Jul 30 2013
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.