C36000 free-cutting brass, H02 half-hard rod 1 in. section (20% cold work), copper.org typical values
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 Brass C360 stronger than Magnesium AZ91D?
Brass C360 is stronger: its yield strength is 310 MPa against 150 MPa for Magnesium AZ91D (2.07x).
Which is lighter, Brass C360 or Magnesium AZ91D?
Magnesium AZ91D is lighter: 1,810 kg/m³ against 8,498 kg/m³ for Brass C360.
Which is stiffer, Brass C360 or Magnesium AZ91D?
Brass C360 is stiffer: Young's modulus 96.5 GPa against 45 GPa for Magnesium AZ91D, so the same part in Brass C360 deflects less under the same load.
Which is lighter for the same job, Brass C360 or Magnesium AZ91D?
For the same stiffness or strength: Magnesium AZ91D is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.
Part that must be
Brass C360
Magnesium AZ91D
Stiff rod or tie (tension)
2.19x heavier
lighter
Stiff beam (bending)
3.21x heavier
lighter
Stiff panel or plate
3.64x heavier
lighter
Strong rod or tie
2.27x heavier
lighter
Strong beam
2.89x heavier
lighter
Strong panel or plate
3.27x 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, Brass C360 or Magnesium AZ91D?
Brass C360 conducts heat better: 116 W/m·K against 72 W/m·K for Magnesium AZ91D.
Which expands less with temperature?
Brass C360 expands less: 20.5 µm/m·K against 25 µm/m·K for Magnesium AZ91D.