ELEKTRON AZ91D magnesium die-casting alloy, as cast; Magnesium Elektron datasheet 475 (7/01), typical properties; Poisson from MIL-HDBK-5J for AZ91C castings.
LyondellBasell Moplen HP501H polypropylene homopolymer (general purpose), typical ISO values
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 Magnesium AZ91D stronger than Plastic Polypropylene?
Magnesium AZ91D is stronger: its yield strength is 150 MPa against 33 MPa for Plastic Polypropylene (4.55x).
Which is lighter, Magnesium AZ91D or Plastic Polypropylene?
Plastic Polypropylene is lighter: 900 kg/m³ against 1,810 kg/m³ for Magnesium AZ91D.
Which is stiffer, Magnesium AZ91D or Plastic Polypropylene?
Magnesium AZ91D is stiffer: Young's modulus 45 GPa against 1.45 GPa for Plastic Polypropylene, so the same part in Magnesium AZ91D deflects less under the same load.
Which is lighter for the same job, Magnesium AZ91D or Plastic Polypropylene?
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
Magnesium AZ91D
Plastic Polypropylene
Stiff rod or tie (tension)
lighter
15.4x heavier
Stiff beam (bending)
lighter
2.77x heavier
Stiff panel or plate
lighter
1.56x heavier
Strong rod or tie
lighter
2.26x heavier
Strong beam
lighter
36% heavier
Strong panel or plate
lighter
6% heavier
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, Magnesium AZ91D or Plastic Polypropylene?
Magnesium AZ91D conducts heat better: 72 W/m·K against 0.195 W/m·K for Plastic Polypropylene.
Which expands less with temperature?
Magnesium AZ91D expands less: 25 µm/m·K against 90 µm/m·K for Plastic Polypropylene.