Aluminum 7075-T6 vs. Stainless Steel 303

Compare Aluminum 7075-T6 vs. Stainless Steel 303 strength, stiffness, weight and thermal properties.

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Mechanical
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Yield strength	503MPasourcetypical, 0.2% offset, .500 in dia specimen	275MPasourceOutokumpu typical (product P = hot rolled plate, transverse)
Ultimate tensile strength	572MPasourcetypical	585MPasourceOutokumpu typical
Elongation at break	11%sourcetypical, in 4D	35%sourceOutokumpu typical, A5
Young's modulus (stiffness)	71GPasourcetypical	200GPasourceat RT (Table 12)
Density	2,800kg/m³sourcenominal	7,900kg/m³sourceat RT
Strength to weight	180kN·m/kg5.16x higher	34.8kN·m/kg
Stiffness to weight	25.4MN·m/kg	25.3MN·m/kg
Poisson's ratio	0.33sourcetypical (handbook physical constant)	0.3sourcedesign value (structural stainless steels)
Shear modulus	26.7GPa	76.9GPa2.88x stiffer in shear
Bulk modulus	69.6GPa	167GPa
Speed of sound	5,036m/s	5,032m/s
Thermal
Thermal conductivity	130W/m·Ksourcetypical, 20 °C, T651	15W/m·Ksourceat RT
Thermal expansion	23.4µm/m·Ksourcetypical, mean 20-100 °C	16µm/m·Ksourcemean, 20–100 °C
100 mm part over a 50 °C swing	117µm growth	80µm growth46% less
Specific heat	960J/kg·Ksourcetypical, at 100 °C	500J/kg·Ksourceat RT
Heats up and cools (diffusivity)	48.4mm²/s12.7x faster	3.8mm²/s
Thermal shock resistance	26,370W/m29.2x more resistant	902W/m
Melting point	532–635°Csourcemelting range	not sourced
Max service temperature	not sourced	871°Csourcecontinuous, scaling limit
Values for	7075-T6/T651, Kaiser Aluminum rod & bar (mechanical) and sheet/coil/plate (physical) typical datasheets; Poisson from MIL-HDBK-5J	1.4305 / UNS S30300, Outokumpu typical values (hot rolled, solution annealed) from 'Steel Grades, Properties and Global Standards'; max service from Carpenter CarTech 303 datasheet

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 7075-T6 stronger than Stainless Steel 303?

Aluminum 7075-T6 is stronger: its yield strength is 503 MPa against 275 MPa for Stainless Steel 303 (1.83x).

Which is lighter, Aluminum 7075-T6 or Stainless Steel 303?

Aluminum 7075-T6 is lighter: 2,800 kg/m³ against 7,900 kg/m³ for Stainless Steel 303.

Which is stiffer, Aluminum 7075-T6 or Stainless Steel 303?

Stainless Steel 303 is stiffer: Young's modulus 200 GPa against 71 GPa for Aluminum 7075-T6, so the same part in Stainless Steel 303 deflects less under the same load.

Which is lighter for the same job, Aluminum 7075-T6 or Stainless Steel 303?

For the same stiffness or strength: Aluminum 7075-T6 is lighter for a stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.

Part that must be	Aluminum 7075-T6	Stainless Steel 303
Stiff rod or tie (tension)	about equal	about equal
Stiff beam (bending)	lighter	1.68x heavier
Stiff panel or plate	lighter	2x heavier
Strong rod or tie	lighter	5.16x heavier
Strong beam	lighter	4.22x heavier
Strong panel or plate	lighter	3.82x 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 7075-T6 or Stainless Steel 303?

Aluminum 7075-T6 conducts heat better: 130 W/m·K against 15 W/m·K for Stainless Steel 303.

Which expands less with temperature?

Stainless Steel 303 expands less: 16 µm/m·K against 23.4 µm/m·K for Aluminum 7075-T6.

Among 72 materials

Stiffness against density

Strength against density