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7129 Aluminum vs. ASTM A387 Grade 21 Steel

7129 Aluminum belongs to the aluminum alloys classification, while ASTM A387 grade 21 steel belongs to the iron alloys. There are 30 material properties with values for both materials. Properties with values for just one material (2, 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 7129 Aluminum and the bottom bar is ASTM A387 grade 21 steel.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 69
190
Elongation at Break, % 9.0 to 9.1
21
Fatigue Strength, MPa 150 to 190
160 to 250
Poisson's Ratio 0.33
0.29
Shear Modulus, GPa 26
74
Shear Strength, MPa 250 to 260
310 to 370
Tensile Strength: Ultimate (UTS), MPa 430
500 to 590
Tensile Strength: Yield (Proof), MPa 380 to 390
230 to 350

Thermal Properties

Latent Heat of Fusion, J/g 380
260
Maximum Temperature: Mechanical, °C 180
480
Melting Completion (Liquidus), °C 630
1470
Melting Onset (Solidus), °C 510
1430
Specific Heat Capacity, J/kg-K 880
470
Thermal Conductivity, W/m-K 150
41
Thermal Expansion, µm/m-K 24
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 40
7.6
Electrical Conductivity: Equal Weight (Specific), % IACS 120
8.8

Otherwise Unclassified Properties

Base Metal Price, % relative 9.5
4.1
Density, g/cm3 2.9
7.9
Embodied Carbon, kg CO2/kg material 8.3
1.8
Embodied Energy, MJ/kg 150
23
Embodied Water, L/kg 1150
62

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 37 to 38
84 to 110
Resilience: Unit (Modulus of Resilience), kJ/m3 1050 to 1090
140 to 320
Stiffness to Weight: Axial, points 13
13
Stiffness to Weight: Bending, points 47
24
Strength to Weight: Axial, points 41
18 to 21
Strength to Weight: Bending, points 43 to 44
18 to 20
Thermal Diffusivity, mm2/s 58
11
Thermal Shock Resistance, points 19
14 to 17

Alloy Composition

Aluminum (Al), % 91 to 94
0
Carbon (C), % 0
0.050 to 0.15
Chromium (Cr), % 0 to 0.1
2.8 to 3.3
Copper (Cu), % 0.5 to 0.9
0
Gallium (Ga), % 0 to 0.030
0
Iron (Fe), % 0 to 0.3
94.4 to 96
Magnesium (Mg), % 1.3 to 2.0
0
Manganese (Mn), % 0 to 0.1
0.3 to 0.6
Molybdenum (Mo), % 0
0.9 to 1.1
Phosphorus (P), % 0
0 to 0.025
Silicon (Si), % 0 to 0.15
0 to 0.5
Sulfur (S), % 0
0 to 0.025
Titanium (Ti), % 0 to 0.050
0
Vanadium (V), % 0 to 0.050
0
Zinc (Zn), % 4.2 to 5.2
0
Residuals, % 0 to 0.15
0