Grade Ti 6Al 2Nb 1Ta 1Mo Alloy

Topics Covered

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

Introduction

Titanium alloys possess very good corrosion resistance, high tensile strength and toughness. They are also light weight. Grade Ti 6Al 2Nb 1Ta 1Mo alloy is a near alpha wrought alloy.

Near-alpha alloys contain small amount of ductile beta-phase. Along with alpha-phase stabilizers, near-alpha alloys are alloyed with 1-2% of beta phase stabilizers such as silicon, molybdenum, or vanadium.

Grade Ti 6Al 2Nb 1Ta 1Mo alloy is known to possess high toughness, medium strength, weldability, and resistance to seawater corrosion. It is however not heat-treatable.

The following sections will discuss in detail about grade Ti 6Al 2Nb 1Ta 1Mo alloy.

Chemical Composition

The chemical composition of grade Ti 6Al 2Nb 1Ta 1Mo alloy is outlined in the following table.

Element Content (%)
Aluminum, Al 5.5 - 6.5
Niobium, Nb 1.5 - 2.5
Tantalum, Ta 0.5 - 1.5
Molybdenum, Mo 0.5 - 1
Iron, Fe 0.25 max
Oxygen, O 0.1 max
Carbon, C 0.05 max
Nitrogen, N 0.03 max
Hydrogen, H 0.0125 max
Titanium, Ti Remainder

Physical Properties

The physical properties of grade Ti 6Al 2Nb 1Ta 1Mo alloy are tabulated below.

Properties Metric Imperial
Density 4.48 g/cm3 0.162 lb/in3
Melting point ≤ 1650 °C ≤ 3000 °F

Mechanical Properties

The following table shows mechanical properties of grade Ti 6Al 2Nb 1Ta 1Mo alloy.

Properties Metric Imperial
Tensile strength 830 MPa 120000 psi
Yield strength 730 MPa 106000 psi
Poisson’s ratio 0.31 0.31
Elastic modulus 113.8 GPa 16510 ksi
Shear modulus 43.4 GPa 6290 ksi
Elongation at break 13% 13%
Hardness, Brinell 290 290
Hardness, Knoop 315 315
Hardness, Rockwell C 30 30
Hardness, Vickers 304 304

Thermal Properties

The thermal properties of grade Ti 6Al 2Nb 1Ta 1Mo 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 6.40 W/mK 44.4 BTU in/hr.ft².°F

Other Designations

Equivalent material to grade Ti 6Al 2Nb 1Ta 1Mo alloy is MIL-T-9046.

Fabrication and Heat Treatment

Machinability

Grade Ti 6Al 2Nb 1Ta 1Mo 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 Ti 6Al 2Nb 1Ta 1Mo alloy can be hot or cold formed.

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 Ti 6Al 2Nb 1Ta 1Mo alloy is chiefly used in marine and sub-marine vehicles for their hardware and hull structures and in naval aircraft.

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