Aluminum 7040-O vs 7040-T651
Aluminum · 7040 temper comparison
7040-O and 7040-T651 are two conditions of the same aluminum grade, 7040: O (annealed) versus T651 (T6, stress relieved by stretching). The chemistry is identical, so every difference below comes from the condition. 7040-T651 is the stronger of the two: yield strength 505 MPa (73.2 ksi) against 115 MPa (16.7 ksi) for 7040-O, about 4.4 times as much; tensile strength follows at 565 MPa (81.9 ksi) vs 250 MPa (36.3 ksi). In exchange, 7040-O is the more ductile: elongation 15% versus 8% for 7040-T651, and 7040-T651 is harder (163 HB vs 65 HB). 7040-O runs hotter in service (150°C vs 100°C continuous) and 7040-O conducts heat better (178 W/m·K vs 131 W/m·K). On the shop floor, 7040-T651 machines more easily (very good vs fair).
7040-OChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
7040-T651Choose it when strength drives the design, or when the part is machined in volume.
7040-O vs 7040-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
Shear Strength
Fracture Toughness (K_IC)
Hardness, Brinell
Same in both: Elastic (Young's) Modulus 71 GPa10.3 Msi · Shear Modulus 26.9 GPa3.9 Msi · Bulk Modulus 75 GPa10.9 Msi · Poisson's Ratio 0.33 · Compressive Strength 465 MPa67.4 ksi · Fatigue Strength (Endurance Limit) 160 MPa23.2 ksi
Physical
Density and transition temperatures.
Same in both: Density 2.82 g/cm³0.1 lb/in³ · Melting Point (Solidus) 480°C896 °F · Liquidus Temperature 635°C1,175 °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) 23.4 µm/m·K13 µin/in·°F · Latent Heat of Fusion 390 J/g168 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) -0.84 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Formability (cold)
Same in both: Machinability Rating (AISI 1212 = 100 %) 90% · Weldability 20 / 100 · Brazeability / Solderability 10 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 205 MJ/kg88,134 BTU/lb · Embodied Carbon (primary production) 12.5 kg CO₂/kg · Embodied Water 1,200 L/kg144 gal/lb · Typical Recycled Content 10%
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.
7040-O vs 7040-T651 — frequently asked
Is 7040-T651 stronger than 7040-O?
Yes. 7040-T651 has a typical yield strength of 505 MPa (73.2 ksi) against 115 MPa (16.7 ksi) for 7040-O — about 4.4 times as much. Tensile strength is 565 MPa (81.9 ksi) vs 250 MPa (36.3 ksi).
Which condition does FabDigit quote by default, O or T651?
T7451 is the default 7040 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, 7040-O or 7040-T651?
7040-T651. Its machinability rates very good (72/100) against fair (40/100) for 7040-O.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 7040-O and 7040-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.