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EQ21A (EQ21A-T6, M18330) Magnesium

EQ21A magnesium is a magnesium alloy. It is typically furnished in the T6 temper. To achieve this temper, the metal is solution heat-treated and artificially aged until it meets standard mechanical property requirements. EQ21A is the ASTM designation for this material. M18330 is the UNS number.

It has the highest base cost among magnesium alloys. In addition, it has a moderately high density and a fairly high embodied energy.

The graph bars on the material properties cards below compare EQ21A magnesium to other magnesium alloys (top) and the entire database (bottom).

Mechanical Properties

Brinell Hardness


Compressive (Crushing) Strength

350 MPa 50 x 103 psi

Elastic (Young's, Tensile) Modulus

44 GPa 6.4 x 106 psi

Elongation at Break

2.4 %

Fatigue Strength

110 MPa 15 x 103 psi

Fracture Toughness

16 MPa-m1/2 14920 psi-in1/2

Poisson's Ratio


Shear Modulus

17 GPa 2.5 x 106 psi

Shear Strength

150 MPa 22 x 103 psi

Tensile Strength: Ultimate (UTS)

250 MPa 37 x 103 psi

Tensile Strength: Yield (Proof)

190 MPa 28 x 103 psi

Thermal Properties

Melting Completion (Liquidus)

640 °C 1180 °F

Melting Onset (Solidus)

560 °C 1040 °F

Solidification (Pattern Maker's) Shrinkage

1.3 %

Specific Heat Capacity

980 J/kg-K 0.23 BTU/lb-°F

Thermal Conductivity

110 W/m-K 65 BTU/h-ft-°F

Thermal Expansion

27 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

25 % IACS

Electrical Conductivity: Equal Weight (Specific)

120 % IACS

Otherwise Unclassified Properties

Base Metal Price

81 % relative


1.9 g/cm3 120 lb/ft3

Embodied Carbon

27 kg CO2/kg material

Embodied Energy

210 MJ/kg 89 x 103 BTU/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

5.6 MJ/m3

Resilience: Unit (Modulus of Resilience)

410 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

62 points

Strength to Weight: Axial

37 points

Strength to Weight: Bending

47 points

Thermal Diffusivity

61 m2/s

Thermal Shock Resistance

15 points

Alloy Composition

Magnesium (Mg) 93.8 to 96.8
Silver (Ag) 1.3 to 1.7
Zirconium (Zr) 0.4 to 1.0
Zinc (Zn) 0 to 0.2
Copper (Cu) 0.050 to 0.1
Manganese (Mn) 0 to 0.15
Silicon (Si) 0 to 0.010
Nickel (Ni) 0 to 0.010
Iron (Fe) 0 to 0.010
Unspecified Rare Earths 1.5 to 3.0
Residuals 0 to 0.3

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

Followup Questions

Similar Alloys

Further Reading

Magnesium Alloys Containing Rare Earth Metals: Structure and Properties, L.L. Rokhlin, 2003

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

ASTM B199: Standard Specification for Magnesium-Alloy Permanent Mold Castings

ASTM B403: Standard Specification for Magnesium-Alloy Investment Castings

ASTM B80: Standard Specification for Magnesium-Alloy Sand 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.

CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015