Ten properties of titanium
Low density and high specific strength
The density of titanium is 4.51g/cm3,which is higher than that of aluminum and lower than that of steel,copper and nickel,but the specific strength is the first of metals.
Titanium is a very active metal,its equilibrium potential is very low,and its thermodynamic corrosion tendency in medium is large.But in fact,titanium is very stable in many media.For example,titanium is corrosion-resistant in oxidizing,neutral and weak reducing media.This is because titanium has a great affinity with oxygen.In air or oxygen-containing medium,a dense,strong adhesion and inert oxide film is formed on the surface of titanium to protect the titanium matrix from corrosion.Even due to mechanical wear,it will heal or regenerate quickly.This indicates that titanium is a metal with strong passivation tendency.When the medium temperature is below 315℃,the oxide film of titanium always maintains this characteristic.
In order to improve the corrosion resistance of titanium,surface treatment technologies such as oxidation,electroplating,plasma spraying,ion nitriding,ion implantation and laser treatment were studied,which enhanced the protection of titanium oxide film and obtained the desired corrosion resistance effect.According to the needs of metal materials in the production of sulfuric acid,hydrochloric acid,methylamine solution,high-temperature wet chlorine and high-temperature chloride,a series of corrosion-resistant titanium alloys such as titanium molybdenum,titanium palladium and titanium molybdenum nickel have been developed.Titanium-32 molybdenum alloy is used in titanium castings,titanium-0.3 molybdenum-0.8 nickel alloy is used in the environment where crevice corrosion or pitting corrosion often occurs,or titanium-0.2 palladium alloy is used locally in titanium equipment,which has achieved good application results.
Good heat resistance
The new titanium alloy can be used for a long time at 600℃or higher.
Good low temperature resistance
Titanium alloys TA7(ti-5al-2.5sn),TC4(Ti-6Al-4V)and ti-2.5zr-1.5mo are representative of low-temperature titanium alloys.Their strength increases with the decrease of temperature,but their plasticity changes little.It maintains good ductility and toughness at the low temperature of-196-253℃and avoids the cold brittleness of metal.It is an ideal material for low-temperature containers,storage tanks and other equipment.
Strong damping resistance
Compared with steel and copper,titanium has the longest vibration attenuation time after mechanical and electrical vibration.This property of titanium can be used as tuning fork,vibration element of ultrasonic crusher in medicine and vibration film of advanced sound speaker.
Non magnetic and non-toxic
Titanium is a non-magnetic metal,which will not be magnetized in a large magnetic field.It is non-toxic and has good compatibility with human tissue and blood,so it is adopted by the medical community.
The tensile strength is close to its yield strength
This property of titanium shows that its yield strength ratio(tensile strength/yield strength)is high,which indicates that the plastic deformation of titanium material is poor during forming.Due to the large ratio of yield limit to elastic modulus of titanium,the resilience of titanium during forming is large.
Good heat exchange performance
Although the thermal conductivity of titanium is lower than that of carbon steel and copper,the wall thickness can be greatly reduced due to the excellent corrosion resistance of titanium.Moreover,the heat exchange mode between the surface and steam is drop condensation,which reduces the heat group.Without scaling on the surface,it can also reduce the thermal resistance and significantly improve the heat exchange performance of titanium.
Low elastic modulus
The elastic modulus of titanium is 106.4gmpa at room temperature,which is 57%of that of steel.
Titanium is a very active metal with chemical properties.It can react with many elements and compounds at high temperature.Titanium gettering mainly refers to the reaction with carbon,hydrogen,nitrogen and oxygen at high temperature.