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Aluminum 2024-T351 vs. Steel AISI 4340

Compare Aluminum 2024-T351 vs. Steel AISI 4340 strength, stiffness, weight and thermal properties.

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Aluminum 2024-T351Wrought
Steel AISI 4340Wrought
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Mechanical
Yield strength324MPasourcetypical, 0.2% offset, .500 in dia specimen1,035MPasourcetypical, transverse
Ultimate tensile strength469MPasourcetypical1,140MPasourcetypical, transverse
Elongation at break19%sourcetypical, in 4D18%sourcetypical, transverse
Young's modulus (stiffness)73.1GPasourcetypical200GPasourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered)
Density2,770kg/m³sourcenominal7,840kg/m³sourcetypical
Strength to weight117kN·m/kg132kN·m/kg13% higher
Stiffness to weight26.4MN·m/kg4% higher25.5MN·m/kg
Poisson's ratio0.33sourcetypical (handbook physical constant), all tempers0.32sourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered)
Shear modulus27.5GPa75.7GPa2.76x stiffer in shear
Bulk modulus71.7GPa185GPa
Speed of sound5,137m/s5,049m/s
Thermal
Thermal conductivity120W/m·Ksourcetypical, 20 °C37.5W/m·Ksourcetypical
Thermal expansion22.9µm/m·Ksourcetypical, mean 20-100 °C11.3µm/m·Ksourcemean, -18 to 93 °C
100 mm part over a 50 °C swing115µm growth56.5µm growth2.03x less
Specific heat875J/kg·Ksourcetypical, at 100 °C448J/kg·Ksourcetypical
Heats up and cools (diffusivity)49.5mm²/s4.64x faster10.7mm²/s
Thermal shock resistance15,561W/m33% more resistant11,678W/m
Melting point502–638°Csourcemelting rangenot sourced
Values for2024-T4/T351, Kaiser Aluminum sheet, coil & plate typical datasheet; Poisson from MIL-HDBK-5JCarpenter (Latrobe) Lescalloy 4340 VAC-ARC datasheet; mechanical row for 1100 °F temper; physical properties grade-level

Every value links to the document that states it. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.

Questions

Is Aluminum 2024-T351 stronger than Steel AISI 4340?

Steel AISI 4340 is stronger: its yield strength is 1,035 MPa against 324 MPa for Aluminum 2024-T351 (3.19x).

Which is lighter, Aluminum 2024-T351 or Steel AISI 4340?

Aluminum 2024-T351 is lighter: 2,770 kg/m³ against 7,840 kg/m³ for Steel AISI 4340.

Which is stiffer, Aluminum 2024-T351 or Steel AISI 4340?

Steel AISI 4340 is stiffer: Young's modulus 200 GPa against 73.1 GPa for Aluminum 2024-T351, so the same part in Steel AISI 4340 deflects less under the same load.

Which is lighter for the same job, Aluminum 2024-T351 or Steel AISI 4340?

For the same stiffness or strength: Aluminum 2024-T351 is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong beam, strong panel or plate; Steel AISI 4340 is lighter for a strong rod or tie.

Part that must beAluminum 2024-T351Steel AISI 4340
Stiff rod or tie (tension)lighter4% heavier
Stiff beam (bending)lighter1.71x heavier
Stiff panel or platelighter2.02x heavier
Strong rod or tie13% heavierlighter
Strong beamlighter30% heavier
Strong panel or platelighter1.58x heavier

For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).

Which conducts heat better, Aluminum 2024-T351 or Steel AISI 4340?

Aluminum 2024-T351 conducts heat better: 120 W/m·K against 37.5 W/m·K for Steel AISI 4340.

Which expands less with temperature?

Steel AISI 4340 expands less: 11.3 µm/m·K against 22.9 µm/m·K for Aluminum 2024-T351.

Among 59 materials

1k10k0.1110100Density (kg/m³)Young's modulus (GPa)Plastic PLAPlastic PETGPlastic ABSPlastic TPUPlastic NylonAluminumSteelIronTitaniumSteel AISI 1018Stainless 304Stainless 316Aluminum 6061-T6Aluminum 7075-T6Brass C360Copper C110GlassSteel AISI 1045Steel A992Stainless 303Stainless 17-4PHAluminum 5052-H32Aluminum 7050-T7451Titanium Ti-6Al-4VBrass C260Nickel Inconel 718Magnesium AZ31B-H24Zinc Zamak 3Plastic ABS (bulk/injection)Plastic PolycarbonatePlastic POM/AcetalPlastic Nylon PA6Plastic Nylon PA66Plastic PEEKPlastic UHMWPEPlastic HDPEPlastic PolypropylenePlastic PMMAFDM ASAFDM PolycarbonateFDM PAHT-CFFDM HIPSSLA Resin Tough 2000SLS PA12 NylonDMLS AlSi10Mg AluminumDMLS Ti-6Al-4V ELI TitaniumDMLS 316L Stainless SteelDMLS 17-4PH Stainless SteelAluminum 2024-T351Steel AISI 4340
Stiffness against density
1k10k101001kDensity (kg/m³)Yield strength (MPa)Plastic PLAPlastic PETGPlastic ABSPlastic TPUPlastic NylonRubberAluminumSteelIronTitaniumSteel AISI 1018Stainless 304Stainless 316Aluminum 6061-T6Aluminum 7075-T6Brass C360Copper C110GlassSteel AISI 1045Steel A992Stainless 303Stainless 17-4PHAluminum 5052-H32Aluminum 7050-T7451Titanium Ti-6Al-4VBrass C260Nickel Inconel 718Magnesium AZ31B-H24Zinc Zamak 3Plastic ABS (bulk/injection)Plastic PolycarbonatePlastic POM/AcetalPlastic Nylon PA6Plastic Nylon PA66Plastic PEEKPlastic PTFEPlastic UHMWPEPlastic HDPEPlastic PolypropylenePlastic PMMAFDM ASAFDM PolycarbonateFDM PAHT-CFFDM HIPSSLA Resin Tough 2000SLA Resin Elastic 50ASLS PA12 NylonDMLS AlSi10Mg AluminumDMLS Ti-6Al-4V ELI TitaniumDMLS 316L Stainless SteelDMLS 17-4PH Stainless SteelBrickAluminum 2024-T351Steel AISI 4340
Strength against density

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