Jun 20 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 are light weight and have excellent corrosion resistance, very high tensile strength and toughness. These properties remain unaffected to a great extent even at extreme temperatures. The durability of these alloys make them viable for several industries such as aerospace, military, automobile, consumer electronics, and sports equipment.
Grade 6 Ti-5Al-2.5Sn alloy has high service temperature of 480°C (896°F), medium strength, and excellent weldability and fabricability. This alloy has good oxidation resistance and microstructure stability; however it is not heat-treatable.
The following sections will discuss in detail about grade 6 Ti-5Al-2.5Sn alloy.
Chemical Composition
The chemical composition of grade 6 Ti-5Al-2.5Sn alloy is outlined in the following table.
|
Element |
Content (%) |
|
Titanium, Ti |
89.85 - 94 |
|
Aluminum, Al |
4-6 |
|
Tin, Sn |
2-3 |
|
Iron, Fe |
≤ 0.50 |
|
Oxygen, O |
≤ 0.20 |
|
Carbon, C |
≤ 0.10 |
|
Nitrogen, N |
≤ 0.030 |
|
Hydrogen, H |
≤ 0.015 |
|
Other, each |
≤ 0.050 |
|
Other, total |
≤ 0.30 |
Physical Properties
The physical properties of grade 6 Ti-5Al-2.5Sn alloy are tabulated below.
|
Properties |
Metric |
Imperial |
|
Density |
4.48 g/cm3 |
0.162 lb/in3 |
|
Melting point |
≤ 1590 °C |
≤ 2890 °F |
Mechanical Properties
The following table shows mechanical properties of grade 6 Ti-5Al-2.5Sn alloy.
|
Properties |
Metric |
Imperial |
|
Tensile strength |
517 MPa |
75000 psi |
|
Yield strength |
827 MPa |
120000 psi |
|
Elastic modulus |
110 - 125 GPa |
16000 - 18100 ksi |
|
Shear modulus |
48 GPa |
6960 ksi |
|
Elongation at break |
15% |
15% |
|
Hardness, Brinell |
320 |
320 |
|
Hardness, Knoop |
363 |
363 |
|
Hardness, Rockwell C |
36 |
36 |
|
Hardness, Vickers |
349 |
349 |
Thermal Properties
The thermal properties of grade 6 Ti-5Al-2.5Sn alloy are tabulated below.
|
Properties |
Metric |
Imperial |
|
Thermal expansion co-efficient (@0.000-100°C/32-212°F) |
9.40 µm/m°C |
5.22 µin/in°F |
|
Thermal conductivity |
7.80 W/mK |
54.1 BTU in/hr.ft².°F |
Other Designations
Equivalent materials to grade 6 Ti-5Al-2.5Sn alloy are as follows:
-
ASTM B265 Grade6
-
ASTM B348 Grade6
-
ASTM B381 Grade6
-
MIL-T-9046
-
MIL-T-9047
-
AMS 4926
-
AMS 4910
-
AMS 4966
-
AMS 4953
-
MIL F-83142
-
MIL T-81556
-
MIL T-81915
Fabrication and Heat Treatment
Machinability
Grade 6 Ti-5Al-2.5Sn 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 6 Ti-5Al-2.5Sn alloy can be hot or cold formed using power brake, hydropress, stretch or drop hammer methods.
Welding
Welding of grade 6 Ti-5Al-2.5Sn alloy is rated as good.
Annealing
Annealing of this material can be performed by heating to 718-843°C (1325-1550° F) for 4 h and then air cooled. In case intermediate stress relieving is required, the material has to be heated to 538-650 °C (1000-1200° F) for 1 h, and then air cooled.
Forging
Forging can be performed at 1010-1038°C (1850-1900°F) and completed at 954-1010°C (1750-1850°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 a moderately tempered austenitic stainless steel. Post-work annealing is recommended to re-attain favorable performance properties.
Applications
Grade 6 Ti-5Al-2.5Sn alloy is used in the following application areas:
-
Gas turbine engine casings and rings
-
Aerospace structural parts, aircraft engine and airframe.
-
Chemical processing equipment