Thermal conductivity against densityHigher and further left: spreads more heat for its weightThermal expansion against thermal conductivityLower and further right: warps less when heated
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Alloy 7075 Rod & Bar Technical DataKaiser Aluminumarchived copyAluminum 7075-T6 · Yield strength: typical, 0.2% offset, .500 in dia specimenAluminum 7075-T6 · Ultimate tensile strength: typicalAluminum 7075-T6 · Elongation at break: typical, in 4DAluminum 7075-T6 · Young's modulus (stiffness): typical
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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
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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 7075-T6 · 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
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Alloy 7075 Sheet, Coil & Plate Technical DataKaiser Aluminumarchived copyAluminum 7075-T6 · Density: nominalAluminum 7075-T6 · Thermal conductivity: typical, 20 °C, T651Aluminum 7075-T6 · Thermal expansion: typical, mean 20-100 °CAluminum 7075-T6 · Specific heat: typical, at 100 °CAluminum 7075-T6 · Melting point: melting range
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 7075-T6 stronger than Magnesium AZ31B-H24?
Aluminum 7075-T6 is stronger: its yield strength is 503 MPa against 220 MPa for Magnesium AZ31B-H24 (2.29x).
Which is lighter, Aluminum 7075-T6 or Magnesium AZ31B-H24?
Magnesium AZ31B-H24 is lighter: 1,769 kg/m³ against 2,800 kg/m³ for Aluminum 7075-T6.
Which is stiffer, Aluminum 7075-T6 or Magnesium AZ31B-H24?
Aluminum 7075-T6 is stiffer: Young's modulus 71 GPa against 44.8 GPa for Magnesium AZ31B-H24, so the same part in Aluminum 7075-T6 deflects less under the same load.
Which is lighter for the same job, Aluminum 7075-T6 or Magnesium AZ31B-H24?
For the same stiffness or strength: Aluminum 7075-T6 is lighter for a strong rod or tie, strong beam; Magnesium AZ31B-H24 is lighter for a stiff beam (bending), stiff panel or plate, strong panel or plate.
Part that must be
Aluminum 7075-T6
Magnesium AZ31B-H24
Stiff rod or tie (tension)
about equal
about equal
Stiff beam (bending)
26% heavier
lighter
Stiff panel or plate
36% heavier
lighter
Strong rod or tie
lighter
44% heavier
Strong beam
lighter
10% heavier
Strong panel or plate
5% 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 7075-T6 or Magnesium AZ31B-H24?
Magnesium AZ31B-H24 stretches further before it breaks: 13% elongation at break against 11% for Aluminum 7075-T6.
Thermal
Which conducts heat better, Aluminum 7075-T6 or Magnesium AZ31B-H24?
Aluminum 7075-T6 conducts heat better: 130 W/m·K against 76.9 W/m·K for Magnesium AZ31B-H24.
Which expands less with temperature?
Aluminum 7075-T6 expands less: 23.4 µm/m·K against 26.8 µm/m·K for Magnesium AZ31B-H24.