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AZ91B Magnesium vs. SAE-AISI 8720 Steel

AZ91B magnesium belongs to the magnesium alloys classification, while SAE-AISI 8720 steel belongs to the iron alloys. There are 31 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 AZ91B magnesium and the bottom bar is SAE-AISI 8720 steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 63
150
Elastic (Young's, Tensile) Modulus, GPa 46
190
Elongation at Break, % 5.0
25
Fatigue Strength, MPa 79
240
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 18
73
Shear Strength, MPa 140
320
Tensile Strength: Ultimate (UTS), MPa 240
500
Tensile Strength: Yield (Proof), MPa 160
330

Thermal Properties

Latent Heat of Fusion, J/g 360
250
Maximum Temperature: Mechanical, °C 130
410
Melting Completion (Liquidus), °C 600
1460
Melting Onset (Solidus), °C 470
1420
Specific Heat Capacity, J/kg-K 990
470
Thermal Conductivity, W/m-K 73
39
Thermal Expansion, µm/m-K 26
11

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 11
7.3
Electrical Conductivity: Equal Weight (Specific), % IACS 58
8.3

Otherwise Unclassified Properties

Base Metal Price, % relative 12
2.6
Density, g/cm3 1.7
7.8
Embodied Carbon, kg CO2/kg material 22
1.5
Embodied Energy, MJ/kg 160
20
Embodied Water, L/kg 990
50

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 11
110
Resilience: Unit (Modulus of Resilience), kJ/m3 280
290
Stiffness to Weight: Axial, points 15
13
Stiffness to Weight: Bending, points 69
24
Strength to Weight: Axial, points 38
18
Strength to Weight: Bending, points 49
18
Thermal Diffusivity, mm2/s 42
10
Thermal Shock Resistance, points 14
17

Alloy Composition

Aluminum (Al), % 8.3 to 9.7
0
Carbon (C), % 0
0.18 to 0.23
Chromium (Cr), % 0
0.4 to 0.6
Copper (Cu), % 0 to 0.35
0
Iron (Fe), % 0
96.8 to 98
Magnesium (Mg), % 87.9 to 91.2
0
Manganese (Mn), % 0.13 to 0.5
0.7 to 0.9
Molybdenum (Mo), % 0
0.2 to 0.3
Nickel (Ni), % 0 to 0.030
0.4 to 0.7
Phosphorus (P), % 0
0 to 0.035
Silicon (Si), % 0 to 0.5
0.15 to 0.35
Sulfur (S), % 0
0 to 0.040
Zinc (Zn), % 0.35 to 1.0
0