300°Csourceproducer's maximum application temperature (optical components)
Values for
6061-T6/T651, Kaiser Aluminum typical properties (sheet, coil & plate datasheet); 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 stronger than Silicon?
Aluminum is stronger: its yield strength is 276 MPa against tensile strength 130 MPa for Silicon (2.12x).
Which is lighter, Aluminum or Silicon?
Silicon is lighter: 2,329 kg/m³ against 2,700 kg/m³ for Aluminum.
Which is stiffer, Aluminum or Silicon?
Silicon is stiffer: Young's modulus 131 GPa against 68.3 GPa for Aluminum, so the same part in Silicon deflects less under the same load.
Which is lighter for the same job, Aluminum or Silicon?
For the same stiffness or strength: Aluminum 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
Silicon
Stiff rod or tie (tension)
2.22x heavier
lighter
Stiff beam (bending)
1.61x heavier
lighter
Stiff panel or plate
44% heavier
lighter
Strong rod or tie
lighter
1.83x heavier
Strong beam
lighter
42% heavier
Strong panel or plate
lighter
26% 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 or Silicon?
Aluminum conducts heat better: 167 W/m·K against 163 W/m·K for Silicon.
Which expands less with temperature?
Silicon expands less: 2.62 µm/m·K against 23.6 µm/m·K for Aluminum.