Aluminum 2091-O vs 2091-T851
Aluminum · 2091 temper comparison
2091-O and 2091-T851 are two conditions of the same aluminum grade, 2091: O (annealed) versus T851 (T8, stress relieved by stretching). The chemistry is identical, so every difference below comes from the condition. 2091-T851 is the stronger of the two: yield strength 405 MPa (58.7 ksi) against 145 MPa (21 ksi) for 2091-O, about 179% more; tensile strength follows at 470 MPa (68.2 ksi) vs 260 MPa (37.7 ksi). In exchange, 2091-O is the more ductile: elongation 22% versus 6% for 2091-T851, and 2091-T851 is harder (135 HB vs 65 HB). 2091-T851 runs hotter in service (120°C vs 100°C continuous) and 2091-O conducts heat better (115 W/m·K vs 100 W/m·K). On the shop floor, 2091-T851 machines more easily (very good vs fair).
2091-OChoose it when the part is bent, formed or impact-loaded.
2091-T851Choose it when strength drives the design, or when the part sees heat.
2091-O vs 2091-T851: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all aluminum grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all aluminum grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Hardness, Brinell
Same in both: Shear Modulus 28.5 GPa4.1 Msi · Bulk Modulus 76 GPa11 Msi · Poisson's Ratio 0.34
Physical
Density and transition temperatures.
Same in both: Density 2.58 g/cm³0.09 lb/in³ · Melting Point (Solidus) 560°C1,040 °F · Liquidus Temperature 655°C1,211 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 860 J/kg·K0.21 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 23 µm/m·K12.8 µin/in·°F · Latent Heat of Fusion 390 J/g168 BTU/lb · Min Service Temperature -253°C-423 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.72 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Formability (cold)
Same in both: Weldability 25 / 100 · Brazeability / Solderability 10 / 100 · Polishability 55 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 225 MJ/kg96,733 BTU/lb · Embodied Carbon (primary production) 14.5 kg CO₂/kg · Embodied Water 1,200 L/kg144 gal/lb · Typical Recycled Content 5%
Strength versus weight
Yield strength against density for every aluminum grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
2091-O vs 2091-T851 — frequently asked
Is 2091-T851 stronger than 2091-O?
Yes. 2091-T851 has a typical yield strength of 405 MPa (58.7 ksi) against 145 MPa (21 ksi) for 2091-O — about 179% more. Tensile strength is 470 MPa (68.2 ksi) vs 260 MPa (37.7 ksi).
Which condition does FabDigit quote by default, O or T851?
T8X is the default 2091 condition in the FabDigit quote flow (neither O nor T851). The other condition is available on request or by drawing note — specify it in the material field or the part notes and the quote is priced for it.
Which is easier to machine, 2091-O or 2091-T851?
2091-T851. Its machinability rates very good (70/100) against fair (45/100) for 2091-O.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 2091-O and 2091-T851 side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.