Grade 23 Ti 6Al 4V ELI Alloy (UNS R56401)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
     Machinability
     Forming
     Welding
     Heat Treatment
     Annealing
     Forging
     Hot Working
     Cold Working
     Aging
Applications

Introduction

Titanium alloys are divided into three main groups: alpha-phase, beta-phase, and alpha-beta-phase. Grade 23 Ti 6Al 4V ELI alloy is an alpha-beta wrought alloy. The ELI stands for extra low interstitial. For an alloy to be branded as an ELI product, it should be produced as such at the mill.

The following sections will discuss in detail about grade 23 Ti 6Al 4V ELI alloy.

Chemical Composition

The chemical composition of grade 23 Ti 6Al 4V ELI alloy is outlined in the following table.

Element Content (%)
Titanium, Ti 88.09 - 91
Aluminum, Al 5.5 - 6.5
Vanadium, V 3.5 - 4.5
Iron, Fe ≤ 0.25
Carbon, C ≤ 0.080
Nitrogen, N ≤ 0.030
Hydrogen, H ≤ 0.0125
Other, each ≤ 0.10
Other, total ≤ 0.40

Physical Properties

The physical properties of grade 23 Ti 6Al 4V ELI alloy are tabulated below.

Properties Metric Imperial
Density 4.43 g/cm3 0.160 lb/in3
Melting point 1604 - 1660°C 2919 - 3020°F

Mechanical Properties

The following table shows mechanical properties of grade 23 Ti 6Al 4V ELI alloy.

Properties Metric Imperial
Tensile strength 860 MPa 125000 psi
Yield strength 790 MPa 115000 psi
Poisson’s ratio 0.342 0.342
Elastic modulus 113.8 GPa 16510 ksi
Shear modulus 44.0 GPa 6380 ksi
Elongation at break 15% 15%
Hardness, Brinell 326 326
Hardness, Knoop 354 354
Hardness, Rockwell C 35 35
Hardness, Vickers 341 341

Thermal Properties

The thermal properties of grade 23 Ti 6Al 4V ELI alloy are tabulated below.

Properties Metric Imperial
Thermal expansion co-efficient (@20-100°C/68-212°F) 8.60 µm/m°C 4.78 µin/in°F
Thermal conductivity 6.70 W/mK 46.5 BTU in/hr.ft².°F

Other Designations

Equivalent materials to grade 23 Ti 6Al 4V ELI alloy are as follows:

  • AMS 4907
  • AMS 4931
  • ASTM F136
  • ASTM F467 (TI-5)
  • ASTM F468 (5)
  • ASTM F468 (S)
  • MIL F-83142
  • MIL T-9046
  • MIL T-9047
  • SPS M618
  • AMS 4930
  • AMS 4956

Fabrication and Heat Treatment

Machinability

Grade 23 Ti 6Al 4V ELI alloy can be machined using slow speeds, right quantity of coolant flow and high feed rates. High-speed tools should be used for tooling this alloy and the recommended tool types are tungsten carbide designations C1-C4 or cobalt based.

Forming

Grade 23 Ti 6Al 4V ELI alloy can be hot or cold formed. Forming techniques include hydropress, stretch or drop-hammer.

Welding

Weldability of grade 23 Ti 6Al 4V ELI alloy is rated as fair.

Heat Treatment

The material can be solution treated at 904-954 °C (1660-1750°F) for 2 h, and then water quenched.

Annealing

For annealing grade 23 Ti 6Al 4V ELI alloy, the material has to be held at 732°C (1350°F) for about 1/4 and 4h. It should then be furnace cooled to 566°C (1050°F) then air cooled.

Forging

Rough forging can be performed at 982°C (1800°F), and completed at 968°C (1750°F).

Hot Working

Hot working enhances the overall ductility of the material.

Cold Working

Cold working features of this material is same as that of austenitic stainless steel. Post-work annealing is recommended to re-attain favorable performance properties.

Aging

Aging of grade 23 Ti 6Al 4V ELI alloy can be performed at 538°C (1000°F) for 4 h and air cooled.

Applications

Grade 23 Ti 6Al 4V ELI alloy is used in the following areas:

  • Surgical implants
  • Aircraft components
  • Structural components
  • In a variety of salt water applications
  • In high pressure cryogenic vessels down to -320°C
  • In applications requiring excellent fracture toughness and fatigue strength.

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