Grade 5 Ti-6Al-4V Alloy (UNS R56200)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
     Machinability
     Forming
     Welding
     Annealing
     Heat Treatment
     Forging
     Hot Working
     Cold Working
     Aging
Applications

Introduction

Titanium alloys are known to be light weight alloys with excellent corrosion resistance, very high tensile strength and toughness.

Grade 5 Ti-6Al-4V alloy is the most widely used of all the titanium grades. It is a medium to high strength general-purpose alloy. It is also referred to as an alpha-beta alloy. This alloy is fully heat treatable in sections measuring up to 15mm. It can be heated up to 400°C (750°F), and has good tensile properties at room temperature, creep resistance up to 325°C and very good fatigue strength. It is also known to be highly resistant to general corrosion in sea water.

The following sections will discuss in detail about grade 5 Ti-6Al-4V alloy.

Chemical Composition

The chemical composition of grade 5 Ti-6Al-4V alloy is outlined in the following table.

Element Content (%)
Titanium, Ti 87.6 - 91
Aluminum, Al 5.5 - 6.75
Vanadium, V 3.5 - 4.5
Iron, Fe ≤ 0.40
Oxygen, O ≤ 0.20
Carbon, C ≤ 0.080
Nitrogen, N ≤ 0.050
Hydrogen, H ≤ 0.015

Physical Properties

The physical properties of grade 5 Ti-6Al-4V alloy are tabulated below.

Properties Metric Imperial
Density 4.43 g/cm3 0.160 lb/in3
Melting point 1674 °C 3045 °F

Mechanical Properties

The following table shows mechanical properties of grade 5 Ti-6Al-4V alloy.

Properties Metric Imperial
Tensile strength ≥ 895 MPa ≥ 130000 psi
Yield strength ≥ 828 MPa ≥ 120000 psi
Poisson’s ratio 0.31 0.31
Elastic modulus 105-120 GPa 15200-17400 ksi
Shear modulus 41-45 GPa 5950-6530 ksi
Elongation at break ≥ 10 % ≥ 10 %

Thermal Properties

The thermal properties of grade 5 Ti-6Al-4V 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 6.60W/mK 45.8 BTU in/hr.ft².°F

Other Designations

Equivalent materials to grade 5 Ti-6Al-4V alloy are as follows:

AMS 4928 AMS 4965 AMS 4967 MIL T-81915 MIL T-9046
AMS 4920 AMS 4954 ASTM B265 MIL T-81556 MIL T-9047
AMS 4911 AMS 4935 ASTM B348 MIL F-83142 SPS M618
AMS 4906 AMS 4934 ASTM B381 GE C50TF12 DMS 1570
AMS 4905 AMS 4930 DIN 3.7164    

Fabrication and Heat Treatment

Machinability

Although tough, grade 5 Ti-6Al-4V 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 5 Ti-6Al-4V alloy can be hot or cold formed. The forming techniques include hydropress, stretch or drop-hammer.

Welding

Weldability of grade 5 Ti-6Al-4V alloy is rated as fair.

Annealing

Annealing can be performed by holding at 732°C (1350°F) between 1/4 and 4 h, then furnace cooled to 566°C (1050°F) followed by air cooling. In case of forgings and bars, furnace cooling is not required.

Heat Treatment

Solution treatment of the material is done at 904-954°C (1660-1750° F) for 2 h, which is followed by water quench process.

Forging

Rough forging of grade 5 Ti-6Al-4V alloy should be performed at 982°C(1800°F), and finished at 968°C (1750°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.

Aging

Aging of grade 5 Ti-6Al-4V alloy can be performed at 538°C (1000°F) for 4 h, and then air cooled.

Applications

Grade 5 Ti-6Al-4V alloy is a popular titanium alloy and is widely used in several industries including aerospace, power generation, marine, and offshore industries.

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