Grade 6Al 2Sn 4Zr 2Mo Titanium Alloy (UNS R54620)

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.

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