Jul 24 2013
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Fabrication and Heat Treatment
Machinability
Forming
Hot Working
Cold Working
Applications
Introduction
Titanium alloys possess excellent corrosion resistance, very high tensile strength and toughness. Another added advantage is that they are light weight.
Grade Ti 7AI 4Mo alloy is an alpha-beta alloy that has high strength and good creep resistance.The following sections will discuss in detail about grade Ti 7AI 4Mo alloy.
Chemical Composition
The chemical composition of grade Ti 7AI 4Mo alloy is outlined in the following table.
|
Element |
Content (%) |
|
Titanium, Ti |
89 |
|
Aluminum, Al |
7 |
|
Molybdenum, Mo |
4 |
|
Iron, Fe |
≤ 0.30 |
|
Oxygen, O |
≤ 0.20 |
|
Carbon, C |
≤ 0.10 |
|
Nitrogen, N |
≤ 0.050 |
|
Hydrogen, H |
≤ 0.013 |
Physical Properties
The physical properties of grade Ti 7AI 4Mo alloy are tabulated below.
|
Properties |
Metric |
Imperial |
|
Density |
4.48 g/cm3 |
0.162 lb/in3 |
|
Melting point |
≤ 1650°C |
≤ 3000°F |
Mechanical Properties
The following table shows mechanical properties of grade Ti 7AI 4Mo alloy.
|
Properties |
Metric |
Imperial |
|
Tensile strength |
1030 MPa |
149000 psi |
|
Yield strength |
970 MPa |
141000 psi |
|
Poisson’s ratio |
0.32 |
0.32 |
|
Elastic modulus |
111 GPa |
16100 ksi |
|
Shear modulus |
42 GPa |
6090 ksi |
|
Hardness, Brinell |
318 |
318 |
|
Hardness, Knoop |
346 |
346 |
|
Hardness, Rockwell C |
34 |
34 |
|
Hardness, Vickers |
333 |
333 |
Thermal Properties
The thermal properties of grade Ti 7AI 4Mo alloy are tabulated below.
|
Properties |
Metric |
Imperial |
|
Thermal expansion co-efficient (@0.000-100°C/32-212°F) |
9 µm/m°C |
5 µin/in°F |
|
Thermal conductivity |
6.10 W/mK |
42.3 BTU in/hr.ft².°F |
Fabrication and Heat Treatment
Machinability
Grade Ti 7AI 4Mo alloy is hard to machine but can be successfully done using slow speeds, high coolant flow, and high feed rates. Tooling should be performed using tungsten carbide designations C1-C4 or cobalt type high speed tools.
Forming
Grade Ti 7AI 4Mo alloy can be hot or cold formed using power brake, hydropress, stretch or drop hammer methods.
Hot Working
Hot working enhances the overall ductility of the material.
Cold Working
Cold working features of this material is same as that of a moderately tempered austenitic stainless steel. Post-work annealing is recommended to re-attain favorable performance properties.
Applications
Grade Ti 7AI 4Mo alloy is used in the following application areas:
-
Structural components in aerospace
-
Jet engine disks
-
Compressor blades and spacers
-
Sonic horns