Thermal conductivity against densityHigher and further left: spreads more heat for its weightThermal expansion against thermal conductivityLower and further right: warps less when heated
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TIMETAL 6-4 PropertiesTIMETarchived copyTitanium Ti-6Al-4V · Yield strength: typical, plate (>0.187 in), annealed, 0.2% offsetTitanium Ti-6Al-4V · Ultimate tensile strength: typical, plate, annealedTitanium Ti-6Al-4V · Elongation at break: typical, in 2 in., plate annealedTitanium Ti-6Al-4V · Density: nominalTitanium Ti-6Al-4V · Poisson's ratio: mean of TIMET measurementsTitanium Ti-6Al-4V · Melting point: melting rangeTitanium Ti-6Al-4V · Max service temperature: upper recommended use temperature
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MIL-HDBK-5J, Metallic Materials and Elements for Aerospace Vehicle Structures (2003)U.S. Department of DefenseSteel AISI 4340 · Young's modulus (stiffness): MIL-HDBK-5J design value (AISI 4340, quenched and tempered)Steel AISI 4340 · Poisson's ratio: MIL-HDBK-5J design value (AISI 4340, quenched and tempered)
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TIMETAL 6-4 Data SheetTIMETarchived copyTitanium Ti-6Al-4V · Young's modulus (stiffness): typical range, 20 °CTitanium Ti-6Al-4V · Thermal conductivity: typical, 20 °C, mill annealedTitanium Ti-6Al-4V · Thermal expansion: typical, mean 0-100 °CTitanium Ti-6Al-4V · Specific heat: typical, 20 °C
Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Mechanical
Is Steel AISI 4340 stronger than Titanium Ti-6Al-4V?
Steel AISI 4340 is stronger: its yield strength is 1,035 MPa against 885 MPa for Titanium Ti-6Al-4V (17%).
Which is lighter, Steel AISI 4340 or Titanium Ti-6Al-4V?
Titanium Ti-6Al-4V is lighter: 4,430 kg/m³ against 7,840 kg/m³ for Steel AISI 4340.
Which is stiffer, Steel AISI 4340 or Titanium Ti-6Al-4V?
Steel AISI 4340 is stiffer: Young's modulus 200 GPa against 115 GPa for Titanium Ti-6Al-4V, so the same part in Steel AISI 4340 deflects less under the same load.
Which is lighter for the same job, Steel AISI 4340 or Titanium Ti-6Al-4V?
For the same stiffness or strength: Titanium Ti-6Al-4V is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.
Part that must be
Steel AISI 4340
Titanium Ti-6Al-4V
Stiff rod or tie (tension)
1% heavier
lighter
Stiff beam (bending)
34% heavier
lighter
Stiff panel or plate
47% heavier
lighter
Strong rod or tie
1.51x heavier
lighter
Strong beam
1.59x heavier
lighter
Strong panel or plate
1.64x 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 is more ductile, Steel AISI 4340 or Titanium Ti-6Al-4V?
Steel AISI 4340 stretches further before it breaks: 18% elongation at break against 16% for Titanium Ti-6Al-4V.
Thermal
Which conducts heat better, Steel AISI 4340 or Titanium Ti-6Al-4V?
Steel AISI 4340 conducts heat better: 37.5 W/m·K against 6.6 W/m·K for Titanium Ti-6Al-4V.
Which expands less with temperature?
Titanium Ti-6Al-4V expands less: 9 µm/m·K against 11.3 µm/m·K for Steel AISI 4340.