Aluminum 6063-T6 vs. Stainless Steel 303

Compare Aluminum 6063-T6 vs. Stainless Steel 303 strength, stiffness, weight and thermal properties.

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Mechanical
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Yield strength	215MPasourcetypical, T6, 0.0625 in specimen	275MPasourceOutokumpu typical (product P = hot rolled plate, transverse)
Ultimate tensile strength	240MPasourcetypical, T6	585MPasourceOutokumpu typical
Elongation at break	12%sourcetypical, T6, in 4D	35%sourceOutokumpu typical, A5
Young's modulus (stiffness)	69GPasourcetypical	200GPasourceat RT (Table 12)
Density	2,700kg/m³sourcenominal, 20 °C	7,900kg/m³sourceat RT
Strength to weight	79.6kN·m/kg2.29x higher	34.8kN·m/kg
Stiffness to weight	25.6MN·m/kg	25.3MN·m/kg
Poisson's ratio	not sourced	0.3sourcedesign value (structural stainless steels)
Shear modulus	not sourced	76.9GPa
Bulk modulus	not sourced	167GPa
Speed of sound	5,055m/s	5,032m/s
Thermal
Thermal conductivity	201W/m·Ksourcetypical, T6, 20 °C	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	901J/kg·Ksourcetypical, 20 °C (Hydro EN AW-6063)	500J/kg·Ksourceat RT
Heats up and cools (diffusivity)	82.6mm²/s21.8x faster	3.8mm²/s
Thermal shock resistance	not sourced	902W/m
Melting point	615–655°Csourcemelting range	not sourced
Max service temperature	not sourced	871°Csourcecontinuous, scaling limit
Values for	6063-T6 extruded tube, Kaiser Aluminum Tube & Pipe Alloy 6063 Technical Data (Rev. 05/06), typical properties; specific heat from Hydro EN AW-6063 extruded-products datasheet (Rev.4, 03/2023).	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 6063-T6 stronger than Stainless Steel 303?

Stainless Steel 303 is stronger: its yield strength is 275 MPa against 215 MPa for Aluminum 6063-T6 (28%).

Which is lighter, Aluminum 6063-T6 or Stainless Steel 303?

Aluminum 6063-T6 is lighter: 2,700 kg/m³ against 7,900 kg/m³ for Stainless Steel 303.

Which is stiffer, Aluminum 6063-T6 or Stainless Steel 303?

Stainless Steel 303 is stiffer: Young's modulus 200 GPa against 69 GPa for Aluminum 6063-T6, so the same part in Stainless Steel 303 deflects less under the same load.

Which is lighter for the same job, Aluminum 6063-T6 or Stainless Steel 303?

For the same stiffness or strength: Aluminum 6063-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 6063-T6	Stainless Steel 303
Stiff rod or tie (tension)	about equal	about equal
Stiff beam (bending)	lighter	1.72x heavier
Stiff panel or plate	lighter	2.05x heavier
Strong rod or tie	lighter	2.29x heavier
Strong beam	lighter	2.48x heavier
Strong panel or plate	lighter	2.59x 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 6063-T6 or Stainless Steel 303?

Aluminum 6063-T6 conducts heat better: 201 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 6063-T6.

Among 72 materials

Stiffness against density

Strength against density