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S21904 Stainless Steel vs. 7021 Aluminum

S21904 stainless steel belongs to the iron alloys classification, while 7021 aluminum belongs to the aluminum alloys. There are 30 material properties with values for both materials. Properties with values for just one material (3, 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 S21904 stainless steel and the bottom bar is 7021 aluminum.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 200
69
Elongation at Break, % 17 to 51
9.4
Fatigue Strength, MPa 380 to 550
150
Poisson's Ratio 0.28
0.32
Shear Modulus, GPa 78
26
Shear Strength, MPa 510 to 620
270
Tensile Strength: Ultimate (UTS), MPa 700 to 1000
460
Tensile Strength: Yield (Proof), MPa 390 to 910
390

Thermal Properties

Latent Heat of Fusion, J/g 290
380
Maximum Temperature: Mechanical, °C 980
200
Melting Completion (Liquidus), °C 1400
630
Melting Onset (Solidus), °C 1350
510
Specific Heat Capacity, J/kg-K 480
870
Thermal Conductivity, W/m-K 14
150
Thermal Expansion, µm/m-K 17
24

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 2.5
38
Electrical Conductivity: Equal Weight (Specific), % IACS 2.9
120

Otherwise Unclassified Properties

Base Metal Price, % relative 15
9.5
Density, g/cm3 7.7
2.9
Embodied Carbon, kg CO2/kg material 3.0
8.3
Embodied Energy, MJ/kg 43
150
Embodied Water, L/kg 160
1140

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 160 to 310
41
Resilience: Unit (Modulus of Resilience), kJ/m3 380 to 2070
1110
Stiffness to Weight: Axial, points 14
13
Stiffness to Weight: Bending, points 25
47
Strength to Weight: Axial, points 25 to 36
44
Strength to Weight: Bending, points 23 to 29
45
Thermal Diffusivity, mm2/s 3.8
59
Thermal Shock Resistance, points 15 to 21
20

Alloy Composition

Aluminum (Al), % 0
90.7 to 93.7
Carbon (C), % 0 to 0.040
0
Chromium (Cr), % 19 to 21.5
0 to 0.050
Copper (Cu), % 0
0 to 0.25
Iron (Fe), % 59.5 to 67.4
0 to 0.4
Magnesium (Mg), % 0
1.2 to 1.8
Manganese (Mn), % 8.0 to 10
0 to 0.1
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 0.25
Sulfur (S), % 0 to 0.030
0
Titanium (Ti), % 0
0 to 0.1
Zinc (Zn), % 0
5.0 to 6.0
Zirconium (Zr), % 0
0.080 to 0.18
Residuals, % 0
0 to 0.15