Aluminum 2018-O vs 2018-T61
Aluminum · 2018 temper comparison
2018-O and 2018-T61 are two conditions of the same aluminum grade, 2018: O (annealed) versus T61 (T6 variant, underaged). The chemistry is identical, so every difference below comes from the condition. 2018-T61 is the stronger of the two: yield strength 315 MPa (45.7 ksi) against 70 MPa (10.2 ksi) for 2018-O, about 4.5 times as much; tensile strength follows at 420 MPa (60.9 ksi) vs 140 MPa (20.3 ksi). In exchange, 2018-O is the more ductile: elongation 20% versus 12% for 2018-T61, and 2018-T61 is harder (120 HB vs 45 HB). 2018-O conducts heat better (172 W/m·K vs 154 W/m·K). On the shop floor, 2018-T61 machines more easily (very good vs fair).
2018-OChoose it when the part is bent, formed or impact-loaded.
2018-T61Choose it when strength drives the design, or when the part is machined in volume.
2018-O vs 2018-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
Hardness, Brinell
Same in both: Elastic (Young's) Modulus 74 GPa10.7 Msi · Shear Modulus 28 GPa4.1 Msi · Bulk Modulus 76 GPa11 Msi · Poisson's Ratio 0.33 · Compressive Strength 320 MPa46.4 ksi · Fatigue Strength (Endurance Limit) 115 MPa16.7 ksi · Fracture Toughness (K_IC) 22 MPa·√m20 ksi·√in · Hardness, Vickers 128 HV
Physical
Density and transition temperatures.
Same in both: Density 2.8 g/cm³0.1 lb/in³ · Melting Point (Solidus) 507°C945 °F · Liquidus Temperature 638°C1,180 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Same in both: Specific Heat Capacity 875 J/kg·K0.21 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 22.3 µm/m·K12.4 µin/in·°F · Latent Heat of Fusion 390 J/g168 BTU/lb · Max Service Temperature (continuous) 200°C392 °F · Min Service Temperature -196°C-321 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Same in both: Electrical Resistivity 4.31×10⁻⁸ Ω·m1.7 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.7 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Formability (cold)
Same in both: Weldability 22 / 100 · Brazeability / Solderability 15 / 100 · Polishability 50 / 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 20%
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.
2018-O vs 2018-T61 — frequently asked
Is 2018-T61 stronger than 2018-O?
Yes. 2018-T61 has a typical yield strength of 315 MPa (45.7 ksi) against 70 MPa (10.2 ksi) for 2018-O — about 4.5 times as much. Tensile strength is 420 MPa (60.9 ksi) vs 140 MPa (20.3 ksi).
Which condition does FabDigit quote by default, O or T61?
T61 is the default 2018 condition in the FabDigit quote flow. 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, 2018-O or 2018-T61?
2018-T61. Its machinability rates very good (72/100) against fair (45/100) for 2018-O.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 2018-O and 2018-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.