Jul 5 2013
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
Machinability
Forming
Welding
Annealing
Hot Working
Cold Working
Applications
Introduction
Titanium alloys are formed when titanium is combined with other alloying metals such as manganese, aluminum, zirconium, tin and molybdenum.
Grade Ti 8 Mn alloy is an alpha-beta wrought alloy. This alloy is heat treatable and combines superior strength to weight ratio with good corrosion resistance and fabricability.
The following sections will discuss in detail about grade Ti 8 Mn alloy.
Chemical Composition
The chemical composition of grade Ti 8 Mn alloy is outlined in the following table.
|
Element |
Content (%) |
|
Titanium, Ti |
92 |
|
Manganese, Mn |
8 |
|
Oxygen, O |
≤ 0.20 |
|
Carbon, C |
≤ 0.20 |
|
Nitrogen, N |
≤ 0.070 |
|
Hydrogen, H |
≤ 0.015 |
Physical Properties
The physical properties of grade Ti 8 Mn alloy are tabulated below.
|
Properties |
Metric |
Imperial |
|
Density |
4.73 g/cm3 |
0.171 lb/in3 |
|
Melting point |
1565°C |
2849°F |
Mechanical Properties
The following table shows mechanical properties of grade Ti 8 Mn alloy.
|
Properties |
Metric |
Imperial |
|
Tensile strength |
900 MPa |
131000 psi |
|
Yield strength |
810 MPa |
117000 psi |
|
Poisson’s ratio |
0.33 |
0.33 |
|
Elastic modulus |
115 GPa |
16700 ksi |
|
Shear modulus |
43.2 GPa |
6270 ksi |
|
Elongation at break |
14% |
14% |
|
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 8 Mn 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 |
10.9 W/mK |
75.6 BTU in/hr.ft².°F |
Other Designations
Equivalent materials to grade Ti 8 Mn alloy are as follows:
Fabrication and Heat Treatment
Machinability
Grade Ti 8 Mn 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 8 Mn alloy can be hot or cold formed using hydropress, stretch or drop hammer methods.
Welding
Welding of grade Ti 8 Mn alloy should be avoided.
Annealing
Full annealing of grade Ti 8 Mn alloy can be performed by holding the material at 680°C (1250°F) for 1 h, furnace cooling to 490°C (900°F), and finally air cooling.
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 8 Mn alloy is mainly used in aircraft and structural parts.