# AZ81A-T4 Magnesium

AZ81A-T4 magnesium is AZ81A magnesium in the T4 temper. To achieve this temper, the metal is solution heat-treated and naturally aged. The graph bars on the material properties cards below compare AZ81A-T4 magnesium to other magnesium alloys (top) and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

## Mechanical Properties

Brinell Hardness

55

Compressive (Crushing) Strength

370 *MPa* 54 *x 10 ^{3} psi*

Elastic (Young's, Tensile) Modulus

46 *GPa* 6.6 *x 10 ^{6} psi*

Elongation at Break

8.8 *%*

Fatigue Strength

78 *MPa* 11 *x 10 ^{3} psi*

Poisson's Ratio

0.29

Shear Modulus

18 *GPa* 2.6 *x 10 ^{6} psi*

Shear Strength

130 *MPa* 19 *x 10 ^{3} psi*

Tensile Strength: Ultimate (UTS)

240 *MPa* 35 *x 10 ^{3} psi*

Tensile Strength: Yield (Proof)

84 *MPa* 12 *x 10 ^{3} psi*

## Thermal Properties

Latent Heat of Fusion

350 *J/g*

Maximum Temperature: Mechanical

130 *°C* 260 *°F*

Melting Completion (Liquidus)

600 *°C* 1120 *°F*

Melting Onset (Solidus)

500 *°C* 940 *°F*

Solidification (Pattern Maker's) Shrinkage

1.3 *%*

Specific Heat Capacity

990 *J/kg-K* 0.24 *BTU/lb-°F*

Thermal Conductivity

84 *W/m-K* 49 *BTU/h-ft-°F*

Thermal Expansion

27 *µm/m-K*

## Electrical Properties

Electrical Conductivity: Equal Volume

12 *% IACS*

Electrical Conductivity: Equal Weight (Specific)

65 *% IACS*

## Otherwise Unclassified Properties

Base Metal Price

12 *% relative*

Density

1.7 *g/cm ^{3}* 110

*lb/ft*

^{3}Embodied Carbon

23 *kg CO _{2}/kg material*

Embodied Energy

160 *MJ/kg* 67 *x 10 ^{3} BTU/lb*

Embodied Water

990 *L/kg* 120 *gal/lb*

## Common Calculations

Resilience: Ultimate (Unit Rupture Work)

17 *MJ/m ^{3}*

Resilience: Unit (Modulus of Resilience)

78 *kJ/m ^{3}*

Stiffness to Weight: Axial

15 *points*

Stiffness to Weight: Bending

70 *points*

Strength to Weight: Axial

39 *points*

Strength to Weight: Bending

50 *points*

Thermal Diffusivity

50 *mm ^{2}/s*

Thermal Shock Resistance

14 *points*

## Alloy Composition

Mg | 89.8 to 92.5 | |

Al | 7.0 to 8.1 | |

Zn | 0.4 to 1.0 | |

Mn | 0.13 to 0.35 | |

Si | 0 to 0.3 | |

Cu | 0 to 0.1 | |

Ni | 0 to 0.010 | |

res. | 0 to 0.3 |

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

## Followup Questions

## Further Reading

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

ASTM B403: Standard Specification for Magnesium-Alloy Investment Castings

Welding and Joining of Magnesium Alloys, Liming Liu (editor), 2010

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.

Advanced Materials in Automotive Engineering, Jason Rowe (editor), 2012

Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, ASM Handbook vol. 2, ASM International, 1993