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Titanium Alloys - Ti3Al2.5V Grade 9 and Grade 18

Chemical Formula

Ti3Al2.5V

Background

Ti3Al2.5V (Grade 9)

This alloy is sometimes referred to as ‘half 6-4’. It offers 20 to 50% higher strength than commercially pure grades, but is more formable and weldable than Ti6Al4V. It is principally used as tubing in aircraft engine hydraulic systems, for high strength corrosion resisting applications such as golf club shafts, tennis rackets, bicycle frames etc.

Ti3Al2.5V0.05Pd (Grade 18)

Grade 18 is identical to Grade 9 with the exception of the addition of palladium to increase the corrosion resistance. Mechanical and physical properties, specifications and forms are all identical to those of Grade 9.

The alloys composition differs by the addition of 0.04-0.08% Pd.

Composition

Table 1. The composition of Ti3Al2.5.

Content

C

<0.08%

N2

<0.03%

O2

<0.15%

V

2.0-3.0%

Al

2.5-3.5%

Fe

<0.25%

H2

<0.015%

Ti

Balance

Designations

Other designations for Ti3Al2.5 include:

        AMS 4943

        AMS 4944

        AMS 4945

        ASTM B265 Gr9 and Gr18

        ASTM B337 Gr9

        ASTM B338 Gr9 and Gr18

        ASTM B348 Gr9 and Gr18

        ASTM B381 Gr9

        MIL –T –9047

        MIL –T –9046 AB5

        ASTM B264 Gr9

        ASTM B348 Gr9

        UNS R56320   Grade 9

        UNS 56322   Grade 18

Key Properties

Physical Properties

Table 2. Typical physical properties for Ti3Al2.5.

Property

Typical Value

Density g/cm3 (lb/ cu in)

4.48 (0.161)

Melting Range °C±15°C (°F)

1704 (3099)

Volume Electrical Resistivity ohm.cm (phm.in)

124 (49)

Thermal Conductivity W/m.K (BTU/ft.h.°F)

7.6 (53)

Mean Co-Efficient of Thermal Expansion 0-300°C /°C (0-572°F /°F)

7.9x10-6 (4.4)

Beta Transus °C±15°C (°F)

935 (1715)

Mechanical Properties

Table 3. Typical mechanical properties for Ti3Al2.5 (data obtained for bar and plate 1” (25.4mm) thick, annealed.

Property

Minimum

Typical Value

Tensile Strength MPa (ksi)

621 (90)

740 (107)

0.2% Proof Stress MPa (ksi)

483 (70)

607 (88)

Elongation Over 2 Inches %

15

17

Elastic Modulus GPa (msi)

91 (13)

Hardness Rockwell C

15

Specified Bend Radius <0.070 in x Thickness

2.5

Charpy, V-notch Impact J (ft.lbf) (L-Direction pipe)

48 (35)

Short-term Creep 1% strain MPa (ksi) (1000 hrs @ 250°C (480°F))

400 (58)

Stress Rupture MPa (ksi) (1000 hrs @ 250°C (480°F))

421 (61)

Fabrication

        Weldability – Good

        Forging – Rough 871-899°C (1600-1650°F), finish 843-871°C (1550-1600°F)

        Annealing – 593-760°C (1100-1400°F), 1-3hr, AC

        Solution Treating – 871-927°C (1600-1700°F), 15-20 min, WQ.

        Ageing – 482-510°C (900-950°F), 2-8hr, AC.

        Stress Relief Annealing – 316-649°C (600-1200°F), 1-3 hrs, AC.

Applications

As mentioned previously, this alloy is primarily used in golf club shafts, tennis rackets and bicycle frames.

Source: Titanium Information Group.

For more information on this source please visit Titanium Information Group.

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