Aluminum 6261-O vs 6261-T651
Aluminum · 6261 temper comparison
6261-O and 6261-T651 are two conditions of the same aluminum grade, 6261: O (annealed) versus T651 (T6, stress relieved by stretching). The chemistry is identical, so every difference below comes from the condition. 6261-T651 is the stronger of the two: yield strength 295 MPa (42.8 ksi) against 65 MPa (9.43 ksi) for 6261-O, about 4.5 times as much; tensile strength follows at 325 MPa (47.1 ksi) vs 130 MPa (18.9 ksi). In exchange, 6261-O is the more ductile: elongation 25% versus 10% for 6261-T651, and 6261-T651 is harder (98 HB vs 32 HB). 6261-O runs hotter in service (200°C vs 150°C continuous) and 6261-O conducts heat better (190 W/m·K vs 170 W/m·K). On the shop floor, 6261-T651 machines more easily (good vs poor).
6261-OChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
6261-T651Choose it when strength drives the design, or when the part is machined in volume.
6261-O vs 6261-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)
Hardness, Brinell
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 70 GPa10.2 Msi · Shear Modulus 26 GPa3.8 Msi · Bulk Modulus 76 GPa11 Msi · Poisson's Ratio 0.33 · Fracture Toughness (K_IC) 29 MPa·√m26.4 ksi·√in
Physical
Density and transition temperatures.
Same in both: Density 2.7 g/cm³0.1 lb/in³ · Melting Point (Solidus) 585°C1,085 °F · Liquidus Temperature 650°C1,202 °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 896 J/kg·K0.21 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 23.4 µm/m·K13 µin/in·°F · Latent Heat of Fusion 393 J/g169 BTU/lb · Min Service Temperature -196°C-321 °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) -0.83 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: Castability 45 / 100 · Brazeability / Solderability 35 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 200 MJ/kg85,985 BTU/lb · Embodied Carbon (primary production) 12.5 kg CO₂/kg · Embodied Water 1,200 L/kg144 gal/lb · Typical Recycled Content 35%
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.
6261-O vs 6261-T651 — frequently asked
Is 6261-T651 stronger than 6261-O?
Yes. 6261-T651 has a typical yield strength of 295 MPa (42.8 ksi) against 65 MPa (9.43 ksi) for 6261-O — about 4.5 times as much. Tensile strength is 325 MPa (47.1 ksi) vs 130 MPa (18.9 ksi).
Which condition does FabDigit quote by default, O or T651?
T6 is the default 6261 condition in the FabDigit quote flow (neither O 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, 6261-O or 6261-T651?
6261-T651. Its machinability rates good (58/100) against poor (30/100) for 6261-O; for welding the order is 6261-O first (very good, 75/100) then 6261-T651 (good, 68/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 6261-O and 6261-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.