Aluminum 8091-T3 vs 8091-T651
Aluminum · 8091 temper comparison
8091-T3 and 8091-T651 are two conditions of the same aluminum grade, 8091: T3 (solution heat treated, cold worked and naturally aged) versus T651 (T6, stress relieved by stretching). The chemistry is identical, so every difference below comes from the condition. 8091-T651 is the stronger of the two: yield strength 455 MPa (66 ksi) against 285 MPa (41.3 ksi) for 8091-T3, about 60% more; tensile strength follows at 515 MPa (74.7 ksi) vs 400 MPa (58 ksi). In exchange, 8091-T3 is the more ductile: elongation 12% versus 5% for 8091-T651, and 8091-T651 is harder (150 HB vs 115 HB). 8091-T651 conducts heat better (95 W/m·K vs 85 W/m·K). On the shop floor, 8091-T651 machines more easily (65 vs 55 out of 100).
8091-T3Choose it when the part is bent, formed or impact-loaded.
8091-T651Choose it when strength drives the design, or when the part is machined in volume.
8091-T3 vs 8091-T651: 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.
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Hardness, Brinell
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 80 GPa11.6 Msi · Shear Modulus 30 GPa4.4 Msi · Bulk Modulus 76 GPa11 Msi · Poisson's Ratio 0.34
Physical
Density and transition temperatures.
Same in both: Density 2.55 g/cm³0.09 lb/in³ · Melting Point (Solidus) 570°C1,058 °F · Liquidus Temperature 650°C1,202 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Same in both: Specific Heat Capacity 900 J/kg·K0.21 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 21.4 µm/m·K11.9 µin/in·°F · Latent Heat of Fusion 390 J/g168 BTU/lb · Max Service Temperature (continuous) 120°C248 °F · 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) -0.73 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Same in both: Brazeability / Solderability 10 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 260 MJ/kg111,780 BTU/lb · Embodied Carbon (primary production) 18 kg CO₂/kg · Embodied Water 1,200 L/kg144 gal/lb · Typical Recycled Content 3%
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.
8091-T3 vs 8091-T651 — frequently asked
Is 8091-T651 stronger than 8091-T3?
Yes. 8091-T651 has a typical yield strength of 455 MPa (66 ksi) against 285 MPa (41.3 ksi) for 8091-T3 — about 60% more. Tensile strength is 515 MPa (74.7 ksi) vs 400 MPa (58 ksi).
Which condition does FabDigit quote by default, T3 or T651?
T851 is the default 8091 condition in the FabDigit quote flow (neither T3 nor T651). 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, 8091-T3 or 8091-T651?
8091-T651, by a small margin. Both rate good for machinability — 65/100 against 55/100 for 8091-T3; for welding the order is 8091-T3 first (poor, 25/100) then 8091-T651 (poor, 20/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 8091-T3 and 8091-T651 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.