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 divided into three types, namely, alpha-phase, beta-phase, and alpha-beta-phase. Alpha-phase titanium alloys are known to be stronger and less ductile. Beta-phase titanium alloys are more ductile. The third category of alpha-beta-phase titanium alloys strikes a balance between the other two categories with its mechanical properties.
Grade 6Al 6V 2Sn titanium alloy is an alpha-beta alloy that can be heat treated to higher strengths and heavier section sizes than titanium alloy 6AL-4V. This alloy possesses excellent strength, good corrosion resistance, and medium fabricability.
The following sections will discuss in detail about grade 6Al 6V 2Sn titanium alloy.
Chemical Composition
The chemical composition of grade 6Al 6V 2Sn titanium alloy is outlined in the following table.
|
Element |
Content (%) |
|
Titanium, Ti |
82.89 - 87.8 |
|
Aluminum, Al |
5-6 |
|
Vanadium, V |
5-6 |
|
Tin, Sn |
1.5 - 2.5 |
|
Iron, Fe |
0.35 - 1 |
|
Copper, Cu |
0.35 - 1 |
|
Oxygen, O |
≤ 0.20 |
|
Carbon, C |
≤ 0.050 |
|
Nitrogen, N |
≤ 0.040 |
|
Hydrogen, H |
≤ 0.015 |
|
Other, each |
≤ 0.10 |
|
Other, total |
≤ 0.30 |
Physical Properties
The physical properties of grade 6Al 6V 2Sn titanium alloy are tabulated below.
|
Properties |
Metric |
Imperial |
|
Density |
4.54 g/cm3 |
0.164 lb/in3 |
|
Melting point |
1627 - 1649°C |
2961 - 3000°F |
Mechanical Properties
The following table shows mechanical properties of grade 6Al 6V 2Sn titanium alloy.
|
Properties |
Metric |
Imperial |
|
Tensile strength |
1280 MPa |
186000 psi |
|
Yield strength |
1210 MPa |
175000 psi |
|
Poisson’s ratio |
0.32 |
0.32 |
|
Elastic modulus |
117 GPa |
117 GPa |
|
Shear modulus |
45 GPa |
6530 ksi |
|
Elongation at break |
10 % |
10 % |
|
Hardness, Brinell |
411 |
411 |
|
Hardness, Knoop |
450 |
450 |
|
Hardness, Rockwell C |
44 |
44 |
|
Hardness, Vickers |
430 |
430 |
Thermal Properties
The thermal properties of grade 6Al 6V 2Sn titanium 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 |
6.60 W/mK |
45.8 BTU in/hr.ft².°F |
Other Designations
Equivalent materials to grade 6Al 6V 2Sn titanium alloy are as follows:
|
AMS 4918 |
AMS 4936 |
AMS 4971 |
AMS 4978 |
|
DMS 1870 |
DMS 1887 |
MIL F-83142 |
MIL T-81556 |
|
MIL T-9047 |
AMS 4979 |
MIL T-9046 |
|
Fabrication and Heat Treatment
Machinability
Grade 6Al 6V 2Sn titanium alloy can be machined using slow speeds, right quantity of coolant flow 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 6V 2Sn titanium alloy can be hot or cold formed. Forming techniques include hydropress, stretch or drop-hammer.
Welding
Welding of grade 6Al 6V 2Sn titanium alloy should be performed at beta transus (F +/- 25) 1735.
Heat Treatment
The material can be solution treated at 843-913°C (1550-1675°F) for 1 h, and then water cooled.
Annealing
For annealing grade 6Al 6V 2Sn titanium alloy, the material has to be held at 704°C (1300°F) for 2 h, and air cooled. If stress relieving is required, the material has to be held at 593°C (1100°F) for 2 h and air cooled.
Forging
Rough forging can be performed at 932°C (1710°F), and completed at 843°C (1550°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 6V 2Sn titanium alloy can be performed at 538-621°C (1000-1150°F) for 4-8 h and air cooled.
Applications
Grade 6Al 6V 2Sn titanium alloy is chiefly used in plate and forging applications for rocket cases, airframe sections, and ordnance parts.