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7021 Aluminum vs. S81921 Stainless Steel

7021 aluminum belongs to the aluminum alloys classification, while S81921 stainless steel belongs to the iron 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 7021 aluminum and the bottom bar is S81921 stainless steel.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 69
200
Elongation at Break, % 9.4
29
Fatigue Strength, MPa 150
370
Poisson's Ratio 0.32
0.28
Shear Modulus, GPa 26
79
Shear Strength, MPa 270
460
Tensile Strength: Ultimate (UTS), MPa 460
710
Tensile Strength: Yield (Proof), MPa 390
500

Thermal Properties

Latent Heat of Fusion, J/g 380
290
Maximum Temperature: Mechanical, °C 200
990
Melting Completion (Liquidus), °C 630
1430
Melting Onset (Solidus), °C 510
1390
Specific Heat Capacity, J/kg-K 870
480
Thermal Conductivity, W/m-K 150
15
Thermal Expansion, µm/m-K 24
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 38
2.2
Electrical Conductivity: Equal Weight (Specific), % IACS 120
2.5

Otherwise Unclassified Properties

Base Metal Price, % relative 9.5
14
Density, g/cm3 2.9
7.7
Embodied Carbon, kg CO2/kg material 8.3
2.9
Embodied Energy, MJ/kg 150
41
Embodied Water, L/kg 1140
150

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 41
180
Resilience: Unit (Modulus of Resilience), kJ/m3 1110
630
Stiffness to Weight: Axial, points 13
14
Stiffness to Weight: Bending, points 47
25
Strength to Weight: Axial, points 44
25
Strength to Weight: Bending, points 45
23
Thermal Diffusivity, mm2/s 59
4.0
Thermal Shock Resistance, points 20
20

Alloy Composition

Aluminum (Al), % 90.7 to 93.7
0
Carbon (C), % 0
0 to 0.030
Chromium (Cr), % 0 to 0.050
19 to 22
Copper (Cu), % 0 to 0.25
0
Iron (Fe), % 0 to 0.4
66.7 to 75.9
Magnesium (Mg), % 1.2 to 1.8
0
Manganese (Mn), % 0 to 0.1
2.0 to 4.0
Molybdenum (Mo), % 0
1.0 to 2.0
Nickel (Ni), % 0
2.0 to 4.0
Nitrogen (N), % 0
0.14 to 0.2
Phosphorus (P), % 0
0 to 0.040
Silicon (Si), % 0 to 0.25
0 to 1.0
Sulfur (S), % 0
0 to 0.030
Titanium (Ti), % 0 to 0.1
0
Zinc (Zn), % 5.0 to 6.0
0
Zirconium (Zr), % 0.080 to 0.18
0
Residuals, % 0 to 0.15
0