Titanium is a highly reactive metal with a very low equilibrium potential and a strong thermodynamic corrosion tendency in media

Abstract:

Low density and high specific strength

The density of metallic titanium is 4.51g/cm ³, which is higher than that of aluminium but lower than that of steel, copper and nickel. However, its specific strength ranks first among metals.

Corrosion resistance performance

Titanium is a highly reactive metal with a very low equilibrium potential and a strong thermodynamic corrosion tendency in media. But in fact, titanium is very stable in many media. For instance, titanium is corrosion-resistant in oxidizing, neutral and weakly reducing media. This is because titanium has a strong affinity for oxygen. In the air or in oxygen-containing media, a dense, highly adhesive and inert oxide film forms on the surface of titanium, protecting the titanium substrate from corrosion. Even if it is due to mechanical wear and tear, it will quickly heal itself or regenerate. This indicates that titanium is a metal with a strong tendency to passivate. The oxide film of titanium always maintains this property when the medium temperature is below 315℃.

To enhance the corrosion resistance of titanium, surface treatment technologies such as oxidation, electroplating, plasma spraying, ion nitriding, ion implantation and laser treatment have been developed, which have strengthened the protective effect on the oxide film of titanium and achieved the desired corrosion resistance. In response to the demand for metallic materials in the production of sulfuric acid, hydrochloric acid, methylamine solution, high-temperature wet chlorine gas and high-temperature chlorides, a series of corrosion-resistant titanium alloys such as titanium-molybdenum, titanium-palladium and titanium-molybdenum-nickel have been developed. Titanium castings are made of titanium-32 molybdenum alloy. For environments where crevice corrosion or pitting corrosion often occurs, titanium-0.3 molybdenum-0.8 nickel alloy is used, or titanium-0.2 palladium alloy is used locally in titanium equipment. All of these have achieved excellent application results.

Good heat resistance

The new type of titanium alloy can be used for a long time at temperatures of 600℃ or higher.

It has good low-temperature resistance

Low-temperature titanium alloys represented by titanium alloys such as TA7 (Ti-5Al-2.5Sn),TC4(Ti-6Al-4V), and Ti-2.5Zr-1.5Mo have their strength increase with the decrease of temperature, but the plasticity change is not significant. It maintains good ductility and toughness at low temperatures ranging from -196 to 253℃, avoiding the cold brittleness of metals. It is an ideal material for low-temperature containers, storage tanks and other equipment.

It has strong anti-damping performance

Compared with steel and copper metals, titanium has the longest self-vibration attenuation time after being subjected to mechanical and electrical vibrations. This property of titanium can be utilized to make tuning forks, vibration components of ultrasonic disintegrators in medicine, and vibration films for high-end audio speakers, etc.

Non-magnetic and non-toxic

Titanium is a non-magnetic metal that will not be magnetized even in a very strong magnetic field. It is non-toxic and has good compatibility with human tissues and blood, which is why it is adopted by the medical field.

The tensile strength is close to its yield strength

This property of titanium indicates that its yield-to-tensile ratio (tensile strength/yield strength) is high, suggesting that the plastic deformation of metallic titanium materials is poor during forming. Due to the large ratio of titanium's yield limit to its elastic modulus, titanium has a strong resilience during molding.

Good heat exchange performance

Although the thermal conductivity of titanium is lower than that of carbon steel and copper, due to titanium's excellent corrosion resistance, the wall thickness can be significantly reduced. Moreover, the heat exchange mode between the surface and steam is droplet condensation, which reduces the heat group. The absence of scale formation on the surface can also reduce thermal resistance, thereby significantly improving the heat exchange performance of titanium.

Low elastic modulus

The elastic modulus of titanium at room temperature is 106.4GMPa, which is 57% of that of steel.

Suction performance

Titanium is a metal with highly reactive chemical properties and can react with many elements and compounds at high temperatures. Titanium gas absorption mainly refers to the reactions with carbon, hydrogen, nitrogen and oxygen at high temperatures.