Thermal conductivity against densityHigher and further left: spreads more heat for its weightThermal expansion against thermal conductivityLower and further right: warps less when heated
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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.
Silicon
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.
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NA Alloys Product DataDaiki Aluminium IndustryAluminum ADC12 · Yield strength: one test result, 0.2% proof stress, as cast, ASTM tensile bar (Daiki)Aluminum ADC12 · Ultimate tensile strength: one test result, as cast, ASTM tensile bar (Daiki)Aluminum ADC12 · Elongation at break: one test result, as cast, ASTM tensile bar (Daiki)
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Si: SiliconKorth Kristallearchived copySilicon · Ultimate tensile strength: modulus of rupture (bending fracture stress); brittle, no yield pointSilicon · Flexural strength: modulus of ruptureSilicon · Young's modulus (stiffness): typical (single quoted value of an anisotropic crystal)Silicon · Density: typicalSilicon · Poisson's ratio: typicalSilicon · Thermal conductivity: typical at 313 K (40 °C)Silicon · Thermal expansion: typical at 300 KSilicon · Specific heat: typicalSilicon · Melting point: typicalSilicon · Max service temperature: producer's maximum application temperature (optical components)
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Die-Casting Alloys (ダイカスト用合金)S.S. AluminumAluminum ADC12 · Young's modulus (stiffness): standard value (S.S.Aluminum)
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DIK365 Product DataDaiki Aluminium IndustryAluminum ADC12 · Density: measured (Daiki)Aluminum ADC12 · Thermal conductivity: measured on specimens cut from a 50 x 100 x 5 mm flat die casting (Daiki)Aluminum ADC12 · Thermal expansion: measured, temperature range not stated (Daiki)Aluminum ADC12 · Specific heat: measured (Daiki)Aluminum ADC12 · Melting point: solidus-liquidus (Daiki)
Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Mechanical
Is Aluminum ADC12 stronger than Silicon?
Aluminum ADC12 is stronger: its yield strength is 149 MPa against tensile strength 130 MPa for Silicon (15%).
Which is lighter, Aluminum ADC12 or Silicon?
Silicon is lighter: 2,329 kg/m³ against 2,680 kg/m³ for Aluminum ADC12.
Which is stiffer, Aluminum ADC12 or Silicon?
Silicon is stiffer: Young's modulus 131 GPa against 79.8 GPa for Aluminum ADC12, so the same part in Silicon deflects less under the same load.
Which is lighter for the same job, Aluminum ADC12 or Silicon?
For the same stiffness or strength: Silicon is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong beam, strong panel or plate.
Part that must be
Aluminum ADC12
Silicon
Stiff rod or tie (tension)
1.89x heavier
lighter
Stiff beam (bending)
47% heavier
lighter
Stiff panel or plate
36% heavier
lighter
Strong rod or tie
about equal
about equal
Strong beam
5% heavier
lighter
Strong panel or plate
7% 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).
Thermal
Which conducts heat better, Aluminum ADC12 or Silicon?
Silicon conducts heat better: 163 W/m·K against 125 W/m·K for Aluminum ADC12.
Which expands less with temperature?
Silicon expands less: 2.62 µm/m·K against 21 µm/m·K for Aluminum ADC12.