Materials / Compare
Aluminum 7075-T6 vs. Steel AISI 4340
Compare Aluminum 7075-T6 vs. Steel AISI 4340 strength, stiffness, weight and thermal properties.
| Try it on a partA bracket to run stress or thermal on, free in your browser | Open in LessCAD | Open in LessCAD |
|---|---|---|
| Mechanical | ||
| Yield strength | 503MPasourcetypical, 0.2% offset, .500 in dia specimen | 1,035MPasourcetypical, transverse |
| Ultimate tensile strength | 572MPasourcetypical | 1,140MPasourcetypical, transverse |
| Elongation at break | 11%sourcetypical, in 4D | 18%sourcetypical, transverse |
| Young's modulus (stiffness) | 71GPasourcetypical | 200GPasourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) |
| Density | 2,800kg/m³sourcenominal | 7,840kg/m³sourcetypical |
| Strength to weight | 180kN·m/kg36% higher | 132kN·m/kg |
| Stiffness to weight | 25.4MN·m/kg | 25.5MN·m/kg |
| Poisson's ratio | 0.33sourcetypical (handbook physical constant) | 0.32sourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) |
| Shear modulus | 26.7GPa | 75.7GPa2.84x stiffer in shear |
| Bulk modulus | 69.6GPa | 185GPa |
| Speed of sound | 5,036m/s | 5,049m/s |
| Thermal | ||
| Thermal conductivity | 130W/m·Ksourcetypical, 20 °C, T651 | 37.5W/m·Ksourcetypical |
| Thermal expansion | 23.4µm/m·Ksourcetypical, mean 20-100 °C | 11.3µm/m·Ksourcemean, -18 to 93 °C |
| 100 mm part over a 50 °C swing | 117µm growth | 56.5µm growth2.07x less |
| Specific heat | 960J/kg·Ksourcetypical, at 100 °C | 448J/kg·Ksourcetypical |
| Heats up and cools (diffusivity) | 48.4mm²/s4.53x faster | 10.7mm²/s |
| Thermal shock resistance | 26,370W/m2.26x more resistant | 11,678W/m |
| Melting point | 532–635°Csourcemelting range | not sourced |
| Values for | 7075-T6/T651, Kaiser Aluminum rod & bar (mechanical) and sheet/coil/plate (physical) typical datasheets; Poisson from MIL-HDBK-5J | Carpenter (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 7075-T6 stronger than Steel AISI 4340?
Steel AISI 4340 is stronger: its yield strength is 1,035 MPa against 503 MPa for Aluminum 7075-T6 (2.06x).
Which is lighter, Aluminum 7075-T6 or Steel AISI 4340?
Aluminum 7075-T6 is lighter: 2,800 kg/m³ against 7,840 kg/m³ for Steel AISI 4340.
Which is stiffer, Aluminum 7075-T6 or Steel AISI 4340?
Steel AISI 4340 is stiffer: Young's modulus 200 GPa against 71 GPa for Aluminum 7075-T6, so the same part in Steel AISI 4340 deflects less under the same load.
Which is lighter for the same job, Aluminum 7075-T6 or Steel AISI 4340?
For the same stiffness or strength: Aluminum 7075-T6 is lighter for a stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.
| Part that must be | Aluminum 7075-T6 | Steel AISI 4340 |
|---|---|---|
| Stiff rod or tie (tension) | about equal | about equal |
| Stiff beam (bending) | lighter | 1.67x heavier |
| Stiff panel or plate | lighter | 1.98x heavier |
| Strong rod or tie | lighter | 36% heavier |
| Strong beam | lighter | 1.73x heavier |
| Strong panel or plate | lighter | 1.95x 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 7075-T6 or Steel AISI 4340?
Aluminum 7075-T6 conducts heat better: 130 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 23.4 µm/m·K for Aluminum 7075-T6.