ELEKTRON AZ91D magnesium die-casting alloy, as cast; Magnesium Elektron datasheet 475 (7/01), typical properties; Poisson from MIL-HDBK-5J for AZ91C castings.
Celanese Fortron 1140L4 (PPS, 40% glass fibre), injection moulding; FORTRON PPS Short-Term Properties Guide (PPS-012, 2016); thermal conductivity and Poisson for 40% glass-reinforced Fortron from the Fortron PPS Design Manual (PPS-050, 2013).
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 PPS GF40?
Plastic PPS GF40 is stronger: its tensile strength is 195 MPa against yield strength 150 MPa for Magnesium AZ91D (30%).
Which is lighter, Magnesium AZ91D or Plastic PPS GF40?
Plastic PPS GF40 is lighter: 1,650 kg/m³ against 1,810 kg/m³ for Magnesium AZ91D.
Which is stiffer, Magnesium AZ91D or Plastic PPS GF40?
Magnesium AZ91D is stiffer: Young's modulus 45 GPa against 14.7 GPa for Plastic PPS GF40, so the same part in Magnesium AZ91D deflects less under the same load.
Which is lighter for the same job, Magnesium AZ91D or Plastic PPS GF40?
For the same stiffness or strength: Magnesium AZ91D is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; Plastic PPS GF40 is lighter for a strong rod or tie, strong beam, strong panel or plate.
Part that must be
Magnesium AZ91D
Plastic PPS GF40
Stiff rod or tie (tension)
lighter
2.79x heavier
Stiff beam (bending)
lighter
1.59x heavier
Stiff panel or plate
lighter
32% heavier
Strong rod or tie
43% heavier
lighter
Strong beam
31% heavier
lighter
Strong panel or plate
25% 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, Magnesium AZ91D or Plastic PPS GF40?
Magnesium AZ91D conducts heat better: 72 W/m·K against 0.2 W/m·K for Plastic PPS GF40.
Which expands less with temperature?
Plastic PPS GF40 expands less: 12 µm/m·K against 25 µm/m·K for Magnesium AZ91D.