Magnesium AZ91D vs. Plastic LCP GF30

Compare Magnesium AZ91D vs. Plastic LCP GF30 strength, stiffness, weight and thermal properties.

Plastic LCP GF30Bulk polymer (molded or machined)

Mechanical	Magnesium AZ91D	Plastic LCP GF30
Yield strength	150MPa1	not given (tensile used)
Ultimate tensile strength	230MPa12x stronger	tensile strength115MPa2
Flexural strength	not sourced	184MPa2
Elongation at break	3%12x more ductile	tensile elongation1.5%2
Young's modulus (stiffness)	45GPa13.91x stiffer	tensile modulus11.5GPa2
Density	1,810kg/m³1	1,610kg/m³212% lighter
Strength to weight	82.9kN·m/kg16% higher	71.4kN·m/kg
Stiffness to weight	24.9MN·m/kg3.48x higher	7.14MN·m/kg
Poisson's ratio	base material0.353	not sourced
Shear modulus	16.7GPa	not sourced
Bulk modulus	50GPa	not sourced
Speed of sound	4,986m/s1.87x faster	2,673m/s

Stiffness against densityHigher and further left: stiffer for its weight

Strength against densityHigher and further left: stronger for its weight

Thermal	Magnesium AZ91D	Plastic LCP GF30
Thermal conductivity	72W/m·K1144x more heat through a fin	hot disk0.5W/m·K2
Thermal expansion	25µm/m·K1	flow direction20µm/m·K225% less
100 mm part over a 50 °C swing	125µm growth	100µm growth25% less
Specific heat	1,050J/kg·K125% higher	ASTM E1269839J/kg·K2
Heats up and cools (diffusivity)	37.9mm²/s102x faster	0.37mm²/s
Thermal shock resistance	6,240W/m	not sourced
Melting point	melting range470–595°C1	not sourced
Max service temperature	not sourced	HDT 1.8 MPa288°C2

Thermal conductivity against densityHigher and further left: spreads more heat for its weight

Thermal expansion against thermal conductivityLower and further right: warps less when heated

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Sources3 documents: Magnesium Elektron, Sumitomo Chemical, U.S. Department of Defense

Magnesium AZ91D: ELEKTRON AZ91D magnesium die-casting alloy, as cast; Magnesium Elektron datasheet 475 (7/01), typical properties; Poisson from MIL-HDBK-5J for AZ91C castings.
Plastic LCP GF30: Sumitomo Chemical SUMIKASUPER LCP E6006L (30% glass fibre; high strength, low shrinkage); SUMIKASUPER LCP Technical Note, Version 04 / Nov. 2023, typical values.

1
Elektron Die Casting Alloys (Datasheet 475)Magnesium Elektronarchived copyMagnesium AZ91D · Yield strength: typical, 0.2% tensile yield, ambient temperatureMagnesium AZ91D · Ultimate tensile strength: typical, ambient temperatureMagnesium AZ91D · Elongation at break: typical, ambient temperatureMagnesium AZ91D · Young's modulus (stiffness): typicalMagnesium AZ91D · Density: typicalMagnesium AZ91D · Thermal conductivity: typicalMagnesium AZ91D · Thermal expansion: typical, temperature range not statedMagnesium AZ91D · Specific heat: typicalMagnesium AZ91D · Melting point: melting range
2
SUMIKASUPER LCP Technical Note, Version 04 (2023)Sumitomo Chemicalarchived copyPlastic LCP GF30 · Ultimate tensile strength: tensile strength (ISO 527)Plastic LCP GF30 · Flexural strength: typical (ISO 178)Plastic LCP GF30 · Elongation at break: tensile elongation (ISO 527)Plastic LCP GF30 · Young's modulus (stiffness): tensile modulus (ISO 527)Plastic LCP GF30 · Density: typicalPlastic LCP GF30 · Thermal conductivity: hot disk (ISO 22007-2), temperature not statedPlastic LCP GF30 · Thermal expansion: flow direction (MD), mean 50-150 °CPlastic LCP GF30 · Specific heat: ASTM E1269, temperature not statedPlastic LCP GF30 · Max service temperature: HDT 1.8 MPa (ISO 75)
3
MIL-HDBK-5J, Metallic Materials and Elements for Aerospace Vehicle Structures (2003)U.S. Department of DefenseMagnesium AZ91D · Poisson's ratio: base material: AZ91C casting (MIL-HDBK-5J handbook physical constant)

Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.

Questions

Mechanical

Is Magnesium AZ91D stronger than Plastic LCP GF30?

Magnesium AZ91D is stronger: its yield strength is 150 MPa against tensile strength 115 MPa for Plastic LCP GF30 (30%).

Which is lighter, Magnesium AZ91D or Plastic LCP GF30?

Plastic LCP GF30 is lighter: 1,610 kg/m³ against 1,810 kg/m³ for Magnesium AZ91D.

Which is stiffer, Magnesium AZ91D or Plastic LCP GF30?

Magnesium AZ91D is stiffer: Young's modulus 45 GPa against 11.5 GPa for Plastic LCP GF30, so the same part in Magnesium AZ91D deflects less under the same load.

Which is lighter for the same job, Magnesium AZ91D or Plastic LCP GF30?

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 LCP GF30
Stiff rod or tie (tension)	lighter	3.48x heavier
Stiff beam (bending)	lighter	1.76x heavier
Stiff panel or plate	lighter	40% heavier
Strong rod or tie	lighter	16% heavier
Strong beam	lighter	6% heavier
Strong panel or plate	lighter	2% 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 is more ductile, Magnesium AZ91D or Plastic LCP GF30?

Magnesium AZ91D stretches further before it breaks: 3% elongation at break against 1.5% for Plastic LCP GF30.

Thermal

Which conducts heat better, Magnesium AZ91D or Plastic LCP GF30?

Magnesium AZ91D conducts heat better: 72 W/m·K against 0.5 W/m·K for Plastic LCP GF30.

Which expands less with temperature?

Plastic LCP GF30 expands less: 20 µm/m·K against 25 µm/m·K for Magnesium AZ91D.