Titanium And Its Alloy

Ti and its alloys
Dra. A Salas Zamarripa October 2012

Why titanium?
!  The

primary reasons for which titanium alloys are used in aerospace applications include: !  Weight savings. The high strength-to-weight ratio of titanium alloys allows them to replace steel in many applications requiring high strength and fracture toughness. With a density of 016 lb/in3, titanium alloys are onlyabout ! as heavy as steel and nickel based superalloys, yielding excellent strength-to-weight ratios. !  Fatigue strength. Titanium alloys have much better fatigue strength than aluminum alloys and are frequently used for highly loaded bulkheads and frames in fighter aircraft.

Why titanium?
!  Operating

temperature capability. When the operating temperature exceeds about 270 F, aluminum alloyslose too much strength and titanium alloys are often required. !  Corrosion resistance. The corrosion resistance of titanium alloys is superior to both aluminum and steel alloys. !  Space savings. Titanium alloys are used for landing gear components on commercial aircraft where the size of aluminum components would not fit within the landing gear space envelope.

Ti and its alloys
!  Titaniumis named after the Titans, the powerful sons of the earth in Greek mythology. !  Titanium is the forth abundant metal on earth crust (~ 0.86%) after aluminium, iron and magnesium.

Ti and its alloys
!  Found

only in small amount in Thailand. !  Have similar strength as steel but with a weight nearly half of steel. !  Titanium is a lustrous, white metal when pure. !  The metal has a lowdensity, good strength, is easily fabricated, and has excellent corrosion resistance. !  The metal burns in air and is the only element that burns in The result from adding titanium nitrogen. powder to a burning mixture of potassium chlorate and sucrose !  It is marvelous in fireworks.

Ti and its alloys
!  Titanium

is resistant to dilute sulphuric and hydrochloric acid, most organic acids,damp chlorine gas, and chloride solutions. !  Titanium metal is considered to be physiologically inert. !  Titanium is present in meteorites and in the sun. !  Some lunar rocks contain high concentrations of the dioxide, TiO2. !  Pure titanium melts at 1670oC and has a density of 4.51 g cm-3.

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Pure Titanium
!  Pure

titanium melts at 1670oC and has a density of 4.51 g cm-3. !  Itshould therefore be ideal for use in components which operate at elevated temperatures, especially where large strength to weight ratios are required. !  Titanium can catch fire and cause severe damage in circumstances where it rubs against other metals at elevated temperatures. This is what limits its application in the harsh environment of aeroengines, to regions where the temperature does not exceed400oC.

Pure Titanium

8

Consequences of a titanium fire in an aeroengine. Nickel alloy blades have been burnt away. Photograph courtesy of Dr M. Hicks, RR.

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Pure Titanium
!  The

world production of titanium is nevertheless very small, hundreds of thousands of tons, which compares say with steel at 750 million tons per annum. !  80% of all the titanium produced is used in theaerospace industries. !  Car suspension springs could easily be made of titanium with a great reduction in weight but titanium is not available in the large quantities needed and certainly not at the price required for automobile applications. !  The target price for titanium needs to be reduced to about 30% of its current value for serious application in mass-market cars.

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Pure Titanium!  Pure

titanium has excellent resistance to corrosion and is used widely in the chemical industries. !  There is a passive oxide film which makes it particularly resistant to corrosion in oxidizing solutions. !  The corrosion resistance can be further improved by adding palladium (0.15 wt%). !  Most chemical plant use steel vessels which are clad with titanium. !  Titanium condenser tubes...