Drawing No. EH–MT–002 // Engineering Materials
AISI 4140 Alloy Steel Properties
Reviewed August 2026
AISI 4140 is a chromium-molybdenum low-alloy steel. This reference is tied to one explicit oil-quench and temper condition so the strength values are not confused with annealed, normalized or differently tempered 4140.
Representative properties
The stated basis, temperature and direction are part of the value. Switch units without changing the physical reference.
What changes these properties?
Engineering variability
- Yield and tensile strength vary strongly with tempering temperature and section size.
- The displayed elastic modulus is a typical steel value in the selected dataset; it is much less heat-treatment-sensitive than strength.
- Specific heat in the source is tabulated at 150–200°C rather than room temperature and is labeled accordingly.
- Final design should use the actual product specification, heat treatment, hardness and mill test data.
Selection note
Widely used for shafts, gears, bolts, tooling and machinery parts needing higher hardenability and strength than plain-carbon steel.
Where a property is shown as qualitative rather than numeric, that is intentional: the selected source or the material physics does not justify a single comparable scalar.
How to interpret this material
Stiffness
Young’s modulus describes elastic stiffness. For crystals and composites, orientation can make one scalar modulus only a directional reference.
Strength / failure
Ductile metals can use yield and tensile strength. Brittle ceramics/semiconductors and anisotropic composites require fracture, flexural or directional strength descriptions instead.
Thermal response
Conductivity, heat capacity and expansion are temperature dependent. The last column is a melting or transition descriptor only where that physical concept is appropriate.
Technical sources
The database favors manufacturer, industry, government or academic technical references and labels secondary condition-specific datasets when a primary source does not expose a complete property set.