SAE-AISI P21 Steel vs. 7178 Aluminum
SAE-AISI P21 steel belongs to the iron alloys classification, while 7178 aluminum belongs to the aluminum alloys. There are 23 material properties with values for both materials. Properties with values for just one material (8, in this case) are not shown. Please note that the two materials have significantly dissimilar densities. This means that additional care is required when interpreting the data, because some material properties are based on units of mass, while others are based on units of area or volume.
For each property being compared, the top bar is SAE-AISI P21 steel and the bottom bar is 7178 aluminum.
Metric UnitsUS Customary Units
Mechanical Properties
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 71 |
| Poisson's Ratio | 0.29 | |
| 0.32 |
| Shear Modulus, GPa | 73 | |
| 27 |
| Tensile Strength: Ultimate (UTS), MPa | 1130 | |
| 240 to 640 |
Thermal Properties
| Latent Heat of Fusion, J/g | 250 | |
| 370 |
| Melting Completion (Liquidus), °C | 1450 | |
| 630 |
| Melting Onset (Solidus), °C | 1410 | |
| 480 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 860 |
| Thermal Conductivity, W/m-K | 41 | |
| 130 |
| Thermal Expansion, µm/m-K | 12 | |
| 23 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.9 | |
| 31 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 9.0 | |
| 91 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 6.5 | |
| 10 |
| Density, g/cm3 | 7.9 | |
| 3.1 |
| Embodied Carbon, kg CO2/kg material | 2.3 | |
| 8.2 |
| Embodied Energy, MJ/kg | 32 | |
| 150 |
| Embodied Water, L/kg | 62 | |
| 1110 |
Common Calculations
| Stiffness to Weight: Axial, points | 13 | |
| 13 |
| Stiffness to Weight: Bending, points | 24 | |
| 45 |
| Strength to Weight: Axial, points | 40 | |
| 21 to 58 |
| Strength to Weight: Bending, points | 31 | |
| 28 to 54 |
| Thermal Diffusivity, mm2/s | 11 | |
| 47 |
| Thermal Shock Resistance, points | 37 | |
| 10 to 28 |
Alloy Composition
| Aluminum (Al), % | 0 | |
| 85.4 to 89.5 |
| Carbon (C), % | 0.18 to 0.22 | |
| 0 |
| Chromium (Cr), % | 0 to 0.5 | |
| 0.18 to 0.28 |
| Cobalt (Co), % | 1.1 to 1.3 | |
| 0 |
| Copper (Cu), % | 0 to 0.25 | |
| 1.6 to 2.4 |
| Iron (Fe), % | 92.1 to 94.2 | |
| 0 to 0.5 |
| Magnesium (Mg), % | 0 | |
| 2.4 to 3.1 |
| Manganese (Mn), % | 0.35 to 0.72 | |
| 0 to 0.3 |
| Nickel (Ni), % | 3.9 to 4.3 | |
| 0 |
| Phosphorus (P), % | 0 to 0.030 | |
| 0 |
| Silicon (Si), % | 0.2 to 0.4 | |
| 0 to 0.4 |
| Sulfur (S), % | 0 to 0.030 | |
| 0 |
| Titanium (Ti), % | 0 | |
| 0 to 0.2 |
| Vanadium (V), % | 0.15 to 0.25 | |
| 0 |
| Zinc (Zn), % | 0 | |
| 6.3 to 7.3 |
| Residuals, % | 0 | |
| 0 to 0.15 |