Magnesium AZ31B-H24 vs. Silicon

Compare Magnesium AZ31B-H24 vs. Silicon strength, stiffness, weight and thermal properties.

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SiliconGrown single crystal

Mechanical
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Yield strength	220MPasourcetypical, H24, 0.5-6 mm, 0.2 % proof stress	not given (tensile used)
Ultimate tensile strength	290MPasourcetypical, H24, 0.5-6 mm	130MPasourcemodulus of rupture (bending fracture stress); brittle, no yield point
Flexural strength	not sourced	130MPasourcemodulus of rupture
Elongation at break	13%sourcetypical, H24, 0.5-6 mm, gauge 5.65√A	not sourced
Young's modulus (stiffness)	44.8GPasourcetypical (handbook physical constant)	131GPasourcetypical (single quoted value of an anisotropic crystal)
Density	1,769kg/m³sourcenominal	2,329kg/m³sourcetypical
Strength to weight	124kN·m/kg2.23x higher	55.8kN·m/kg
Stiffness to weight	25.3MN·m/kg	56.2MN·m/kg2.22x higher
Poisson's ratio	0.35sourcetypical (handbook physical constant)	0.221sourcetypical
Shear modulus	16.6GPa	53.6GPa3.23x stiffer in shear
Bulk modulus	49.8GPa	78.3GPa
Speed of sound	5,032m/s	7,500m/s
Thermal
Thermal conductivity	76.9W/m·Ksourcetypical (temper/temperature not stated)	163W/m·Ksourcetypical at 313 K (40 °C)
Thermal expansion	26.8µm/m·Ksourcetypical (temperature range not stated)	2.62µm/m·Ksourcetypical at 300 K
100 mm part over a 50 °C swing	134µm growth	13.1µm growth10.2x less
Specific heat	1,040J/kg·Ksourcetypical	732J/kg·Ksourcetypical
Heats up and cools (diffusivity)	41.8mm²/s	95.6mm²/s2.29x faster
Thermal shock resistance	9,159W/m	48,095W/m5.25x more resistant
Melting point	not sourced	1,412°Csourcetypical
Max service temperature	149°Csourcestated application limit	300°Csourceproducer's maximum application temperature (optical components)
Values for	AZ31B-H24 sheet 0.016-0.062 in., MIL-HDBK-5J Table 4.2.1.0(b) (AMS 4377); strengths are S-basis MINIMUMS	Synthetic single-crystal silicon (cubic, diamond structure), Korth Kristalle (crystal grower) material data; Korth usually supplies Floating Zone (FZ) material, Czochralski (Cz) also offered. Silicon is elastically anisotropic; the producer quotes one modulus and the solver is isotropic.

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 AZ31B-H24 stronger than Silicon?

Magnesium AZ31B-H24 is stronger: its yield strength is 220 MPa against tensile strength 130 MPa for Silicon (1.69x).

Which is lighter, Magnesium AZ31B-H24 or Silicon?

Magnesium AZ31B-H24 is lighter: 1,769 kg/m³ against 2,329 kg/m³ for Silicon.

Which is stiffer, Magnesium AZ31B-H24 or Silicon?

Silicon is stiffer: Young's modulus 131 GPa against 44.8 GPa for Magnesium AZ31B-H24, so the same part in Silicon deflects less under the same load.

Which is lighter for the same job, Magnesium AZ31B-H24 or Silicon?

For the same stiffness or strength: Magnesium AZ31B-H24 is lighter for a strong rod or tie, strong beam, strong panel or plate; Silicon is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate.

Part that must be	Magnesium AZ31B-H24	Silicon
Stiff rod or tie (tension)	2.22x heavier	lighter
Stiff beam (bending)	30% heavier	lighter
Stiff panel or plate	9% heavier	lighter
Strong rod or tie	lighter	2.23x heavier
Strong beam	lighter	1.87x heavier
Strong panel or plate	lighter	1.71x 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 conducts heat better, Magnesium AZ31B-H24 or Silicon?

Silicon conducts heat better: 163 W/m·K against 76.9 W/m·K for Magnesium AZ31B-H24.

Which expands less with temperature?

Silicon expands less: 2.62 µm/m·K against 26.8 µm/m·K for Magnesium AZ31B-H24.

Among 72 materials

Stiffness against density

Strength against density