SAE-AISI 81B45 Steel vs. 2218 Aluminum
SAE-AISI 81B45 steel belongs to the iron alloys classification, while 2218 aluminum belongs to the aluminum alloys. 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 81B45 steel and the bottom bar is 2218 aluminum.
Metric UnitsUS Customary Units
Mechanical Properties
| Brinell Hardness | 160 to 200 | |
| 95 to 110 |
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 73 |
| Elongation at Break, % | 12 to 24 | |
| 6.8 to 10 |
| Fatigue Strength, MPa | 250 to 350 | |
| 110 |
| Poisson's Ratio | 0.29 | |
| 0.33 |
| Shear Modulus, GPa | 73 | |
| 27 |
| Shear Strength, MPa | 340 to 400 | |
| 210 to 250 |
| Tensile Strength: Ultimate (UTS), MPa | 540 to 670 | |
| 330 to 430 |
| Tensile Strength: Yield (Proof), MPa | 350 to 560 | |
| 260 to 310 |
Thermal Properties
| Latent Heat of Fusion, J/g | 250 | |
| 390 |
| Maximum Temperature: Mechanical, °C | 410 | |
| 220 |
| Melting Completion (Liquidus), °C | 1460 | |
| 640 |
| Melting Onset (Solidus), °C | 1420 | |
| 510 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 870 |
| Thermal Conductivity, W/m-K | 40 | |
| 140 |
| Thermal Expansion, µm/m-K | 12 | |
| 22 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.2 | |
| 37 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 8.3 | |
| 110 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 2.3 | |
| 11 |
| Density, g/cm3 | 7.8 | |
| 3.1 |
| Embodied Carbon, kg CO2/kg material | 1.5 | |
| 8.2 |
| Embodied Energy, MJ/kg | 20 | |
| 150 |
| Embodied Water, L/kg | 49 | |
| 1130 |
Common Calculations
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 77 to 110 | |
| 27 to 31 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 320 to 840 | |
| 450 to 650 |
| Stiffness to Weight: Axial, points | 13 | |
| 13 |
| Stiffness to Weight: Bending, points | 24 | |
| 45 |
| Strength to Weight: Axial, points | 19 to 24 | |
| 30 to 39 |
| Strength to Weight: Bending, points | 19 to 22 | |
| 34 to 41 |
| Thermal Diffusivity, mm2/s | 11 | |
| 52 |
| Thermal Shock Resistance, points | 17 to 21 | |
| 15 to 19 |
Alloy Composition
| Aluminum (Al), % | 0 | |
| 88.8 to 93.6 |
| Boron (B), % | 0.00050 to 0.0030 | |
| 0 |
| Carbon (C), % | 0.43 to 0.48 | |
| 0 |
| Chromium (Cr), % | 0.35 to 0.55 | |
| 0 to 0.1 |
| Copper (Cu), % | 0 | |
| 3.5 to 4.5 |
| Iron (Fe), % | 97 to 98 | |
| 0 to 1.0 |
| Magnesium (Mg), % | 0 | |
| 1.2 to 1.8 |
| Manganese (Mn), % | 0.75 to 1.0 | |
| 0 to 0.2 |
| Molybdenum (Mo), % | 0.080 to 0.15 | |
| 0 |
| Nickel (Ni), % | 0.2 to 0.4 | |
| 1.7 to 2.3 |
| Phosphorus (P), % | 0 to 0.035 | |
| 0 |
| Silicon (Si), % | 0.15 to 0.35 | |
| 0 to 0.9 |
| Sulfur (S), % | 0 to 0.040 | |
| 0 |
| Zinc (Zn), % | 0 | |
| 0 to 0.25 |
| Residuals, % | 0 | |
| 0 to 0.15 |