Grade 6 Ti-5Al-2.5Sn Alloy (UNS R54520)

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

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