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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Sources3 documents: Kaiser Aluminum, Magnesium Elektron, U.S. Department of Defense
Aluminum 3003-O
3003-O (annealed) aluminium-manganese alloy, the heat-exchanger tube and brazing alloy, Kaiser Aluminum Tube & Pipe Alloy 3003 Technical Data (Rev. 05/06), typical properties; specific heat from the NIST cryogenic 3003-F fit at 293 K.
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
Alloy 3003 Tube & Pipe Technical Data, Rev. 05/06Kaiser Aluminumarchived copyAluminum 3003-O · Yield strength: typical, O, 0.0625 in specimenAluminum 3003-O · Ultimate tensile strength: typical, OAluminum 3003-O · Elongation at break: typical, O, in 4DAluminum 3003-O · Young's modulus (stiffness): typicalAluminum 3003-O · Density: nominal, 20 °CAluminum 3003-O · Thermal conductivity: typical, O, 20 °CAluminum 3003-O · Thermal expansion: typical, mean 20-100 °CAluminum 3003-O · Melting point: melting range
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 AZ91D · Poisson's ratio: base material: AZ91C casting (MIL-HDBK-5J handbook physical constant)
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 3003-O stronger than Magnesium AZ91D?
Magnesium AZ91D is stronger: its yield strength is 150 MPa against 40 MPa for Aluminum 3003-O (3.75x).
Which is lighter, Aluminum 3003-O or Magnesium AZ91D?
Magnesium AZ91D is lighter: 1,810 kg/m³ against 2,730 kg/m³ for Aluminum 3003-O.
Which is stiffer, Aluminum 3003-O or Magnesium AZ91D?
Aluminum 3003-O is stiffer: Young's modulus 69 GPa against 45 GPa for Magnesium AZ91D, so the same part in Aluminum 3003-O deflects less under the same load.
Which is lighter for the same job, Aluminum 3003-O or Magnesium AZ91D?
For the same stiffness or strength: Aluminum 3003-O is lighter for a stiff rod or tie (tension); Magnesium AZ91D 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 3003-O
Magnesium AZ91D
Stiff rod or tie (tension)
lighter
2% heavier
Stiff beam (bending)
22% heavier
lighter
Stiff panel or plate
31% heavier
lighter
Strong rod or tie
5.66x heavier
lighter
Strong beam
3.64x heavier
lighter
Strong panel or plate
2.92x 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 3003-O or Magnesium AZ91D?
Aluminum 3003-O stretches further before it breaks: 30% elongation at break against 3% for Magnesium AZ91D.
Thermal
Which conducts heat better, Aluminum 3003-O or Magnesium AZ91D?
Aluminum 3003-O conducts heat better: 193 W/m·K against 72 W/m·K for Magnesium AZ91D.
Which expands less with temperature?
Aluminum 3003-O expands less: 23.2 µm/m·K against 25 µm/m·K for Magnesium AZ91D.