Materials / Compare
Magnesium AZ91D vs. Plastic PEEK
Compare Magnesium AZ91D vs. Plastic PEEK strength, stiffness, weight and thermal properties.
| Try it on a partA bracket to run stress or thermal on, free in your browser | Open in LessCAD | Open in LessCAD |
|---|---|---|
| Mechanical | ||
| Yield strength | 150MPasourcetypical, 0.2% tensile yield, ambient temperature | 98MPasourcetypical, tensile yield |
| Ultimate tensile strength | 230MPasourcetypical, ambient temperature | not sourced |
| Compressive strength | not sourced | 125MPasourcetypical, 23 C |
| Flexural strength | not sourced | 165MPasourcetypical, flexural stress at yield, 23 C |
| Elongation at break | 3%sourcetypical, ambient temperature | 25%sourcetypical, at break |
| Young's modulus (stiffness) | 45GPasourcetypical | 4GPasourcetypical (nominal) |
| Density | 1,810kg/m³sourcetypical | 1,300kg/m³sourcetypical (crystalline) |
| Strength to weight | 82.9kN·m/kg10% higher | 75.4kN·m/kg |
| Stiffness to weight | 24.9MN·m/kg8.08x higher | 3.08MN·m/kg |
| Poisson's ratio | 0.35sourcebase material: AZ91C casting (MIL-HDBK-5J handbook physical constant) | 0.38sourcetypical |
| Shear modulus | 16.7GPa11.5x stiffer in shear | 1.45GPa |
| Bulk modulus | 50GPa | 5.56GPa |
| Speed of sound | 4,986m/s | 1,754m/s |
| Thermal | ||
| Thermal conductivity | 72W/m·Ksourcetypical | 0.29W/m·Ksourcetypical, average, 23 C |
| Thermal expansion | 25µm/m·Ksourcetypical, temperature range not stated | 55µm/m·Ksourceaverage of flow/cross-flow, below Tg (<143 C) |
| 100 mm part over a 50 °C swing | 125µm growth2.2x less | 275µm growth |
| Specific heat | 1,050J/kg·Ksourcetypical | 2,200J/kg·Ksourcetypical, 23 °C, DSC (Victrex PEEK 450G TDS, revision Jul 2012) |
| Heats up and cools (diffusivity) | 37.9mm²/s374x faster | 0.101mm²/s |
| Thermal shock resistance | 6,240W/m77.9x more resistant | 80.1W/m |
| Melting point | 470–595°Csourcemelting range | 343°Csourcetypical, DSC |
| Glass transition | not sourced | 143°Csourceonset (midpoint 150 C) |
| Max service temperature | not sourced | 240°CsourceUL 746B RTI, mechanical strength (continuous use index) |
| Values for | ELEKTRON AZ91D magnesium die-casting alloy, as cast; Magnesium Elektron datasheet 475 (7/01), typical properties; Poisson from MIL-HDBK-5J for AZ91C castings. | Victrex PEEK 450G (unreinforced, injection moulded), Victrex TDS rev. March 2026; Poisson from Victrex fluid-management flyer (2020-07) |
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 PEEK?
Magnesium AZ91D is stronger: its yield strength is 150 MPa against 98 MPa for Plastic PEEK (1.53x).
Which is lighter, Magnesium AZ91D or Plastic PEEK?
Plastic PEEK is lighter: 1,300 kg/m³ against 1,810 kg/m³ for Magnesium AZ91D.
Which is stiffer, Magnesium AZ91D or Plastic PEEK?
Magnesium AZ91D is stiffer: Young's modulus 45 GPa against 4 GPa for Plastic PEEK, so the same part in Magnesium AZ91D deflects less under the same load.
Which is lighter for the same job, Magnesium AZ91D or Plastic PEEK?
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; Plastic PEEK is lighter for a strong beam, strong panel or plate.
| Part that must be | Magnesium AZ91D | Plastic PEEK |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 8.08x heavier |
| Stiff beam (bending) | lighter | 2.41x heavier |
| Stiff panel or plate | lighter | 1.61x heavier |
| Strong rod or tie | lighter | 10% heavier |
| Strong beam | 5% heavier | lighter |
| Strong panel or plate | 13% 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 PEEK?
Magnesium AZ91D conducts heat better: 72 W/m·K against 0.29 W/m·K for Plastic PEEK.
Which expands less with temperature?
Magnesium AZ91D expands less: 25 µm/m·K against 55 µm/m·K for Plastic PEEK.