Aluminum 2024-T351 vs. Magnesium AZ91D

Compare Aluminum 2024-T351 vs. Magnesium AZ91D strength, stiffness, weight and thermal properties.

Change either side

Aluminum 2024-T351Wrought

Mechanical
Try it on a partA bracket to run stress or thermal on, free in your browser	Open in LessCAD	Open in LessCAD
Yield strength	324MPasourcetypical, 0.2% offset, .500 in dia specimen	150MPasourcetypical, 0.2% tensile yield, ambient temperature
Ultimate tensile strength	469MPasourcetypical	230MPasourcetypical, ambient temperature
Elongation at break	19%sourcetypical, in 4D	3%sourcetypical, ambient temperature
Young's modulus (stiffness)	73.1GPasourcetypical1.62x stiffer	45GPasourcetypical
Density	2,770kg/m³sourcenominal	1,810kg/m³sourcetypical
Strength to weight	117kN·m/kg41% higher	82.9kN·m/kg
Stiffness to weight	26.4MN·m/kg6% higher	24.9MN·m/kg
Poisson's ratio	0.33sourcetypical (handbook physical constant), all tempers	0.35sourcebase material: AZ91C casting (MIL-HDBK-5J handbook physical constant)
Shear modulus	27.5GPa1.65x stiffer in shear	16.7GPa
Bulk modulus	71.7GPa	50GPa
Speed of sound	5,137m/s	4,986m/s
Thermal
Thermal conductivity	120W/m·Ksourcetypical, 20 °C	72W/m·Ksourcetypical
Thermal expansion	22.9µm/m·Ksourcetypical, mean 20-100 °C	25µm/m·Ksourcetypical, temperature range not stated
100 mm part over a 50 °C swing	115µm growth9% less	125µm growth
Specific heat	875J/kg·Ksourcetypical, at 100 °C	1,050J/kg·Ksourcetypical
Heats up and cools (diffusivity)	49.5mm²/s31% faster	37.9mm²/s
Thermal shock resistance	15,561W/m2.49x more resistant	6,240W/m
Melting point	502–638°Csourcemelting range	470–595°Csourcemelting range
Values for	2024-T4/T351, Kaiser Aluminum sheet, coil & plate typical datasheet; Poisson from MIL-HDBK-5J	ELEKTRON AZ91D magnesium die-casting alloy, as cast; Magnesium Elektron datasheet 475 (7/01), typical properties; Poisson from MIL-HDBK-5J for AZ91C castings.

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 Aluminum 2024-T351 stronger than Magnesium AZ91D?

Aluminum 2024-T351 is stronger: its yield strength is 324 MPa against 150 MPa for Magnesium AZ91D (2.16x).

Which is lighter, Aluminum 2024-T351 or Magnesium AZ91D?

Magnesium AZ91D is lighter: 1,810 kg/m³ against 2,770 kg/m³ for Aluminum 2024-T351.

Which is stiffer, Aluminum 2024-T351 or Magnesium AZ91D?

Aluminum 2024-T351 is stiffer: Young's modulus 73.1 GPa against 45 GPa for Magnesium AZ91D, so the same part in Aluminum 2024-T351 deflects less under the same load.

Which is lighter for the same job, Aluminum 2024-T351 or Magnesium AZ91D?

For the same stiffness or strength: Aluminum 2024-T351 is lighter for a stiff rod or tie (tension), strong rod or tie, strong beam; Magnesium AZ91D is lighter for a stiff beam (bending), stiff panel or plate, strong panel or plate.

Part that must be	Aluminum 2024-T351	Magnesium AZ91D
Stiff rod or tie (tension)	lighter	6% heavier
Stiff beam (bending)	20% heavier	lighter
Stiff panel or plate	30% heavier	lighter
Strong rod or tie	lighter	41% heavier
Strong beam	lighter	9% heavier
Strong panel or plate	4% 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, Aluminum 2024-T351 or Magnesium AZ91D?

Aluminum 2024-T351 conducts heat better: 120 W/m·K against 72 W/m·K for Magnesium AZ91D.

Which expands less with temperature?

Aluminum 2024-T351 expands less: 22.9 µm/m·K against 25 µm/m·K for Magnesium AZ91D.

Among 72 materials

Stiffness against density

Strength against density