SAE-AISI 8645 Steel vs. 2018 Aluminum
SAE-AISI 8645 steel belongs to the iron alloys classification, while 2018 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 8645 steel and the bottom bar is 2018 aluminum.
Metric UnitsUS Customary Units
Mechanical Properties
| Brinell Hardness | 180 to 200 | |
| 120 |
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 73 |
| Elongation at Break, % | 12 to 23 | |
| 9.6 |
| Fatigue Strength, MPa | 280 to 350 | |
| 120 |
| Poisson's Ratio | 0.29 | |
| 0.33 |
| Shear Modulus, GPa | 73 | |
| 27 |
| Shear Strength, MPa | 380 to 400 | |
| 270 |
| Tensile Strength: Ultimate (UTS), MPa | 600 to 670 | |
| 420 |
| Tensile Strength: Yield (Proof), MPa | 390 to 560 | |
| 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 | 39 | |
| 150 |
| Thermal Expansion, µm/m-K | 13 | |
| 22 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.3 | |
| 40 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 8.4 | |
| 120 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 2.6 | |
| 11 |
| Density, g/cm3 | 7.8 | |
| 3.1 |
| Embodied Carbon, kg CO2/kg material | 1.5 | |
| 8.1 |
| Embodied Energy, MJ/kg | 20 | |
| 150 |
| Embodied Water, L/kg | 50 | |
| 1130 |
Common Calculations
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 77 to 120 | |
| 37 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 420 to 840 | |
| 670 |
| Stiffness to Weight: Axial, points | 13 | |
| 13 |
| Stiffness to Weight: Bending, points | 24 | |
| 45 |
| Strength to Weight: Axial, points | 21 to 24 | |
| 38 |
| Strength to Weight: Bending, points | 20 to 22 | |
| 41 |
| Thermal Diffusivity, mm2/s | 10 | |
| 57 |
| Thermal Shock Resistance, points | 18 to 20 | |
| 19 |
Alloy Composition
| Aluminum (Al), % | 0 | |
| 89.7 to 94.4 |
| Carbon (C), % | 0.43 to 0.48 | |
| 0 |
| Chromium (Cr), % | 0.4 to 0.6 | |
| 0 to 0.1 |
| Copper (Cu), % | 0 | |
| 3.5 to 4.5 |
| Iron (Fe), % | 96.5 to 97.7 | |
| 0 to 1.0 |
| Magnesium (Mg), % | 0 | |
| 0.45 to 0.9 |
| Manganese (Mn), % | 0.75 to 1.0 | |
| 0 to 0.2 |
| Molybdenum (Mo), % | 0.15 to 0.25 | |
| 0 |
| Nickel (Ni), % | 0.4 to 0.7 | |
| 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 |