Silicon vs. Steel AISI 1045

Compare Silicon vs. Steel AISI 1045 strength, stiffness, weight and thermal properties.

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SiliconGrown single crystal

Mechanical
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Yield strength	not given (tensile used)	531MPasourceproducer-stated, cold drawn
Ultimate tensile strength	130MPasourcemodulus of rupture (bending fracture stress); brittle, no yield point	627MPasourceproducer-stated, cold drawn
Flexural strength	130MPasourcemodulus of rupture	not sourced
Elongation at break	not sourced	12%sourcein 2 in (50.8 mm)
Young's modulus (stiffness)	131GPasourcetypical (single quoted value of an anisotropic crystal)	210GPasourcetypical
Density	2,329kg/m³sourcetypical3.35x lighter	7,800kg/m³sourcetypical
Strength to weight	55.8kN·m/kg	68.1kN·m/kg22% higher
Stiffness to weight	56.2MN·m/kg2.09x higher	26.9MN·m/kg
Poisson's ratio	0.221sourcetypical	0.3sourcetypical
Shear modulus	53.6GPa	80.8GPa1.51x stiffer in shear
Bulk modulus	78.3GPa	175GPa
Speed of sound	7,500m/s	5,189m/s
Thermal
Thermal conductivity	163W/m·Ksourcetypical at 313 K (40 °C)	40–45W/m·Ksourcetypical range, ambient
Thermal expansion	2.62µm/m·Ksourcetypical at 300 K	12µm/m·Ksourcetypical, mean 20-300 °C
100 mm part over a 50 °C swing	13.1µm growth4.58x less	60µm growth
Specific heat	732J/kg·Ksourcetypical	460–480J/kg·Ksourcetypical range, 50/100 °C
Heats up and cools (diffusivity)	95.6mm²/s8.25x faster	11.6mm²/s
Thermal shock resistance	48,095W/m7.67x more resistant	6,269W/m
Melting point	1,412°Csourcetypical	not sourced
Max service temperature	300°Csourceproducer's maximum application temperature (optical components)	not sourced
Values for	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.	AISI 1045 cold drawn bar (Niagara LaSalle) for mechanical; Ovako C45 (lists 'SAE 1045' as a similar designation) for physical constants

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 Silicon stronger than Steel AISI 1045?

Steel AISI 1045 is stronger: its yield strength is 531 MPa against tensile strength 130 MPa for Silicon (4.08x).

Which is lighter, Silicon or Steel AISI 1045?

Silicon is lighter: 2,329 kg/m³ against 7,800 kg/m³ for Steel AISI 1045.

Which is stiffer, Silicon or Steel AISI 1045?

Steel AISI 1045 is stiffer: Young's modulus 210 GPa against 131 GPa for Silicon, so the same part in Steel AISI 1045 deflects less under the same load.

Which is lighter for the same job, Silicon or Steel AISI 1045?

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; Steel AISI 1045 is lighter for a strong rod or tie.

Part that must be	Silicon	Steel AISI 1045
Stiff rod or tie (tension)	lighter	2.09x heavier
Stiff beam (bending)	lighter	2.65x heavier
Stiff panel or plate	lighter	2.86x heavier
Strong rod or tie	22% heavier	lighter
Strong beam	lighter	31% heavier
Strong panel or plate	lighter	1.66x 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, Silicon or Steel AISI 1045?

Silicon conducts heat better: 163 W/m·K against 42.5 W/m·K for Steel AISI 1045.

Which expands less with temperature?

Silicon expands less: 2.62 µm/m·K against 12 µm/m·K for Steel AISI 1045.

Among 72 materials

Stiffness against density

Strength against density