Magnesium AZ91D vs. Plastic Nylon PA6

Compare Magnesium AZ91D vs. Plastic Nylon PA6 strength, stiffness, weight and thermal properties.

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Plastic Nylon PA6Bulk polymer (molded or machined)

Mechanical
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Yield strength	150MPasourcetypical, 0.2% tensile yield, ambient temperature	90MPasourcetypical, dry
Ultimate tensile strength	230MPasourcetypical, ambient temperature	not sourced
Elongation at break	3%sourcetypical, ambient temperature	10%sourcenominal strain at break, dry
Young's modulus (stiffness)	45GPasourcetypical	3.5GPasourcetypical, dry
Density	1,810kg/m³sourcetypical	1,130kg/m³sourcetypical1.6x lighter
Strength to weight	82.9kN·m/kg4% higher	79.6kN·m/kg
Stiffness to weight	24.9MN·m/kg8.03x higher	3.1MN·m/kg
Poisson's ratio	0.35sourcebase material: AZ91C casting (MIL-HDBK-5J handbook physical constant)	0.4sourcebase material: unfilled polyamide (PA), conditioned, maker design-guide family value (Covestro Table 3-1)
Shear modulus	16.7GPa13.3x stiffer in shear	1.25GPa
Bulk modulus	50GPa	5.83GPa
Speed of sound	4,986m/s	1,760m/s
Thermal
Thermal conductivity	72W/m·Ksourcetypical218x more heat through a fin	0.33W/m·Ksourcetypical
Thermal expansion	25µm/m·Ksourcetypical, temperature range not stated	102µm/m·Ksourcelongitudinal, 23-55 °C
100 mm part over a 50 °C swing	125µm growth4.08x less	510µm growth
Specific heat	1,050J/kg·Ksourcetypical	1,700J/kg·Ksourcetypical
Heats up and cools (diffusivity)	37.9mm²/s221x faster	0.172mm²/s
Thermal shock resistance	6,240W/m125x more resistant	49.9W/m
Melting point	470–595°Csourcemelting range	220°CsourceDSC
Max service temperature	not sourced	87°CsourceIEC 60216 temperature index, 20000 h
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.	BASF Ultramid B3S (PA6, unreinforced injection-moulding grade), Product Information 02/2026, dry values (ISO methods)

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 Nylon PA6?

Magnesium AZ91D is stronger: its yield strength is 150 MPa against 90 MPa for Plastic Nylon PA6 (1.67x).

Which is lighter, Magnesium AZ91D or Plastic Nylon PA6?

Plastic Nylon PA6 is lighter: 1,130 kg/m³ against 1,810 kg/m³ for Magnesium AZ91D.

Which is stiffer, Magnesium AZ91D or Plastic Nylon PA6?

Magnesium AZ91D is stiffer: Young's modulus 45 GPa against 3.5 GPa for Plastic Nylon PA6, so the same part in Magnesium AZ91D deflects less under the same load.

Which is lighter for the same job, Magnesium AZ91D or Plastic Nylon PA6?

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 Nylon PA6 is lighter for a strong beam, strong panel or plate.

Part that must be	Magnesium AZ91D	Plastic Nylon PA6
Stiff rod or tie (tension)	lighter	8.03x heavier
Stiff beam (bending)	lighter	2.24x heavier
Stiff panel or plate	lighter	46% heavier
Strong rod or tie	lighter	4% heavier
Strong beam	14% heavier	lighter
Strong panel or plate	24% 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 Nylon PA6?

Magnesium AZ91D conducts heat better: 72 W/m·K against 0.33 W/m·K for Plastic Nylon PA6.

Which expands less with temperature?

Magnesium AZ91D expands less: 25 µm/m·K against 102 µm/m·K for Plastic Nylon PA6.

Among 72 materials

Stiffness against density

Strength against density