Aug 9 2013
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
Machinability
Forming
Hot Working
Cold Working
Applications
Introduction
Titanium alloys possess very good corrosion resistance, high tensile strength and toughness. They are also light weight. Grade Ti 6Al 2Nb 1Ta 1Mo alloy is a near alpha wrought alloy.
Near-alpha alloys contain small amount of ductile beta-phase. Along with alpha-phase stabilizers, near-alpha alloys are alloyed with 1-2% of beta phase stabilizers such as silicon, molybdenum, or vanadium.
Grade Ti 6Al 2Nb 1Ta 1Mo alloy is known to possess high toughness, medium strength, weldability, and resistance to seawater corrosion. It is however not heat-treatable.
The following sections will discuss in detail about grade Ti 6Al 2Nb 1Ta 1Mo alloy.
Chemical Composition
The chemical composition of grade Ti 6Al 2Nb 1Ta 1Mo alloy is outlined in the following table.
|
Element |
Content (%) |
|
Aluminum, Al |
5.5 - 6.5 |
|
Niobium, Nb |
1.5 - 2.5 |
|
Tantalum, Ta |
0.5 - 1.5 |
|
Molybdenum, Mo |
0.5 - 1 |
|
Iron, Fe |
0.25 max |
|
Oxygen, O |
0.1 max |
|
Carbon, C |
0.05 max |
|
Nitrogen, N |
0.03 max |
|
Hydrogen, H |
0.0125 max |
|
Titanium, Ti |
Remainder |
Physical Properties
The physical properties of grade Ti 6Al 2Nb 1Ta 1Mo 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 6Al 2Nb 1Ta 1Mo alloy.
|
Properties |
Metric |
Imperial |
|
Tensile strength |
830 MPa |
120000 psi |
|
Yield strength |
730 MPa |
106000 psi |
|
Poisson’s ratio |
0.31 |
0.31 |
|
Elastic modulus |
113.8 GPa |
16510 ksi |
|
Shear modulus |
43.4 GPa |
6290 ksi |
|
Elongation at break |
13% |
13% |
|
Hardness, Brinell |
290 |
290 |
|
Hardness, Knoop |
315 |
315 |
|
Hardness, Rockwell C |
30 |
30 |
|
Hardness, Vickers |
304 |
304 |
Thermal Properties
The thermal properties of grade Ti 6Al 2Nb 1Ta 1Mo 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 |
6.40 W/mK |
44.4 BTU in/hr.ft².°F |
Other Designations
Equivalent material to grade Ti 6Al 2Nb 1Ta 1Mo alloy is MIL-T-9046.
Fabrication and Heat Treatment
Machinability
Grade Ti 6Al 2Nb 1Ta 1Mo 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 6Al 2Nb 1Ta 1Mo alloy can be hot or cold formed.
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 6Al 2Nb 1Ta 1Mo alloy is chiefly used in marine and sub-marine vehicles for their hardware and hull structures and in naval aircraft.