Aluminum ADC12 vs. Magnesium AZ91D

Compare Aluminum ADC12 vs. Magnesium AZ91D strength, stiffness, weight and thermal properties.

Change either side

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	149MPasourceone test result, 0.2% proof stress, as cast, ASTM tensile bar (Daiki)	150MPasourcetypical, 0.2% tensile yield, ambient temperature
Ultimate tensile strength	345MPasourceone test result, as cast, ASTM tensile bar (Daiki)	230MPasourcetypical, ambient temperature
Elongation at break	2.3%sourceone test result, as cast, ASTM tensile bar (Daiki)	3%sourcetypical, ambient temperature
Young's modulus (stiffness)	79.8GPasourcestandard value (S.S.Aluminum)	45GPasourcetypical
Density	2,680kg/m³sourcemeasured (Daiki)	1,810kg/m³sourcetypical
Strength to weight	55.6kN·m/kg	82.9kN·m/kg49% higher
Stiffness to weight	29.8MN·m/kg20% higher	24.9MN·m/kg
Poisson's ratio	not sourced	0.35sourcebase material: AZ91C casting (MIL-HDBK-5J handbook physical constant)
Shear modulus	not sourced	16.7GPa
Bulk modulus	not sourced	50GPa
Speed of sound	5,457m/s	4,986m/s
Thermal
Thermal conductivity	125W/m·Ksourcemeasured on specimens cut from a 50 x 100 x 5 mm flat die casting (Daiki)	72W/m·Ksourcetypical
Thermal expansion	21µm/m·Ksourcemeasured, temperature range not stated (Daiki)	25µm/m·Ksourcetypical, temperature range not stated
100 mm part over a 50 °C swing	105µm growth19% less	125µm growth
Specific heat	911J/kg·Ksourcemeasured (Daiki)	1,050J/kg·Ksourcetypical
Heats up and cools (diffusivity)	51.2mm²/s35% faster	37.9mm²/s
Thermal shock resistance	not sourced	6,240W/m
Melting point	515–582°Csourcesolidus-liquidus (Daiki)	470–595°Csourcemelting range
Values for	JIS ADC12 (Al-Si-Cu, about A383 / EN AC-46100) high-pressure die-casting alloy, as cast; physical properties from Daiki Aluminium Industry (ADC12 ingot producer) measured values; modulus from S.S.Aluminum (ADC12 ingot producer) standard values.	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 ADC12 stronger than Magnesium AZ91D?

Magnesium AZ91D is stronger: its yield strength is 150 MPa against 149 MPa for Aluminum ADC12 (1%).

Which is lighter, Aluminum ADC12 or Magnesium AZ91D?

Magnesium AZ91D is lighter: 1,810 kg/m³ against 2,680 kg/m³ for Aluminum ADC12.

Which is stiffer, Aluminum ADC12 or Magnesium AZ91D?

Aluminum ADC12 is stiffer: Young's modulus 79.8 GPa against 45 GPa for Magnesium AZ91D, so the same part in Aluminum ADC12 deflects less under the same load.

Which is lighter for the same job, Aluminum ADC12 or Magnesium AZ91D?

For the same stiffness or strength: Aluminum ADC12 is lighter for a stiff rod or tie (tension); Magnesium AZ91D is lighter for a stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.

Part that must be	Aluminum ADC12	Magnesium AZ91D
Stiff rod or tie (tension)	lighter	20% heavier
Stiff beam (bending)	11% heavier	lighter
Stiff panel or plate	22% heavier	lighter
Strong rod or tie	49% heavier	lighter
Strong beam	49% heavier	lighter
Strong panel or plate	49% 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 ADC12 or Magnesium AZ91D?

Aluminum ADC12 conducts heat better: 125 W/m·K against 72 W/m·K for Magnesium AZ91D.

Which expands less with temperature?

Aluminum ADC12 expands less: 21 µm/m·K against 25 µm/m·K for Magnesium AZ91D.

Among 72 materials

Stiffness against density

Strength against density