Aluminum 1100-O vs. Stainless Steel 303

Compare Aluminum 1100-O vs. Stainless Steel 303 strength, stiffness, weight and thermal properties.

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Mechanical
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Yield strength	35MPasourcetypical, O, 0.0625 in specimen	275MPasourceOutokumpu typical (product P = hot rolled plate, transverse)
Ultimate tensile strength	90MPasourcetypical, O	585MPasourceOutokumpu typical
Elongation at break	35%sourcetypical, O, in 4D	35%sourceOutokumpu typical, A5
Young's modulus (stiffness)	69GPasourcetypical	200GPasourceat RT (Table 12)
Density	2,710kg/m³sourcenominal, 20 °C	7,900kg/m³sourceat RT
Strength to weight	12.9kN·m/kg	34.8kN·m/kg2.7x higher
Stiffness to weight	25.5MN·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	5,046m/s	5,032m/s
Thermal
Thermal conductivity	222W/m·Ksourcetypical, O, 20 °C	15W/m·Ksourceat RT
Thermal expansion	23.6µm/m·Ksourcetypical, mean 20-100 °C	16µm/m·Ksourcemean, 20–100 °C
100 mm part over a 50 °C swing	118µm growth	80µm growth48% less
Specific heat	901J/kg·Ksourcebase material: commercially pure aluminium EN AW-1050A (Hydro), 20 °C	500J/kg·Ksourceat RT
Heats up and cools (diffusivity)	90.9mm²/s23.9x faster	3.8mm²/s
Thermal shock resistance	not sourced	902W/m
Melting point	640–655°Csourcemelting range	not sourced
Max service temperature	not sourced	871°Csourcecontinuous, scaling limit
Values for	1100-O (annealed) commercially pure aluminium, Kaiser Aluminum Tube & Pipe Alloy 1100 Technical Data (Rev. 05/06), typical properties; specific heat from Hydro EN AW-1050A (99.5% Al) extruded-products datasheet (10/2018).	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 1100-O stronger than Stainless Steel 303?

Stainless Steel 303 is stronger: its yield strength is 275 MPa against 35 MPa for Aluminum 1100-O (7.86x).

Which is lighter, Aluminum 1100-O or Stainless Steel 303?

Aluminum 1100-O is lighter: 2,710 kg/m³ against 7,900 kg/m³ for Stainless Steel 303.

Which is stiffer, Aluminum 1100-O or Stainless Steel 303?

Stainless Steel 303 is stiffer: Young's modulus 200 GPa against 69 GPa for Aluminum 1100-O, so the same part in Stainless Steel 303 deflects less under the same load.

Which is lighter for the same job, Aluminum 1100-O or Stainless Steel 303?

For the same stiffness or strength: Aluminum 1100-O is lighter for a stiff beam (bending), stiff panel or plate, strong panel or plate; Stainless Steel 303 is lighter for a strong rod or tie, strong beam.

Part that must be	Aluminum 1100-O	Stainless Steel 303
Stiff rod or tie (tension)	about equal	about equal
Stiff beam (bending)	lighter	1.71x heavier
Stiff panel or plate	lighter	2.04x heavier
Strong rod or tie	2.7x heavier	lighter
Strong beam	36% heavier	lighter
Strong panel or plate	lighter	4% 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 1100-O or Stainless Steel 303?

Aluminum 1100-O conducts heat better: 222 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 23.6 µm/m·K for Aluminum 1100-O.

Among 72 materials

Stiffness against density

Strength against density