Aluminum 2A21-O vs 2A21-T4
Aluminum · 2A21 temper comparison
2A21-O and 2A21-T4 are two conditions of the same aluminum grade, 2A21: O (annealed) versus T4 (solution heat treated and naturally aged). The chemistry is identical, so every difference below comes from the condition. 2A21-T4 is the stronger of the two: yield strength 210 MPa (30.5 ksi) against 80 MPa (11.6 ksi) for 2A21-O, about 163% more; tensile strength follows at 350 MPa (50.8 ksi) vs 175 MPa (25.4 ksi). In exchange, 2A21-O is the more ductile: elongation 18% versus 16% for 2A21-T4, and 2A21-T4 is harder (100 HB vs 45 HB). 2A21-O runs hotter in service (250°C vs 175°C continuous) and 2A21-O conducts heat better (170 W/m·K vs 116 W/m·K). On the shop floor, 2A21-T4 machines more easily (good vs fair).
2A21-OChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
2A21-T4Choose it when strength drives the design, or when the part is machined in volume.
2A21-O vs 2A21-T4: 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 73 GPa10.6 Msi · Shear Modulus 27 GPa3.9 Msi · Bulk Modulus 75 GPa10.9 Msi · Poisson's Ratio 0.33 · Reduction in Area 30% · Fatigue Strength (Endurance Limit) 100 MPa14.5 ksi · Fracture Toughness (K_IC) 32 MPa·√m29.1 ksi·√in · Hardness, Vickers 108 HV
Physical
Density and transition temperatures.
Same in both: Density 2.84 g/cm³0.1 lb/in³ · Melting Point (Solidus) 543°C1,009 °F · Liquidus Temperature 643°C1,189 °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 864 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 389 J/g167 BTU/lb · Min Service Temperature -196°C-321 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Same in both: Electrical Resistivity 6.2×10⁻⁸ Ω·m2.44 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.66 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 %) 50% · Weldability 60 / 100 · Brazeability / Solderability 15 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 210 MJ/kg90,284 BTU/lb · Embodied Carbon (primary production) 12.5 kg CO₂/kg · Embodied Water 1,100 L/kg132 gal/lb · Typical Recycled Content 15%
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.
2A21-O vs 2A21-T4 — frequently asked
Is 2A21-T4 stronger than 2A21-O?
Yes. 2A21-T4 has a typical yield strength of 210 MPa (30.5 ksi) against 80 MPa (11.6 ksi) for 2A21-O — about 163% more. Tensile strength is 350 MPa (50.8 ksi) vs 175 MPa (25.4 ksi).
Which condition does FabDigit quote by default, O or T4?
T4 is the default 2A21 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, 2A21-O or 2A21-T4?
2A21-T4. Its machinability rates good (58/100) against fair (40/100) for 2A21-O.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 2A21-O and 2A21-T4 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.