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7178 Aluminum vs. S81921 Stainless Steel

7178 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 7178 aluminum and the bottom bar is S81921 stainless steel.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 71
200
Elongation at Break, % 4.5 to 12
29
Fatigue Strength, MPa 120 to 210
370
Poisson's Ratio 0.32
0.28
Shear Modulus, GPa 27
79
Shear Strength, MPa 140 to 380
460
Tensile Strength: Ultimate (UTS), MPa 240 to 640
710
Tensile Strength: Yield (Proof), MPa 120 to 560
500

Thermal Properties

Latent Heat of Fusion, J/g 370
290
Maximum Temperature: Mechanical, °C 180
990
Melting Completion (Liquidus), °C 630
1430
Melting Onset (Solidus), °C 480
1390
Specific Heat Capacity, J/kg-K 860
480
Thermal Conductivity, W/m-K 130
15
Thermal Expansion, µm/m-K 23
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 31
2.2
Electrical Conductivity: Equal Weight (Specific), % IACS 91
2.5

Otherwise Unclassified Properties

Base Metal Price, % relative 10
14
Density, g/cm3 3.1
7.7
Embodied Carbon, kg CO2/kg material 8.2
2.9
Embodied Energy, MJ/kg 150
41
Embodied Water, L/kg 1110
150

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 24 to 52
180
Resilience: Unit (Modulus of Resilience), kJ/m3 110 to 2220
630
Stiffness to Weight: Axial, points 13
14
Stiffness to Weight: Bending, points 45
25
Strength to Weight: Axial, points 21 to 58
25
Strength to Weight: Bending, points 28 to 54
23
Thermal Diffusivity, mm2/s 47
4.0
Thermal Shock Resistance, points 10 to 28
20

Alloy Composition

Aluminum (Al), % 85.4 to 89.5
0
Carbon (C), % 0
0 to 0.030
Chromium (Cr), % 0.18 to 0.28
19 to 22
Copper (Cu), % 1.6 to 2.4
0
Iron (Fe), % 0 to 0.5
66.7 to 75.9
Magnesium (Mg), % 2.4 to 3.1
0
Manganese (Mn), % 0 to 0.3
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 0.4
0 to 1.0
Sulfur (S), % 0
0 to 0.030
Titanium (Ti), % 0 to 0.2
0
Zinc (Zn), % 6.3 to 7.3
0
Residuals, % 0 to 0.15
0