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AZ91B (AZ91B-F, M11912) Magnesium

AZ91B magnesium is a magnesium alloy. It is typically furnished in the as-fabricated (no temper or treatment) condition. AZ91B is the ASTM designation for this material. M11912 is the UNS number. It has a moderately low melting temperature relative to other magnesium alloys in the database. The graph bars on the material properties cards below compare AZ91B magnesium to other magnesium alloys (top) and the entire database (bottom).

Mechanical Properties

Brinell Hardness


Compressive (Crushing) Strength

160 MPa 23 x 103 psi

Elastic (Young's, Tensile) Modulus

46 GPa 6.7 x 106 psi

Elongation at Break

5.0 %

Fatigue Strength

79 MPa 11 x 103 psi

Poisson's Ratio


Rockwell F Hardness


Shear Modulus

18 GPa 2.6 x 106 psi

Shear Strength

140 MPa 20 x 103 psi

Tensile Strength: Ultimate (UTS)

240 MPa 35 x 103 psi

Tensile Strength: Yield (Proof)

160 MPa 23 x 103 psi

Thermal Properties

Melting Completion (Liquidus)

600 °C 1100 °F

Melting Onset (Solidus)

470 °C 880 °F

Specific Heat Capacity

990 J/kg-K 0.24 BTU/lb-°F

Thermal Conductivity

73 W/m-K 42 BTU/h-ft-°F

Thermal Expansion

26 µm/m-K

Otherwise Unclassified Properties

Base Metal Price

12 % relative


1.7 g/cm3 110 lb/ft3

Embodied Carbon

22 kg CO2/kg material

Embodied Energy

160 MJ/kg 67 x 103 BTU/lb

Embodied Water

990 L/kg 120 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

11 MJ/m3

Resilience: Unit (Modulus of Resilience)

280 kJ/m3

Stiffness to Weight: Axial

15 points

Stiffness to Weight: Bending

69 points

Strength to Weight: Axial

38 points

Strength to Weight: Bending

49 points

Thermal Diffusivity

42 m2/s

Thermal Shock Resistance

14 points

Alloy Composition

Magnesium (Mg) 87.8 to 91.6
Aluminum (Al) 8.0 to 10
Zinc (Zn) 0.3 to 1.0
Manganese (Mn) 0.1 to 0.6
Silicon (Si) 0 to 0.5
Copper (Cu) 0 to 0.35
Nickel (Ni) 0 to 0.030
Iron (Fe) 0 to 0.030
Residuals 0 to 0.050

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ASTM B94: Standard Specification for Magnesium-Alloy Die Castings

ISO 16220: Magnesium and magnesium alloys - Magnesium alloy ingots and castings

Essential Readings in Magnesium Technology, Suveen N. Mathaudhu et al. (editors), 2014

Environmental Degradation of Advanced and Traditional Engineering Materials, Lloyd H. Hihara et al., 2014.