Zirconium alloys: composition, properties, application

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

The use of zirconium alloy is currently quite widespread in medicine and nuclear energy. In other industries, this material is also used, but to a lesser extent. It is worth noting that various alloys from this raw material have gained popularity. By itself, zirconium has not become a popular material, since its quality is much worse than that of an alloy of the same metal.

General information

Zirconium (Zr) is an element of the periodic table whose atomic number is 40 and its atomic weight is 91.22. Under normal condition and under normal conditions, this material is a lustrous metal with a silvery white tint. The density of such raw materials reaches 6.45 g/cm3. This metal in its pure form, which does not contain any impurities, is distinguished by the fact that it has a very high ductility, and it is very easy to process both cold and hot. It is worth noting here that this raw material, like titanium, for example, will sharply lose its mechanical properties if it is combined with impurities of non-metallic substances. Zirconium and oxygen are considered the worst compounds.

Material properties andalloy

Zirconium itself is distinguished by the fact that it has a fairly high resistance to various acids. This raw material does not dissolve in an environment such as nitric and hydrochloric acid or alkali. This feature is key. On its basis, many zirconium alloys are created. For example, if you take multicomponent magnesium alloys and add an element such as zirconium to them, the material will become much more resistant to corrosion. If you create an alloy of titanium and zirconium, then the acid resistance of the first element will increase.

It is also worth noting that all zirconium alloys with other metals are characterized by the fact that they do not lose their toughness in a wide temperature range, the resistance to mechanical shock remains at a very high level. An example is a magnesium alloy with a few percent zinc and only a few tenths of a percent zirconium. The resulting metal will be almost twice as strong as magnesium, and it will also be able to maintain its strength at temperatures up to 200 degrees Celsius.

Description of features

Zirconium alloys are most actively used in such areas as fuel element cladding, fuel channel pipes, and various parts of fuel assemblies. Zirconium itself is also characterized by the fact that the neutron absorption cross section is quite low. According to this indicator, it is second only to such substances as magnesium and beryllium. In addition, the melting point of zirconium is very high.

Zirconium alloys used in various industries are characterized by the fact that they have very high corrosion resistance in water, in steam-water mixture, in saturated and superheated steam up to a temperature of about 350-360 degrees Celsius. It is also worth noting that this temperature limit is expected to be raised to higher values in the near future.

Alloy parameters

Properties of zirconium alloys in terms of mechanical stability are quite high, which cannot be said about pure zirconium. It is by alloying that the high strength of the material is achieved. For example, an alloy such as niobium (Nb) and 1% zirconium (Zr) will be characterized by the fact that the yield strength of the material at temperatures of 20, 200, 300 and 400 degrees Celsius will be 200, 160, 120 and 90 MPa. This alloy is actively used for fuel rod cladding. And, for example, if you change the composition of the zirconium alloy with niobium, that is, increase the zirconium content to 2.5%, then the yield strength will increase to 280, 220, 200 and 180 MPa, at the same temperatures.

However, such materials have their drawbacks. The disadvantages include the fact that the alloy with zirconium turns out to be too creepy when the temperature reaches 320-350 degrees Celsius and above. Another disadvantage is that Zr actively dissolves hydrogen, which often occurs during corrosion. Because of this, substances such as zirconium hydrides will be formed, which greatly reduce the ductility of the raw material, which makes the metal more brittle.

Zirconium in medicine

Zirconium alloys are used quite actively in medicine. Scientists through experiments have found that even wearing simple zirconium bracelets can help treat certain diseases, and it can also increase a person's overall well-being.

Today, implants (retainers) are often used in such areas of medicine as traumatology and maxillofacial surgery. Fixators are used for fractures, fixing the bones so that they do not move. It is in these cases that one can distinguish such advantages of using zirconium alloys as: high biological compatibility (meaning the absence of allergic reactions of the human body to such an alloy or rejection), high strength characteristics of the alloy, which is very important for fixators. It is also worth noting that the absence of rejection or allergy to such a substance led to the fact that there was no need to repeat the surgical operation to remove the retainer if the body suddenly began to reject the implant.

Zirconium in nuclear power industry

Until the 50s of the last century, it was believed that zirconium was not suitable for use in this area. However, it was in the 50s. For the first time, a material was obtained that was completely purified from such an impurity as hafnium. After purification, it turned out that pure zirconium has a very small thermal neutron absorption cross section. It was this quality that became the main one and made it possible to use zirconium alloys in the nuclear power industry.

It should be added that simply purified zirconium could not be used because the corrosion resistance was too low in hot water. After that, it was decided to use zirconium-based alloys. They have proven their worth in steam-cooled reactors and similar corrosive environments.

General applications of alloys

Zirconium is widely used as an alloying element. This is due to the fact that the metals to which this substance is added become more heat-resistant, acid-resistant, etc. That is, the alloy of metal and zirconium greatly exceeds the initial raw material in its characteristics.

Ferrozirconium is quite widely used. It is an alloy of zirconium and iron. The content of the alloying element Zr reaches 20% of the total mass. Such a substance is used in metallurgy as a deoxidizer and degasser for steel. Aluminum-zirconium alloys, for example, are considered the most resistant to corrosion and are used in cathode grids for vacuum tubes. The content of Zr in such an alloy is not more than 3% of the total mass.

In ferrous metallurgy, in addition to ferrozirconium, an alloy of Zr and silicon is often used. It is used for degassing steel. An alloy of copper and zirconium is widely used for the manufacture of conductive elements for electrical equipment.

Finding zirconium

It is worth noting that zirconium is a rather rare element. The content of this substance in the earth's crust does not exceed0.025% by weight. Zirconium occupies the twelfth line in the table of prevalence of metals. This raw material is quite dispersed, and therefore it is very difficult to find any large deposits of it. It is most commonly found as a chemical compound located in the lithosphere, as zirconium itself is a lithophile element.