Aluminum 2139-T4 vs 2139-T851
Aluminum · 2139 temper comparison
2139-T4 and 2139-T851 are two conditions of the same aluminum grade, 2139: T4 (solution heat treated and naturally aged) versus T851 (T8, stress relieved by stretching). The chemistry is identical, so every difference below comes from the condition. 2139-T851 is the stronger of the two: yield strength 448 MPa (65 ksi) against 275 MPa (39.9 ksi) for 2139-T4, about 63% more; tensile strength follows at 480 MPa (69.6 ksi) vs 430 MPa (62.4 ksi). In exchange, 2139-T4 is the more ductile: elongation 20% versus 10% for 2139-T851, and 2139-T851 is harder (134 HB vs 115 HB). 2139-T851 runs hotter in service (150°C vs 100°C continuous) and 2139-T851 conducts heat better (152 W/m·K vs 122 W/m·K).
2139-T4Choose it when the part is bent, formed or impact-loaded.
2139-T851Choose it when strength drives the design, or when the part sees heat.
2139-T4 vs 2139-T851: 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)
Fracture Toughness (K_IC)
Hardness, Brinell
Same in both: Elastic (Young's) Modulus 72 GPa10.4 Msi · Shear Modulus 27 GPa3.9 Msi · Bulk Modulus 71 GPa10.3 Msi · Poisson's Ratio 0.33 · Compressive Strength 455 MPa66 ksi
Physical
Density and transition temperatures.
Same in both: Density 2.85 g/cm³0.1 lb/in³ · Melting Point (Solidus) 507°C945 °F · Liquidus Temperature 641°C1,186 °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 875 J/kg·K0.21 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 22.7 µm/m·K12.6 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
Same in both: Electrical Resistivity 4.7×10⁻⁸ Ω·m1.85 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.72 V · Corrosion Resistance 32 / 100
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 %) 70% · Weldability 20 / 100 · Castability 30 / 100 · Brazeability / Solderability 15 / 100 · Polishability 55 / 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 1,100 L/kg132 gal/lb · Typical Recycled Content 12%
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.
2139-T4 vs 2139-T851 — frequently asked
Is 2139-T851 stronger than 2139-T4?
Yes. 2139-T851 has a typical yield strength of 448 MPa (65 ksi) against 275 MPa (39.9 ksi) for 2139-T4 — about 63% more. Tensile strength is 480 MPa (69.6 ksi) vs 430 MPa (62.4 ksi).
Which condition does FabDigit quote by default, T4 or T851?
T8 is the default 2139 condition in the FabDigit quote flow (neither T4 nor T851). 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, 2139-T4 or 2139-T851?
2139-T851. Its machinability rates very good (74/100) against good (65/100) for 2139-T4.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 2139-T4 and 2139-T851 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.