Aluminum 1100-O vs. Stainless Steel 17-4PH

Compare Aluminum 1100-O vs. Stainless Steel 17-4PH strength, stiffness, weight and thermal properties.

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Mechanical
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Yield strength	35MPasourcetypical, O, 0.0625 in specimen	1,275MPasourcetypical, transverse, sheet/strip
Ultimate tensile strength	90MPasourcetypical, O	1,379MPasourcetypical, transverse, sheet/strip
Elongation at break	35%sourcetypical, O, in 4D	9%sourcetypical, transverse, in 2 in. (50.8 mm)
Young's modulus (stiffness)	69GPasourcetypical	197GPasourceH 900
Density	2,710kg/m³sourcenominal, 20 °C	7,800kg/m³sourceH 900
Strength to weight	12.9kN·m/kg	163kN·m/kg12.7x higher
Stiffness to weight	25.5MN·m/kg	25.3MN·m/kg
Poisson's ratio	not sourced	0.272sourceH 900 (column)
Shear modulus	not sourced	77.4GPa
Bulk modulus	not sourced	144GPa
Speed of sound	5,046m/s	5,026m/s
Thermal
Thermal conductivity	222W/m·Ksourcetypical, O, 20 °C	17.9W/m·Ksourceat 149 °C (300 °F), H 900
Thermal expansion	23.6µm/m·Ksourcetypical, mean 20-100 °C	10.8µm/m·Ksourcemean, 21–93 °C (70–200 °F), H 900
100 mm part over a 50 °C swing	118µm growth	54µm growth2.19x less
Specific heat	901J/kg·Ksourcebase material: commercially pure aluminium EN AW-1050A (Hydro), 20 °C	460J/kg·Ksourcemean, 0–100 °C, H 900
Heats up and cools (diffusivity)	90.9mm²/s18.2x faster	4.99mm²/s
Thermal shock resistance	not sourced	7,809W/m
Melting point	640–655°Csourcemelting range	not sourced
Max service temperature	not sourced	316°Csourcestrength-retention limit (not oxidation)
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).	Cleveland-Cliffs 17-4 PH, Condition H 900, sheet/strip, transverse (Product Data Bulletin, May 2021)

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 17-4PH?

Stainless Steel 17-4PH is stronger: its yield strength is 1,275 MPa against 35 MPa for Aluminum 1100-O (36.4x).

Which is lighter, Aluminum 1100-O or Stainless Steel 17-4PH?

Aluminum 1100-O is lighter: 2,710 kg/m³ against 7,800 kg/m³ for Stainless Steel 17-4PH.

Which is stiffer, Aluminum 1100-O or Stainless Steel 17-4PH?

Stainless Steel 17-4PH is stiffer: Young's modulus 197 GPa against 69 GPa for Aluminum 1100-O, so the same part in Stainless Steel 17-4PH deflects less under the same load.

Which is lighter for the same job, Aluminum 1100-O or Stainless Steel 17-4PH?

For the same stiffness or strength: Aluminum 1100-O is lighter for a stiff beam (bending), stiff panel or plate; Stainless Steel 17-4PH is lighter for a strong rod or tie, strong beam, strong panel or plate.

Part that must be	Aluminum 1100-O	Stainless Steel 17-4PH
Stiff rod or tie (tension)	about equal	about equal
Stiff beam (bending)	lighter	1.7x heavier
Stiff panel or plate	lighter	2.03x heavier
Strong rod or tie	12.7x heavier	lighter
Strong beam	3.82x heavier	lighter
Strong panel or plate	2.1x 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).

Which conducts heat better, Aluminum 1100-O or Stainless Steel 17-4PH?

Aluminum 1100-O conducts heat better: 222 W/m·K against 17.9 W/m·K for Stainless Steel 17-4PH.

Which expands less with temperature?

Stainless Steel 17-4PH expands less: 10.8 µm/m·K against 23.6 µm/m·K for Aluminum 1100-O.

Among 72 materials

Stiffness against density

Strength against density