Aluminum 7050-T7451 vs. Silicon

Compare Aluminum 7050-T7451 vs. Silicon strength, stiffness, weight and thermal properties.

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SiliconGrown single crystal

Mechanical
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Yield strength	469MPasourcetypical, longitudinal, 0.2% offset	not given (tensile used)
Ultimate tensile strength	524MPasourcetypical, longitudinal	130MPasourcemodulus of rupture (bending fracture stress); brittle, no yield point
Flexural strength	not sourced	130MPasourcemodulus of rupture
Elongation at break	11%sourcetypical, longitudinal	not sourced
Young's modulus (stiffness)	70.3GPasourcetypical	131GPasourcetypical (single quoted value of an anisotropic crystal)
Density	2,830kg/m³sourcenominal	2,329kg/m³sourcetypical
Strength to weight	166kN·m/kg2.97x higher	55.8kN·m/kg
Stiffness to weight	24.8MN·m/kg	56.2MN·m/kg2.26x higher
Poisson's ratio	0.33sourcetypical (handbook physical constant)	0.221sourcetypical
Shear modulus	26.4GPa	53.6GPa2.03x stiffer in shear
Bulk modulus	68.9GPa	78.3GPa
Speed of sound	4,984m/s	7,500m/s
Thermal
Thermal conductivity	157W/m·Ksourcetypical, 20 °C	163W/m·Ksourcetypical at 313 K (40 °C)
Thermal expansion	23.5µm/m·Ksourcetypical, mean 20-100 °C	2.62µm/m·Ksourcetypical at 300 K
100 mm part over a 50 °C swing	118µm growth	13.1µm growth8.97x less
Specific heat	860J/kg·Ksourcetypical, at 100 °C	732J/kg·Ksourcetypical
Heats up and cools (diffusivity)	64.5mm²/s	95.6mm²/s48% faster
Thermal shock resistance	29,862W/m	48,095W/m1.61x more resistant
Melting point	524–635°Csourcemelting range	1,412°Csourcetypical
Max service temperature	not sourced	300°Csourceproducer's maximum application temperature (optical components)
Values for	7050-T7451 plate, Kaiser Aluminum sheet, coil & plate typical datasheet (longitudinal); Poisson from MIL-HDBK-5J	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 Aluminum 7050-T7451 stronger than Silicon?

Aluminum 7050-T7451 is stronger: its yield strength is 469 MPa against tensile strength 130 MPa for Silicon (3.61x).

Which is lighter, Aluminum 7050-T7451 or Silicon?

Silicon is lighter: 2,329 kg/m³ against 2,830 kg/m³ for Aluminum 7050-T7451.

Which is stiffer, Aluminum 7050-T7451 or Silicon?

Silicon is stiffer: Young's modulus 131 GPa against 70.3 GPa for Aluminum 7050-T7451, so the same part in Silicon deflects less under the same load.

Which is lighter for the same job, Aluminum 7050-T7451 or Silicon?

For the same stiffness or strength: Aluminum 7050-T7451 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	Aluminum 7050-T7451	Silicon
Stiff rod or tie (tension)	2.26x heavier	lighter
Stiff beam (bending)	1.66x heavier	lighter
Stiff panel or plate	50% heavier	lighter
Strong rod or tie	lighter	2.97x heavier
Strong beam	lighter	1.94x heavier
Strong panel or plate	lighter	1.56x 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, Aluminum 7050-T7451 or Silicon?

Silicon conducts heat better: 163 W/m·K against 157 W/m·K for Aluminum 7050-T7451.

Which expands less with temperature?

Silicon expands less: 2.62 µm/m·K against 23.5 µm/m·K for Aluminum 7050-T7451.

Among 72 materials

Stiffness against density

Strength against density