Aluminum 7050-T7451 vs. Magnesium AZ31B-H24

Compare Aluminum 7050-T7451 vs. Magnesium AZ31B-H24 strength, stiffness, weight and thermal properties.

Mechanical	Aluminum 7050-T7451	Magnesium AZ31B-H24
Yield strength	469MPa12.13x stronger	220MPa2
Ultimate tensile strength	524MPa11.81x stronger	290MPa2
Elongation at break	11%1	13%218% more ductile
Young's modulus (stiffness)	70.3GPa11.57x stiffer	44.8GPa3
Density	2,830kg/m³1	1,769kg/m³31.6x lighter
Strength to weight	166kN·m/kg33% higher	124kN·m/kg
Stiffness to weight	24.8MN·m/kg	25.3MN·m/kg2% higher
Poisson's ratio	0.333	0.353
Shear modulus	26.4GPa1.59x stiffer in shear	16.6GPa
Bulk modulus	68.9GPa38% higher	49.8GPa
Speed of sound	4,984m/s	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 7050-T7451	Magnesium AZ31B-H24
Thermal conductivity	157W/m·K12.04x more heat through a fin	76.9W/m·K2
Thermal expansion	23.5µm/m·K114% less	26.8µm/m·K2
100 mm part over a 50 °C swing	118µm growth14% less	134µm growth
Specific heat	860J/kg·K1	1,040J/kg·K221% higher
Heats up and cools (diffusivity)	64.5mm²/s1.54x faster	41.8mm²/s
Thermal shock resistance	29,862W/m3.26x more resistant	9,159W/m
Melting point	melting range524–635°C1	not sourced
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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Sources3 documents: Kaiser Aluminum, Magnesium Elektron, U.S. Department of Defense

Aluminum 7050-T7451: 7050-T7451 plate, Kaiser Aluminum sheet, coil & plate typical datasheet (longitudinal); Poisson from MIL-HDBK-5J
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 7050 Sheet, Coil & Plate Technical DataKaiser Aluminumarchived copyAluminum 7050-T7451 · Yield strength: typical, longitudinal, 0.2% offsetAluminum 7050-T7451 · Ultimate tensile strength: typical, longitudinalAluminum 7050-T7451 · Elongation at break: typical, longitudinalAluminum 7050-T7451 · Young's modulus (stiffness): typicalAluminum 7050-T7451 · Density: nominalAluminum 7050-T7451 · Thermal conductivity: typical, 20 °CAluminum 7050-T7451 · Thermal expansion: typical, mean 20-100 °CAluminum 7050-T7451 · Specific heat: typical, at 100 °CAluminum 7050-T7451 · Melting point: melting range
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: nominalAluminum 7050-T7451 · Poisson's ratio: typical (handbook physical constant)Magnesium AZ31B-H24 · Poisson's ratio: typical (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 Aluminum 7050-T7451 stronger than Magnesium AZ31B-H24?

Aluminum 7050-T7451 is stronger: its yield strength is 469 MPa against 220 MPa for Magnesium AZ31B-H24 (2.13x).

Which is lighter, Aluminum 7050-T7451 or Magnesium AZ31B-H24?

Magnesium AZ31B-H24 is lighter: 1,769 kg/m³ against 2,830 kg/m³ for Aluminum 7050-T7451.

Which is stiffer, Aluminum 7050-T7451 or Magnesium AZ31B-H24?

Aluminum 7050-T7451 is stiffer: Young's modulus 70.3 GPa against 44.8 GPa for Magnesium AZ31B-H24, so the same part in Aluminum 7050-T7451 deflects less under the same load.

Which is lighter for the same job, Aluminum 7050-T7451 or Magnesium AZ31B-H24?

For the same stiffness or strength: Aluminum 7050-T7451 is lighter for a strong rod or tie, strong beam; Magnesium AZ31B-H24 is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong panel or plate.

Part that must be	Aluminum 7050-T7451	Magnesium AZ31B-H24
Stiff rod or tie (tension)	2% heavier	lighter
Stiff beam (bending)	28% heavier	lighter
Stiff panel or plate	38% heavier	lighter
Strong rod or tie	lighter	33% heavier
Strong beam	lighter	4% heavier
Strong panel or plate	10% 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 7050-T7451 or Magnesium AZ31B-H24?

Magnesium AZ31B-H24 stretches further before it breaks: 13% elongation at break against 11% for Aluminum 7050-T7451.

Thermal

Which conducts heat better, Aluminum 7050-T7451 or Magnesium AZ31B-H24?

Aluminum 7050-T7451 conducts heat better: 157 W/m·K against 76.9 W/m·K for Magnesium AZ31B-H24.

Which expands less with temperature?

Aluminum 7050-T7451 expands less: 23.5 µm/m·K against 26.8 µm/m·K for Magnesium AZ31B-H24.