Jun 20 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 metals containing a blend of titanium and other chemical elements.
Grade 6Al 2Sn 4Zr 2Mo titanium alloy is a near alpha alloy. Near-alpha alloys contain a small amount of ductile beta-phase. It was developed to handle operations in high temperature applications of up to 538°C (°1000.4°F). This alloy has a combination of excellent strength and corrosion resistance with comparatively good weldabilty and fabricability.
The following sections will discuss in detail about grade 6Al 2Sn 4Zr 2Mo titanium alloy.
Chemical Composition
The chemical composition of grade 6Al 2Sn 4Zr 2Mo titanium alloy is outlined in the following table.
|
Element |
Content (%) |
|
Titanium, Ti |
83.785 - 87.24 |
|
Aluminum, Al |
5.5 - 6.5 |
|
Zirconium, Zr |
3.6 - 4.4 |
|
Tin, Sn |
1.8 - 2.2 |
|
Molybdenum, Mo |
1.8 - 2.2 |
|
Iron, Fe |
≤ 0.25 |
|
Oxygen, O |
≤ 0.15 |
|
Silicon, Si |
0.060 - 0.10 |
|
Carbon, C |
≤ 0.050 |
|
Nitrogen, N |
≤ 0.050 |
|
Hydrogen, H |
≤ 0.015 |
|
Other, each |
≤ 0.10 |
|
Other, total |
≤ 0.30 |
Physical Properties
The physical properties of grade 6Al 2Sn 4Zr 2Mo titanium alloy are tabulated below.
|
Properties |
Metric |
Imperial |
|
Density |
4.54 g/cm3 |
0.164 lb/in3 |
|
Melting point |
≤ 1705°C |
≤ 3101°F |
Mechanical Properties
The following table shows mechanical properties of grade 6Al 2Sn 4Zr 2Mo titanium alloy.
|
Properties |
Metric |
Imperial |
|
Tensile strength |
1110 MPa |
161000 psi |
|
Yield strength |
1050 MPa |
152000 psi |
|
Poisson’s ratio |
0.325 |
0.325 |
|
Elastic modulus |
118 GPa |
17100 ksi |
|
Shear modulus |
44.5 GPa |
6450 ksi |
|
Elongation at break |
13% |
13% |
|
Hardness, Brinell |
318 |
318 |
|
Hardness, Knoop |
346 |
346 |
|
Hardness, Rockwell C |
34 |
34 |
|
Hardness, Vickers |
333 |
333 |
Thermal Properties
The thermal properties of grade 6Al 2Sn 4Zr 2Mo titanium alloy are tabulated below.
|
Properties |
Metric |
Imperial |
|
Thermal expansion co-efficient (@0.000-100°C/32-212°F) |
7.70 µm/m°C |
4.28 µin/in°F |
|
Thermal conductivity |
7 W/mK |
48.6 BTU in/hr.ft².°F |
Other Designations
Equivalent materials to grade 6Al 2Sn 4Zr 2Mo titanium alloy are as follows:
|
MIL-T-9046 |
MIL T-9046 |
MIL F-83142 |
PWA 1220 |
|
AMS 4919 |
GE B50 TF22 |
GE B50TF21 |
MIL T-81915 |
|
AMS 4975 |
AMS 4976 |
GE C50TF7 |
MIL T-9047 |
AMS 4952
|
DIN 3.7164
|
GE B50TF22
|
|
Fabrication and Heat Treatment
Machinability
Although tough, grade 6Al 2Sn 4Zr 2Mo 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 6Al 2Sn 4Zr 2Mo titanium alloy can be hot or cold formed.
Welding
Weldabilty of grade 6 Ti-5Al-2.5Sn alloy is rated as fair.
Heat Treatment
Recommended heat treatment is Beta minus 14C (25 F).
Annealing
Duplex annealing of this material can be performed by holding at 900°C (1670° F) for 1/2 h, air cooling to 788°C (1465°F) and again air cooled. In case of beta annealing, the process requires holding at 1024°C (1900°F) for 1/2 h, air cooling to 593°C (1100°F) for 8 h and finally air cooled.
Forging
Rough forging can be performed at 1038-1066°C (1929-1980°F) and completed at 954-982°C (1770-1825°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 6Al 2Sn 4Zr 2Mo titanium alloy can be performed by holding the material at 538-593 °C (1000-1100 °F) for 8 h and then air cooling.
Applications
Grade 6Al 2Sn 4Zr 2Mo titanium alloy is used in the following application areas:
-
Sheet metal parts in afterburners and hot airframe sections
-
Gas turbine compressor components e.g. discs, blades, and impellers.