Jul 8 2013
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
Machinability
Forming
Welding
Annealing
Forging
Hot Working
Cold Working
Applications
Introduction
Titanium alloys contain titanium and other chemical elements such as molybdenum, aluminum, vanadium, and iron.
Grade 8 Al 1Mo 1V titanium alloy is a near alpha alloy. This grade has high stiffness/density ratio, high modulus, low density, good elevated temperature tensile properties, medium to high strength, and excellent creep resistance to enable operating temperatures of up to 455°C (851°F).
The following sections will discuss in detail about grade 8 Al 1Mo 1V titanium alloy.
Chemical Composition
The chemical composition of grade 8 Al 1Mo 1V titanium alloy is outlined in the following table.
|
Element |
Content (%) |
|
Aluminum, Al |
7.35 - 8.35 |
|
Vanadium, V |
0.75 - 1.25 |
|
Molybdenum, Mo |
0.75 - 1.25 |
|
Iron, Fe |
0.3 max |
|
Oxygen, O |
0.12 max |
|
Carbon, C |
0.08 max |
|
Nitrogen, N |
0.05 max |
|
Hydrogen, H |
0.0125 max |
|
Titanium, Ti |
Remainder |
Physical Properties
The physical properties of grade 8 Al 1Mo 1V titanium alloy are tabulated below.
|
Properties |
Metric |
Imperial |
|
Density |
4.37 g/cm3 |
0.158 lb/in3 |
|
Melting point |
≤ 1540°C |
≤ 2800°F |
Mechanical Properties
The following table shows mechanical properties of grade 8 Al 1Mo 1V titanium alloy.
|
Properties |
Metric |
Imperial |
|
Tensile strength |
937 MPa |
136000 psi |
|
Yield strength |
910 MPa |
132000 psi |
|
Poisson’s ratio |
0.32 |
0.32 |
|
Elastic modulus |
120 GPa |
17400 ksi |
|
Shear modulus |
46 GPa |
6670 ksi |
|
Elongation at break |
18% |
18% |
|
Hardness, Brinell |
334 |
334 |
|
Hardness, Knoop |
363 |
363 |
|
Hardness, Rockwell C |
36 |
36 |
|
Hardness, Vickers |
349 |
349 |
Thermal Properties
The thermal properties of grade 8 Al 1Mo 1V titanium alloy are tabulated below.
|
Properties |
Metric |
Imperial |
|
Thermal expansion co-efficient (@0.000-100°C/32-212°F) |
8.50 µm/m°C |
4.72 µin/in°F |
|
Thermal conductivity |
6 W/mK |
41.6 BTU in/hr.ft².°F |
Other Designations
Equivalent materials to grade 8 Al 1Mo 1V titanium alloy are as follows:
-
AMS 4915
-
AMS 4916
-
AMS 4933
-
AMS 4955
-
AMS 4972
-
AMS 4973
-
MIL F-83142
-
MIL T-81556
-
MIL T-9046
-
MIL T-9047
Fabrication and Heat Treatment
Machinability
Although tough, grade 8 Al 1Mo 1V titanium alloy can be machined using the right quantity of coolant flow, slow speeds 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 8 Al 1Mo 1V titanium alloy can be hot or cold formed using hydropress, stretch or drop-hammer methods.
Welding
Weldabilty of grade 8 Al 1Mo 1V titanium alloy is rated as fair.
Annealing
Annealing of this material requires single-hold at 738°C (1450° F) for 8 h, followed by furnace cooling. Duplex single annealing is performed by heating to 788°C (1450 °F) for 1/4 h and air cooled. Stress relief annealing requires the material to be held at 593-649°C (1100-1200 °F) for 1 h and air cooled.
Forging
Rough forging can be performed at 1010-1038°C (1850-1980°F) and completed at 1010°C (1850°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.
Applications
Grade 8 Al 1Mo 1V titanium alloy is used in the following application areas:
-
In jet engine components such as forged fan and compressor blades.
-
Industrial components such as discs, spacers, seals, rings, etc.