 2024-T3 with sharp carbide tools, high speed and flood coolant; fine Li-bearing chips/dust are reactive — avoid dry grinding and collect swarf wet.
Can 2091 be welded?
Poor fusion weldability (Li oxide films, hydrogen porosity, hot cracking); join by riveting, bonding or friction stir welding rather than TIG/MIG.
Can 2091 be formed, bent or molded?
Form in O or T3 condition; T8X sheet has limited bendability and marked anisotropy, so orient bends relative to rolling direction and use generous radii or hot/creep forming.
What surface finishes work on 2091?
Chromic or sulfuric acid anodize plus chromate-free primer for aerospace protection; cladding or coating is essentially mandatory since bare surfaces pit and exfoliate in chloride service.
2091 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 |
|---|---|---|
| Liprincipal density-reducing / δ' strengthening element | 1.7 – 2.3 | 2 |
| Cu | 1.8 – 2.5 | 2.1 |
| Mg | 1.1 – 1.9 | 1.5 |
| Zrgrain-structure control | 0.04 – 0.16 | 0.1 |
| Si | ≤ 0.2 | — |
| Fe | ≤ 0.3 | — |
| Mn | ≤ 0.1 | — |
| Cr | ≤ 0.1 | — |
| Zn | ≤ 0.25 | — |
| Ti | ≤ 0.1 | — |
| Others (each) | ≤ 0.05 | — |
| Others (total) | ≤ 0.15 | — |
| Al | balance | — |
2091-T851 — frequently asked
What is 2091-T851 used for?
2091-T851 is typically used for aerospace sheet skins, secondary airframe structure, formed sheet brackets and clips, riveted panel assemblies, interior structural sheet parts and weight-reduction sheet substitutions. In short: european first-generation Al-Li; best-machining Al-Li sheet; requires cladding or coating.
What is the yield strength of 2091-T851?
2091-T851 has a typical yield strength of 405 MPa (58.7 ksi) and a tensile strength of 470 MPa (68.2 ksi) — stronger than 88% of aluminum grades. Strength varies by condition: see the 6 listed tempers.
Is 2091-T851 easy to machine?
Yes — machinability is rated very good (70/100, better than 72% of aluminum grades). Machines like 2024-T3 with sharp carbide tools, high speed and flood coolant; fine Li-bearing chips/dust are reactive — avoid dry grinding and collect swarf wet.
Can 2091-T851 be welded?
Not readily — weldability is rated poor (25/100). Poor fusion weldability (Li oxide films, hydrogen porosity, hot cracking); join by riveting, bonding or friction stir welding rather than TIG/MIG.
What surface finishes work on 2091-T851?
Chromic or sulfuric acid anodize plus chromate-free primer for aerospace protection; cladding or coating is essentially mandatory since bare surfaces pit and exfoliate in chloride service.
Can 2091-T851 be formed, bent or molded?
Form in O or T3 condition; T8X sheet has limited bendability and marked anisotropy, so orient bends relative to rolling direction and use generous radii or hot/creep forming.
What is the maximum service temperature of 2091-T851?
2091-T851 is rated for continuous use to about 120°C (248 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 2091-T8X and 2091-O?
T8X is the default condition — standard supplied condition for 2091 aerospace sheet: best combination of strength, toughness and fatigue-crack resistance at low density. O: softest condition for forming and intermediate processing; must be re-solution treated and aged for service. Yield strength is 370 MPa in T8X versus 145 MPa in O.
Sources
- International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets) — The Aluminum Association (2018)
- ASM Handbook Vol. 2: Properties and Selection — Nonferrous Alloys and Special-Purpose Materials (Al-Li alloys) — ASM International (1990)
- Aluminum-Lithium Alloys: Processing, Properties and Applications — Butterworth-Heinemann/Elsevier (2014)
- Pechiney/Cegedur 2091 Al-Li aerospace sheet data — Pechiney (now Constellium) (1990)
- MMPDS / MIL-HDBK-5 background data on 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.