Jul 5 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
Commercially pure titanium alloys are available in many forms. The content of oxygen and iron influences their mechanical properties. Each commercial grade is designed to meet the needs for different applications.
Grade 4 Unalloyed Ti ("Pure") 75A alloy is the highest strength of all the unalloyed grades. It is known to possess good ductility and medium formability. Good strength to weight ratio is well maintained at moderate temperatures. At low temperatures, this alloy also has good impact properties.
The following sections will discuss in detail about grade 4 Unalloyed Ti ("Pure") 75A alloy.
Chemical Composition
The chemical composition of grade 4 Unalloyed Ti ("Pure") 75A alloy is outlined in the following table.
|
Element |
Content (%) |
|
Titanium, Ti |
≥ 98.6 |
|
Iron, Fe |
≤ 0.50 |
|
Oxygen, O |
≤ 0.40 |
|
Carbon, C |
≤ 0.080 |
|
Nitrogen, N |
≤ 0.050 |
|
Hydrogen, H |
≤ 0.015 |
Physical Properties
The physical properties of grade 4 Unalloyed Ti ("Pure") 75A alloy are tabulated below.
|
Properties |
Metric |
Imperial |
|
Density |
4.51 g/cm3 |
0.163 lb/in3 |
|
Melting point |
1660°C |
3020°F |
Mechanical Properties
The following table shows mechanical properties of grade 4 Unalloyed Ti ("Pure") 75A alloy.
|
Properties |
Metric |
Imperial |
|
Tensile strength |
680 MPa |
98600 psi |
|
Yield strength |
560 MPa |
81200 psi |
|
Poisson's ratio |
0.34-0.40 |
0.34-0.40 |
|
Elastic modulus |
105 - 120 GPa |
15200 - 17400 ksi |
|
Elongation at break |
23% |
23% |
|
Hardness (HV) |
250 |
250 |
Thermal Properties
The thermal properties of grade 4 Unalloyed Ti ("Pure") 75A are tabulated below.
|
Properties |
Metric |
Imperial |
|
Thermal expansion co-efficient (@0.000-100°C/32-212°F) |
8.60 µm/m°C |
4.78 µin/in°F |
|
Thermal conductivity |
16.95 W/mK |
117.6 BTU in/hr.ft².°F |
Other Designations
Equivalent materials to grade 4 Unalloyed Ti ("Pure") 75A alloy are as follows:
|
ASTM B348 |
ASTM F67 |
MIL T-9046 |
MIL T-9047 |
|
ASTM B265 |
ASTM F468 (4) |
MIL T-81556 |
ASTM B381 |
|
AMS 4921 |
ASTM F467 (Ti-4) |
MIL F-83142 |
ASTM F67 (4) |
AMS 4901
|
|
|
|
Fabrication and Heat Treatment
Machinability
Grade 4 Unalloyed Ti ("Pure") 75A 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 4 Unalloyed Ti ("Pure") 75A alloy can be hot or cold formed using power brake, hydropress, stretch or drop hammer methods.
Welding
Weldability of grade 4 Unalloyed Ti ("Pure") 75A alloy is rated as good.
Annealing
Annealing of this material can be performed by heating to 704°C (1299°F), and then held for 2 h, which should be followed by air cooling. In case intermediate stress relieving is required, the material has to be heated to 482-538°C (900-100-°F) for 45 min.
Forging
Rough forging can be performed at 935°C (1715°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 a moderately tempered austenitic stainless steel. Post-work annealing is recommended to re- attain favorable performance properties.
Applications
Grade 4 Unalloyed Ti ("Pure") 75A alloy is used in the following: