ASTM A387 Grade 21 Steel vs. 7178 Aluminum
ASTM A387 grade 21 steel belongs to the iron alloys classification, while 7178 aluminum belongs to the aluminum alloys. There are 30 material properties with values for both materials. Properties with values for just one material (2, 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 ASTM A387 grade 21 steel and the bottom bar is 7178 aluminum.
Metric UnitsUS Customary Units
Mechanical Properties
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 71 |
| Elongation at Break, % | 21 | |
| 4.5 to 12 |
| Fatigue Strength, MPa | 160 to 250 | |
| 120 to 210 |
| Poisson's Ratio | 0.29 | |
| 0.32 |
| Shear Modulus, GPa | 74 | |
| 27 |
| Shear Strength, MPa | 310 to 370 | |
| 140 to 380 |
| Tensile Strength: Ultimate (UTS), MPa | 500 to 590 | |
| 240 to 640 |
| Tensile Strength: Yield (Proof), MPa | 230 to 350 | |
| 120 to 560 |
Thermal Properties
| Latent Heat of Fusion, J/g | 260 | |
| 370 |
| Maximum Temperature: Mechanical, °C | 480 | |
| 180 |
| Melting Completion (Liquidus), °C | 1470 | |
| 630 |
| Melting Onset (Solidus), °C | 1430 | |
| 480 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 860 |
| Thermal Conductivity, W/m-K | 41 | |
| 130 |
| Thermal Expansion, µm/m-K | 13 | |
| 23 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.6 | |
| 31 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 8.8 | |
| 91 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 4.1 | |
| 10 |
| Density, g/cm3 | 7.9 | |
| 3.1 |
| Embodied Carbon, kg CO2/kg material | 1.8 | |
| 8.2 |
| Embodied Energy, MJ/kg | 23 | |
| 150 |
| Embodied Water, L/kg | 62 | |
| 1110 |
Common Calculations
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 84 to 110 | |
| 24 to 52 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 140 to 320 | |
| 110 to 2220 |
| Stiffness to Weight: Axial, points | 13 | |
| 13 |
| Stiffness to Weight: Bending, points | 24 | |
| 45 |
| Strength to Weight: Axial, points | 18 to 21 | |
| 21 to 58 |
| Strength to Weight: Bending, points | 18 to 20 | |
| 28 to 54 |
| Thermal Diffusivity, mm2/s | 11 | |
| 47 |
| Thermal Shock Resistance, points | 14 to 17 | |
| 10 to 28 |
Alloy Composition
| Aluminum (Al), % | 0 | |
| 85.4 to 89.5 |
| Carbon (C), % | 0.050 to 0.15 | |
| 0 |
| Chromium (Cr), % | 2.8 to 3.3 | |
| 0.18 to 0.28 |
| Copper (Cu), % | 0 | |
| 1.6 to 2.4 |
| Iron (Fe), % | 94.4 to 96 | |
| 0 to 0.5 |
| Magnesium (Mg), % | 0 | |
| 2.4 to 3.1 |
| Manganese (Mn), % | 0.3 to 0.6 | |
| 0 to 0.3 |
| Molybdenum (Mo), % | 0.9 to 1.1 | |
| 0 |
| Phosphorus (P), % | 0 to 0.025 | |
| 0 |
| Silicon (Si), % | 0 to 0.5 | |
| 0 to 0.4 |
| Sulfur (S), % | 0 to 0.025 | |
| 0 |
| Titanium (Ti), % | 0 | |
| 0 to 0.2 |
| Zinc (Zn), % | 0 | |
| 6.3 to 7.3 |
| Residuals, % | 0 | |
| 0 to 0.15 |