Magnesium AZ31B-H24 vs. Magnesium AZ91D

Compare Magnesium AZ31B-H24 vs. Magnesium AZ91D strength, stiffness, weight and thermal properties.

Mechanical	Magnesium AZ31B-H24	Magnesium AZ91D
Yield strength	220MPa147% stronger	150MPa2
Ultimate tensile strength	290MPa126% stronger	230MPa2
Elongation at break	13%14.33x more ductile	3%2
Young's modulus (stiffness)	44.8GPa3	45GPa2
Density	1,769kg/m³3	1,810kg/m³2
Strength to weight	124kN·m/kg1.5x higher	82.9kN·m/kg
Stiffness to weight	25.3MN·m/kg2% higher	24.9MN·m/kg
Poisson's ratio	0.353	base material0.353
Shear modulus	16.6GPa	16.7GPa
Bulk modulus	49.8GPa	50GPa
Speed of sound	5,032m/s	4,986m/s

Stiffness against densityHigher and further left: stiffer for its weight

Strength against densityHigher and further left: stronger for its weight

Thermal	Magnesium AZ31B-H24	Magnesium AZ91D
Thermal conductivity	76.9W/m·K1	72W/m·K2
Thermal expansion	26.8µm/m·K1	25µm/m·K2
100 mm part over a 50 °C swing	134µm growth	125µm growth7% less
Specific heat	1,040J/kg·K1	1,050J/kg·K2
Heats up and cools (diffusivity)	41.8mm²/s10% faster	37.9mm²/s
Thermal shock resistance	9,159W/m47% more resistant	6,240W/m
Melting point	not sourced	melting range470–595°C2
Max service temperature	149°C3	not sourced

Thermal conductivity against densityHigher and further left: spreads more heat for its weight

Thermal expansion against thermal conductivityLower and further right: warps less when heated

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Sources3 documents: Magnesium Elektron, U.S. Department of Defense

Magnesium AZ31B-H24: AZ31B-H24 sheet 0.016-0.062 in., MIL-HDBK-5J Table 4.2.1.0(b) (AMS 4377); strengths are S-basis MINIMUMS
Magnesium AZ91D: ELEKTRON AZ91D magnesium die-casting alloy, as cast; Magnesium Elektron datasheet 475 (7/01), typical properties; Poisson from MIL-HDBK-5J for AZ91C castings.

1
Elektron AZ31B Sheet, Plate & Coil (Datasheet 482)Magnesium Elektronarchived copyMagnesium AZ31B-H24 · Yield strength: typical, H24, 0.5-6 mm, 0.2 % proof stressMagnesium AZ31B-H24 · Ultimate tensile strength: typical, H24, 0.5-6 mmMagnesium AZ31B-H24 · Elongation at break: typical, H24, 0.5-6 mm, gauge 5.65√AMagnesium AZ31B-H24 · Thermal conductivity: typical (temper/temperature not stated)Magnesium AZ31B-H24 · Thermal expansion: typical (temperature range not stated)Magnesium AZ31B-H24 · Specific heat: typical
2
Elektron Die Casting Alloys (Datasheet 475)Magnesium Elektronarchived copyMagnesium AZ91D · Yield strength: typical, 0.2% tensile yield, ambient temperatureMagnesium AZ91D · Ultimate tensile strength: typical, ambient temperatureMagnesium AZ91D · Elongation at break: typical, ambient temperatureMagnesium AZ91D · Young's modulus (stiffness): typicalMagnesium AZ91D · Density: typicalMagnesium AZ91D · Thermal conductivity: typicalMagnesium AZ91D · Thermal expansion: typical, temperature range not statedMagnesium AZ91D · Specific heat: typicalMagnesium AZ91D · Melting point: melting range
3
MIL-HDBK-5J, Metallic Materials and Elements for Aerospace Vehicle Structures (2003)U.S. Department of DefenseMagnesium AZ31B-H24 · Young's modulus (stiffness): typical (handbook physical constant)Magnesium AZ31B-H24 · Density: nominalMagnesium AZ31B-H24 · Poisson's ratio: typical (handbook physical constant)Magnesium AZ91D · Poisson's ratio: base material: AZ91C casting (MIL-HDBK-5J handbook physical constant)Magnesium AZ31B-H24 · Max service temperature: stated application limit

Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.

Questions

Mechanical

Is Magnesium AZ31B-H24 stronger than Magnesium AZ91D?

Magnesium AZ31B-H24 is stronger: its yield strength is 220 MPa against 150 MPa for Magnesium AZ91D (47%).

Which is lighter, Magnesium AZ31B-H24 or Magnesium AZ91D?

Magnesium AZ31B-H24 is lighter: 1,769 kg/m³ against 1,810 kg/m³ for Magnesium AZ91D.

Which is stiffer, Magnesium AZ31B-H24 or Magnesium AZ91D?

Magnesium AZ91D is stiffer: Young's modulus 45 GPa against 44.8 GPa for Magnesium AZ31B-H24, so the same part in Magnesium AZ91D deflects less under the same load.

Which is lighter for the same job, Magnesium AZ31B-H24 or Magnesium AZ91D?

For the same stiffness or strength: Magnesium AZ31B-H24 is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.

Part that must be	Magnesium AZ31B-H24	Magnesium AZ91D
Stiff rod or tie (tension)	lighter	2% heavier
Stiff beam (bending)	lighter	2% heavier
Stiff panel or plate	lighter	2% heavier
Strong rod or tie	lighter	1.5x heavier
Strong beam	lighter	32% heavier
Strong panel or plate	lighter	24% heavier

For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).

Which is more ductile, Magnesium AZ31B-H24 or Magnesium AZ91D?

Magnesium AZ31B-H24 stretches further before it breaks: 13% elongation at break against 3% for Magnesium AZ91D.

Thermal

Which conducts heat better, Magnesium AZ31B-H24 or Magnesium AZ91D?

Magnesium AZ31B-H24 conducts heat better: 76.9 W/m·K against 72 W/m·K for Magnesium AZ91D.

Which expands less with temperature?

Magnesium AZ91D expands less: 25 µm/m·K against 26.8 µm/m·K for Magnesium AZ31B-H24.