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S21900 Stainless Steel vs. 7178 Aluminum

S21900 stainless 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 (4, 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 S21900 stainless steel and the bottom bar is 7178 aluminum.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 200
71
Elongation at Break, % 50
4.5 to 12
Fatigue Strength, MPa 380
120 to 210
Poisson's Ratio 0.28
0.32
Shear Modulus, GPa 78
27
Shear Strength, MPa 510
140 to 380
Tensile Strength: Ultimate (UTS), MPa 710
240 to 640
Tensile Strength: Yield (Proof), MPa 390
120 to 560

Thermal Properties

Latent Heat of Fusion, J/g 290
370
Maximum Temperature: Mechanical, °C 980
180
Melting Completion (Liquidus), °C 1400
630
Melting Onset (Solidus), °C 1350
480
Specific Heat Capacity, J/kg-K 480
860
Thermal Conductivity, W/m-K 14
130
Thermal Expansion, µm/m-K 17
23

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 2.5
31
Electrical Conductivity: Equal Weight (Specific), % IACS 2.9
91

Otherwise Unclassified Properties

Base Metal Price, % relative 15
10
Density, g/cm3 7.7
3.1
Embodied Carbon, kg CO2/kg material 3.0
8.2
Embodied Energy, MJ/kg 43
150
Embodied Water, L/kg 160
1110

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 300
24 to 52
Resilience: Unit (Modulus of Resilience), kJ/m3 380
110 to 2220
Stiffness to Weight: Axial, points 14
13
Stiffness to Weight: Bending, points 25
45
Strength to Weight: Axial, points 26
21 to 58
Strength to Weight: Bending, points 23
28 to 54
Thermal Diffusivity, mm2/s 3.8
47
Thermal Shock Resistance, points 15
10 to 28

Alloy Composition

Aluminum (Al), % 0
85.4 to 89.5
Carbon (C), % 0 to 0.080
0
Chromium (Cr), % 19 to 21.5
0.18 to 0.28
Copper (Cu), % 0
1.6 to 2.4
Iron (Fe), % 59.4 to 67.4
0 to 0.5
Magnesium (Mg), % 0
2.4 to 3.1
Manganese (Mn), % 8.0 to 10
0 to 0.3
Nickel (Ni), % 5.5 to 7.5
0
Nitrogen (N), % 0.15 to 0.4
0
Phosphorus (P), % 0 to 0.045
0
Silicon (Si), % 0 to 1.0
0 to 0.4
Sulfur (S), % 0 to 0.030
0
Titanium (Ti), % 0
0 to 0.2
Zinc (Zn), % 0
6.3 to 7.3
Residuals, % 0
0 to 0.15