Aluminum A380 vs. Magnesium AZ31B-H24

Compare Aluminum A380 vs. Magnesium AZ31B-H24 strength, stiffness, weight and thermal properties.

Mechanical	Aluminum A380	Magnesium AZ31B-H24
Yield strength	160MPa1	220MPa238% stronger
Ultimate tensile strength	320MPa1	290MPa2
Elongation at break	3.5%1	13%23.71x more ductile
Young's modulus (stiffness)	71GPa11.58x stiffer	44.8GPa3
Density	2,713kg/m³1	1,769kg/m³31.53x lighter
Strength to weight	59kN·m/kg	124kN·m/kg2.11x higher
Stiffness to weight	26.2MN·m/kg3% higher	25.3MN·m/kg
Poisson's ratio	0.334	0.353
Shear modulus	26.7GPa1.61x stiffer in shear	16.6GPa
Bulk modulus	69.6GPa40% higher	49.8GPa
Speed of sound	5,116m/s2% faster	5,032m/s

Stiffness against densityHigher and further left: stiffer for its weight

Strength against densityHigher and further left: stronger for its weight

Thermal	Aluminum A380	Magnesium AZ31B-H24
Thermal conductivity	96.2W/m·K125% more heat through a fin	76.9W/m·K2
Thermal expansion	21.8µm/m·K123% less	26.8µm/m·K2
100 mm part over a 50 °C swing	109µm growth23% less	134µm growth
Specific heat	963J/kg·K1	1,040J/kg·K2
Heats up and cools (diffusivity)	36.8mm²/s	41.8mm²/s14% faster
Thermal shock resistance	6,669W/m	9,159W/m37% more resistant
Max service temperature	not sourced	149°C3

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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Sources4 documents: Rheocast Company, Magnesium Elektron, U.S. Department of Defense, North American Die Casting Association

Aluminum A380: A380 aluminium high-pressure die-casting alloy, typical properties; Rheocast Company (aluminium die caster, Germantown WI) A380 alloy data page.
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

1
Alloy Aluminum: A380Rheocast CompanyAluminum A380 · Yield strength: typical, 25 °CAluminum A380 · Ultimate tensile strength: typical, 25 °CAluminum A380 · Elongation at break: typicalAluminum A380 · Young's modulus (stiffness): typical, 25 °CAluminum A380 · Density: typical at 68 °FAluminum A380 · Thermal conductivity: typical at 68 °FAluminum A380 · Thermal expansion: typical, 68-572 °F (20-300 °C)Aluminum A380 · Specific heat: typical at 68 °F
2
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
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 AZ31B-H24 · Max service temperature: stated application limit
4
Product Design for Die Casting, Table 4.1: Die Casting Alloys Material Properties ComparisonNorth American Die Casting Associationarchived copyAluminum A380 · Poisson's ratio: typical, as-cast, separately die cast specimens

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 Aluminum A380 stronger than Magnesium AZ31B-H24?

Magnesium AZ31B-H24 is stronger: its yield strength is 220 MPa against 160 MPa for Aluminum A380 (38%).

Which is lighter, Aluminum A380 or Magnesium AZ31B-H24?

Magnesium AZ31B-H24 is lighter: 1,769 kg/m³ against 2,713 kg/m³ for Aluminum A380.

Which is stiffer, Aluminum A380 or Magnesium AZ31B-H24?

Aluminum A380 is stiffer: Young's modulus 71 GPa against 44.8 GPa for Magnesium AZ31B-H24, so the same part in Aluminum A380 deflects less under the same load.

Which is lighter for the same job, Aluminum A380 or Magnesium AZ31B-H24?

For the same stiffness or strength: Aluminum A380 is lighter for a stiff rod or tie (tension); Magnesium AZ31B-H24 is lighter for a stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.

Part that must be	Aluminum A380	Magnesium AZ31B-H24
Stiff rod or tie (tension)	lighter	3% heavier
Stiff beam (bending)	22% heavier	lighter
Stiff panel or plate	32% heavier	lighter
Strong rod or tie	2.11x heavier	lighter
Strong beam	1.9x heavier	lighter
Strong panel or plate	1.8x heavier	lighter

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, Aluminum A380 or Magnesium AZ31B-H24?

Magnesium AZ31B-H24 stretches further before it breaks: 13% elongation at break against 3.5% for Aluminum A380.

Thermal

Which conducts heat better, Aluminum A380 or Magnesium AZ31B-H24?

Aluminum A380 conducts heat better: 96.2 W/m·K against 76.9 W/m·K for Magnesium AZ31B-H24.

Which expands less with temperature?

Aluminum A380 expands less: 21.8 µm/m·K against 26.8 µm/m·K for Magnesium AZ31B-H24.