6061-T6/T651, Kaiser Aluminum typical properties; Poisson from MIL-HDBK-5J
ELEKTRON AZ91D magnesium die-casting alloy, as cast; Magnesium Elektron datasheet 475 (7/01), typical properties; Poisson from MIL-HDBK-5J for AZ91C castings.
Every value links to the document that states it. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Is Aluminum 6061-T6 stronger than Magnesium AZ91D?
Aluminum 6061-T6 is stronger: its yield strength is 276 MPa against 150 MPa for Magnesium AZ91D (1.84x).
Which is lighter, Aluminum 6061-T6 or Magnesium AZ91D?
Magnesium AZ91D is lighter: 1,810 kg/m³ against 2,700 kg/m³ for Aluminum 6061-T6.
Which is stiffer, Aluminum 6061-T6 or Magnesium AZ91D?
Aluminum 6061-T6 is stiffer: Young's modulus 68.3 GPa against 45 GPa for Magnesium AZ91D, so the same part in Aluminum 6061-T6 deflects less under the same load.
Which is lighter for the same job, Aluminum 6061-T6 or Magnesium AZ91D?
For the same stiffness or strength: Aluminum 6061-T6 is lighter for a stiff rod or tie (tension), strong rod or tie; Magnesium AZ91D is lighter for a stiff beam (bending), stiff panel or plate, strong panel or plate.
Part that must be
Aluminum 6061-T6
Magnesium AZ91D
Stiff rod or tie (tension)
lighter
2% heavier
Stiff beam (bending)
21% heavier
lighter
Stiff panel or plate
30% heavier
lighter
Strong rod or tie
lighter
23% heavier
Strong beam
about equal
about equal
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 conducts heat better, Aluminum 6061-T6 or Magnesium AZ91D?
Aluminum 6061-T6 conducts heat better: 167 W/m·K against 72 W/m·K for Magnesium AZ91D.
Which expands less with temperature?
Aluminum 6061-T6 expands less: 23.6 µm/m·K against 25 µm/m·K for Magnesium AZ91D.