Top Ten Properties of Titanium

(1) low density, high strength, specific strength

Titanium density is 4.51g/cm3, 57% of steel, titanium is less than two times heavier than aluminum, three times stronger than aluminum. Titanium alloy specific strength (strength / density ratio) is commonly used in industrial alloys in the large (see Table 2-1), titanium alloy specific strength is 3.5 times stainless steel; aluminum alloy 1.3 times; magnesium alloy 1.7 times, so it is the aerospace industry is essential to the structure of the material.
(2) Excellent corrosion resistance

The passivity of titanium depends on the presence of oxide film, and its corrosion resistance in oxidizing medium is much better than in reducing medium. High rate corrosion occurs in reducing media. Titanium does not corrode in some corrosive media, such as seawater, wet chlorine gas, chlorite and hypochlorite solutions, nitric acid, chromic acid, metal chlorides, sulfides, and organic acids. However, in media that react with titanium to produce hydrogen (e.g. hydrochloric and sulfuric acids), titanium usually has a large corrosion rate. However, if a small amount of oxidizing agent is added to the acid, a passivation film will form on the surface of titanium. Therefore, titanium is corrosion-resistant in strong sulfuric acid-nitric acid or hydrochloric acid-nitric acid mixtures, and even in hydrochloric acid containing free chlorine. The protective oxide film of titanium is often formed when the metal encounters water, even in small amounts of water or water vapor. If titanium is exposed to a strongly oxidizing environment in the complete absence of water, rapid oxidation occurs and violent reactions and even spontaneous combustion often occur. Such phenomena have occurred when titanium reacts with fuming nitric acid containing excess nitrogen oxide, and when titanium reacts with dry chlorine gas. Therefore, a certain amount of water is necessary to prevent such reactions.

(3) Good heat resistance

Usually aluminum at 150 ℃, stainless steel at 310 ℃ that is the loss of the original performance, and titanium alloys at 500 ℃ or so still maintain good mechanical properties. When the aircraft speed reaches 2.7 times the speed of sound, the surface temperature of the aircraft structure reaches 230 ℃, aluminum alloys and magnesium alloys can not be used, while titanium alloys can meet the requirements. Titanium's heat resistance is good, it is used for aero-engine compressor disk and blade and the skin of the rear fuselage of the aircraft.
(4) Good low-temperature performance

Certain titanium alloys (such as Ti - 5AI - 2.5SnELI) strength with the reduction of temperature and increase, but the plasticity of the reduction is not much, at low temperatures still have good ductility and toughness, suitable for use in ultra-low temperatures. Can be used in dry liquid hydrogen and liquid oxygen rocket engines, or in manned spacecraft for ultra-low temperature containers and storage boxes.

(5) non-magnetic

Titanium is non-magnetic, it is used in submarine shells, will not cause the explosion of mines.

(6) Small thermal conductivity
Titanium's thermal conductivity is small, only 1/5 of steel, aluminum 1/13, copper 1/25. poor thermal conductivity is a disadvantage of titanium, but in some cases you can use this feature of titanium.
(7) Low modulus of elasticity
The modulus of elasticity of titanium is only 55% of that of steel, so when used as a structural material, low modulus of elasticity is a disadvantage.

(8) Tensile strength and yield strength are close to each other.

Ti-6AI-4V titanium alloy tensile strength of 960MPa, yield strength of 892MPa, the difference between the two is only 58MPa.
(9) Titanium is easily oxidized at high temperature.

Titanium and hydrogen-oxygen bonding force is strong, we must pay attention to prevent oxidation and hydrogen absorption. Titanium welding should be carried out under argon protection to prevent contamination. Titanium tube and sheet should be heat-treated under vacuum, titanium forgings heat treatment to control the micro-oxidizing atmosphere.

(10) low damping resistance

Titanium and other metal materials (copper, steel) made of the same shape and size of the clock, with the same force to each clock will find that the clock made of titanium oscillates up to the sound of a long time, that is, by striking the energy given to the clock is not easy to disappear, so we say that titanium's damping performance is low.