Aluminum 6181-O vs 6181-T61
Aluminum · 6181 temper comparison
6181-O and 6181-T61 are two conditions of the same aluminum grade, 6181: O (annealed) versus T61 (T6 variant, underaged). The chemistry is identical, so every difference below comes from the condition. 6181-T61 is the stronger of the two: yield strength 235 MPa (34.1 ksi) against 60 MPa (8.7 ksi) for 6181-O, about 3.9 times as much; tensile strength follows at 290 MPa (42.1 ksi) vs 125 MPa (18.1 ksi). In exchange, 6181-O is the more ductile: elongation 28% versus 14% for 6181-T61, and 6181-T61 is harder (88 HB vs 33 HB). 6181-T61 runs hotter in service (150°C vs 120°C continuous). On the shop floor, 6181-T61 machines more easily (good vs fair).
6181-OChoose it when the part is bent, formed or impact-loaded.
6181-T61Choose it when strength drives the design, or when the part sees heat.
6181-O vs 6181-T61: 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
Shear Strength
Fatigue Strength (Endurance Limit)
Hardness, Brinell
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 69 GPa10 Msi · Shear Modulus 26 GPa3.8 Msi · Bulk Modulus 69 GPa10 Msi · Poisson's Ratio 0.33
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 900 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 395 J/g170 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) -0.74 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Weldability
Formability (cold)
Same in both: Brazeability / Solderability 40 / 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 kg CO₂/kg · Embodied Water 1,200 L/kg144 gal/lb · Typical Recycled Content 30%
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.
6181-O vs 6181-T61 — frequently asked
Is 6181-T61 stronger than 6181-O?
Yes. 6181-T61 has a typical yield strength of 235 MPa (34.1 ksi) against 60 MPa (8.7 ksi) for 6181-O — about 3.9 times as much. Tensile strength is 290 MPa (42.1 ksi) vs 125 MPa (18.1 ksi).
Which condition does FabDigit quote by default, O or T61?
Specify the condition in the material field or the drawing note; FabDigit prices the quote for the state you call out.
Which is easier to machine, 6181-O or 6181-T61?
6181-T61. Its machinability rates good (65/100) against fair (40/100) for 6181-O; for welding the order is 6181-O first (very good, 78/100) then 6181-T61 (very good, 70/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 6181-O and 6181-T61 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.