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AZ91B Magnesium vs. R31538 Cobalt

AZ91B magnesium belongs to the magnesium alloys classification, while R31538 cobalt belongs to the cobalt alloys. There are 27 material properties with values for both materials. Properties with values for just one material (8, 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 R31538 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 46
220
Elongation at Break, % 5.0
13 to 23
Fatigue Strength, MPa 79
310 to 480
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 18
86
Tensile Strength: Ultimate (UTS), MPa 240
1020 to 1360
Tensile Strength: Yield (Proof), MPa 160
580 to 930

Thermal Properties

Latent Heat of Fusion, J/g 360
320
Melting Completion (Liquidus), °C 600
1360
Melting Onset (Solidus), °C 470
1290
Specific Heat Capacity, J/kg-K 990
450
Thermal Conductivity, W/m-K 73
13
Thermal Expansion, µm/m-K 26
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 11
2.0
Electrical Conductivity: Equal Weight (Specific), % IACS 58
2.1

Otherwise Unclassified Properties

Density, g/cm3 1.7
8.4
Embodied Carbon, kg CO2/kg material 22
8.1
Embodied Energy, MJ/kg 160
110
Embodied Water, L/kg 990
530

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 11
140 to 200
Resilience: Unit (Modulus of Resilience), kJ/m3 280
750 to 1920
Stiffness to Weight: Axial, points 15
15
Stiffness to Weight: Bending, points 69
24
Strength to Weight: Axial, points 38
34 to 45
Strength to Weight: Bending, points 49
27 to 32
Thermal Diffusivity, mm2/s 42
3.5
Thermal Shock Resistance, points 14
25 to 33

Alloy Composition

Aluminum (Al), % 8.3 to 9.7
0
Carbon (C), % 0
0.15 to 0.35
Chromium (Cr), % 0
26 to 30
Cobalt (Co), % 0
58.7 to 68.9
Copper (Cu), % 0 to 0.35
0
Iron (Fe), % 0
0 to 0.75
Magnesium (Mg), % 87.9 to 91.2
0
Manganese (Mn), % 0.13 to 0.5
0 to 1.0
Molybdenum (Mo), % 0
5.0 to 7.0
Nickel (Ni), % 0 to 0.030
0 to 1.0
Nitrogen (N), % 0
0 to 0.25
Silicon (Si), % 0 to 0.5
0 to 1.0
Zinc (Zn), % 0.35 to 1.0
0