Titanium alloys

The material. The alloys of titanium have the highest strength-to-weight ratio of any structural metal, about 25% greater than the best alloys of alu­minum or steel. Titanium alloys can be used at temperatures up to 500°C; compressor blades of aircraft turbines are made of them. They have unu­sually poor thermal and electrical conductivity and low expansion coeffi­cients. The alloy Ti 6% Al 4% V is used in quantities that exceed those of all other titanium alloys combined. The data in this record describes it and similar alloys.

Composition

Ti + alloying elements, e. g., Al, Zr, Cr, Mo, Si, Sn, Ni, Fe, V.

General properties

Density

4400

– 4800

kg/m3

Price

96.9

– 107

USD/kg

Mechanical properties

Young’s modulus

110

– 120

GPa

Yield strength (elastic limit)

750

– 1200

MPa

Tensile strength

800

– 1450

MPa

Elongation

5

– 10

%

Hardness—Vickers

267

– 380

HV

Fatigue strength at 107 cycles

*589

– 617

MPa

Fracture toughness

55

– 70

MPa. m1/2

Thermal properties

Melting point

1480

– 1680

°C

Maximum service temperature Thermal conductor or insulator?

450 – 500 Poor conductor

°C

Thermal conductivity

7

– 14

W/m. K

Specific heat capacity

645

– 655

J/kg. K

Thermal expansion coefficient

8.9

– 9.6

p, strain/°C

Electrical properties

Electrical conductor or insulator?

Good conductor

Electrical resistivity

100

– 170

puhm. cm

Adiabatic heating heats the air in the compressor to about 500°C, requiring the use of titanium alloys for the blades. (Reproduced with the permission of Rolls-Royce plc, © Rolls-Royce plc 2004.)

Ecoproperties: material

Annual world production

120 X 105

– 122 X 103

tonne/yr

Reserves

50 X 106

– 52 X 106

tonne

Embodied energy, primary production

600

– 740

MJ/kg

CO2 footprint, primary production

*38

– 44

kg/kg

Water usage

*470

– 1410

l/kg

Ecoproperties: processing

Casting energy

5.02

– 5.77

MJ/kg

Casting CO2

0.301

– 0.346

kg/kg

Forging, rolling energy

*4.71

– 5.7

MJ/kg

Forging, rolling CO2

*0.377

– 0.456

kg/kg

Recycling

Embodied energy, recycling

228

– 281

MJ/kg

CO2 footprint, recycling

*14.4

– 16.7

kg/kg

Recycle fraction in current supply

20

– 24

%

Typical uses. Aircraft turbine blades; general aerospace applications; chemi­cal engineering; pressure vessels; high-performance automotive parts such as connecting rods; heat exchangers; bioengineering; medical; missile fuel tanks; compressors; valve bodies; light springs, surgical implants; marine hardware, paper-pulp equipment; sports equipment such as golf clubs and bicycles.