Materials / Compare
Aluminum vs. Iron
Compare Aluminum vs. Iron 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 | 186MPasourcetypical (0.2% YS), hot rolled + SRA/recrystallization anneal |
| Ultimate tensile strength | 310MPasourcetypical | 290MPasourcetypical, SRA/recrystallization anneal |
| Elongation at break | 17%sourcetypical, in 4D, 0.500 in dia specimen | 38%sourcetypical, gauge 4D0 |
| Young's modulus (stiffness) | 68.3GPasourcetypical | 207GPasourcetypical, after SRA/recrystallization anneal |
| Density | 2,700kg/m³sourcenominal | 7,860kg/m³sourcetypical |
| Strength to weight | 102kN·m/kg4.32x higher | 23.7kN·m/kg |
| Stiffness to weight | 25.3MN·m/kg | 26.3MN·m/kg4% higher |
| Poisson's ratio | 0.33sourcetypical (handbook physical constant) | 0.282sourceNIST critically evaluated best value (polycrystalline iron) |
| Shear modulus | 25.7GPa | 80.7GPa3.14x stiffer in shear |
| Bulk modulus | 67GPa | 158GPa |
| Speed of sound | 5,030m/s | 5,132m/s |
| Thermal | ||
| Thermal conductivity | 167W/m·Ksourcetypical, 20 °C | 73.2W/m·Ksourcetypical at 20 °C |
| Thermal expansion | 23.6µm/m·Ksourcetypical, mean 20-100 °C | 13.7µm/m·Ksourcemean, 20-399 °C |
| 100 mm part over a 50 °C swing | 118µm growth | 68.5µm growth1.72x less |
| Specific heat | 896J/kg·Ksourcetypical, at 100 °C | 450J/kg·Ksourcetypical |
| Heats up and cools (diffusivity) | 69mm²/s3.34x faster | 20.7mm²/s |
| Thermal shock resistance | 19,159W/m5.56x more resistant | 3,447W/m |
| Melting point | 582–652°Csourcesolidus-liquidus | 1,532°Csourcetypical |
| Values for | 6061-T6/T651, Kaiser Aluminum typical properties (sheet, coil & plate datasheet); Poisson from MIL-HDBK-5J | Cleveland-Cliffs / AK Steel ARMCO Pure Iron Product Data Bulletin (07/2022): Table 1 typical physical properties, Table 2 typical mechanical properties after SRA/recrystallization anneal. |
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 Iron?
Aluminum is stronger: its yield strength is 276 MPa against 186 MPa for Iron (48%).
Which is lighter, Aluminum or Iron?
Aluminum is lighter: 2,700 kg/m³ against 7,860 kg/m³ for Iron.
Which is stiffer, Aluminum or Iron?
Iron is stiffer: Young's modulus 207 GPa against 68.3 GPa for Aluminum, so the same part in Iron deflects less under the same load.
Which is lighter for the same job, Aluminum or Iron?
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; Iron is lighter for a stiff rod or tie (tension).
| Part that must be | Aluminum | Iron |
|---|---|---|
| Stiff rod or tie (tension) | 4% heavier | lighter |
| Stiff beam (bending) | lighter | 1.67x heavier |
| Stiff panel or plate | lighter | 2.01x heavier |
| Strong rod or tie | lighter | 4.32x heavier |
| Strong beam | lighter | 3.79x heavier |
| Strong panel or plate | lighter | 3.55x 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 Iron?
Aluminum conducts heat better: 167 W/m·K against 73.2 W/m·K for Iron.
Which expands less with temperature?
Iron expands less: 13.7 µm/m·K against 23.6 µm/m·K for Aluminum.