Materials / Compare
Aluminum vs. Steel
Compare Aluminum vs. Steel 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 | 276MPasourcetypical, 0.2% offset, .500 in dia specimen | 385MPasourcetypical: mean of 20,295 A992 flange mill-test coupons (1998 SSPC survey), as reported by AISC |
| Ultimate tensile strength | 310MPasourcetypical | 505MPasourcetypical: mean of 20,295 A992 flange mill-test coupons (1998 SSPC survey) |
| Elongation at break | 17%sourcetypical, in 4D, 0.500 in dia specimen | not sourced |
| Young's modulus (stiffness) | 68.3GPasourcetypical | 200GPasourcedesign value (AISC 360-16) |
| Density | 2,700kg/m³sourcenominal | 7,850kg/m³sourcenominal (constructional data) |
| Strength to weight | 102kN·m/kg2.08x higher | 49kN·m/kg |
| Stiffness to weight | 25.3MN·m/kg | 25.5MN·m/kg |
| Poisson's ratio | 0.33sourcetypical (handbook physical constant) | 0.3sourcedesign value (AISC 360-16 Commentary) |
| Shear modulus | 25.7GPa | 76.9GPa3x stiffer in shear |
| Bulk modulus | 67GPa | 167GPa |
| Speed of sound | 5,030m/s | 5,048m/s |
| Thermal | ||
| Thermal conductivity | 167W/m·Ksourcetypical, 20 °C | 48W/m·Ksourcenominal at 20 °C |
| Thermal expansion | 23.6µm/m·Ksourcetypical, mean 20-100 °C | 12µm/m·Ksourcenominal (constructional data, no temperature range stated) |
| 100 mm part over a 50 °C swing | 118µm growth | 60µm growth1.97x less |
| Specific heat | 896J/kg·Ksourcetypical, at 100 °C | 460–480J/kg·Ksourcebase material: EN S275JR unalloyed structural steel (the EN counterpart of A36), typical, 50/100 °C |
| Heats up and cools (diffusivity) | 69mm²/s5.31x faster | 13mm²/s |
| Thermal shock resistance | 19,159W/m3.55x more resistant | 5,390W/m |
| Melting point | 582–652°Csourcesolidus-liquidus | not sourced |
| Values for | 6061-T6/T651, Kaiser Aluminum typical properties (sheet, coil & plate datasheet); Poisson from MIL-HDBK-5J | Generic structural steel, cited as ASTM A992 (the current US structural grade): ASTM A992 W-shapes; Fy/Fu specified minimums from AISC publications (AISC 360-16 Commentary; Modern Steel Construction); elastic constants AISC 360; physical constants from the bauforumstahl structural-steel EPD, which names A992 among covered product standards. |
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 stronger than Steel?
Steel is stronger: its yield strength is 385 MPa against 276 MPa for Aluminum (39%).
Which is lighter, Aluminum or Steel?
Aluminum is lighter: 2,700 kg/m³ against 7,850 kg/m³ for Steel.
Which is stiffer, Aluminum or Steel?
Steel is stiffer: Young's modulus 200 GPa against 68.3 GPa for Aluminum, so the same part in Steel deflects less under the same load.
Which is lighter for the same job, Aluminum or Steel?
For the same stiffness or strength: Aluminum 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 | Steel |
|---|---|---|
| Stiff rod or tie (tension) | about equal | about equal |
| Stiff beam (bending) | lighter | 1.7x heavier |
| Stiff panel or plate | lighter | 2.03x heavier |
| Strong rod or tie | lighter | 2.08x heavier |
| Strong beam | lighter | 2.33x heavier |
| Strong panel or plate | lighter | 2.46x 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 or Steel?
Aluminum conducts heat better: 167 W/m·K against 48 W/m·K for Steel.
Which expands less with temperature?
Steel expands less: 12 µm/m·K against 23.6 µm/m·K for Aluminum.