The use of zirconium alloy is currently quite widespread in medicine and nuclear energy. In other industries, this material is also used, but with a smaller share. It is worth noting that it was various alloys from these raw materials that gained popularity. Zirconium itself did not become a popular material, since its quality is much worse than directly from an alloy of the same metal.
General information
Zirconium (Zr) is an element of the periodic table, the atomic number of which is 40, and its atomic weight is 91.22. Under normal conditions and under normal conditions, this material is a shiny metal with a silver-white tint. The density of such raw materials reaches 6.45 g / cm 3 . This metal in its pure form, which does not contain any impurities, is characterized in that it has a very high ductility and 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 combined with impurities of non-metallic substances. The worst compounds are zirconium and oxygen.
Material and alloy properties
Zirconium itself is distinguished by the fact that it has a fairly high resistance to various acids. This raw material does not dissolve in such an environment as nitric and hydrochloric acid or alkalis. 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 viscosity in a wide temperature range, the resistance to mechanical shock is kept at a very high level. You can give an example of a magnesium alloy with several percent of zinc and with only a few tenths of a percent of zirconium. The resulting metal will be almost twice as strong as simple magnesium, and it will also be able to maintain its strength at temperatures up to 200 degrees Celsius.
Description of characteristics
Zirconium alloys are most actively used in areas such as cladding of fuel elements, pipes of fuel channels, various parts of fuel assemblies. Zirconium itself is also characterized by the fact that the neutron absorption cross section is quite low. In terms of this indicator, it is second only to substances such 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 a steam-water mixture, in saturated and superheated steam up to a temperature of about 350-360 degrees Celsius. It is also worth noting that in the near future it is expected that this temperature limit will be raised to higher values.
Alloy parameters
The properties of zirconium alloys in terms of mechanical stability are quite high, which cannot be said about pure zirconium. It is by alloying that a high material strength 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. Such an alloy is actively used for cladding of fuel elements. 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. By cons, the alloy with zirconium turns out to be too creeping when the temperature reaches 320-350 degrees Celsius and above. Another drawback 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 fragile.
Zirconium in medicine
Zirconium alloys in medicine are used quite actively. Scientists through experiments have found that even wearing simple zirconia bracelets can help in the treatment of certain diseases, and it can also increase the overall well-being of a person.
Today, implants (fixatives) 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 such advantages of using zirconium alloys can be distinguished 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 fixatives. It is also worth noting that the absence of rejection or allergy to such a substance has led to the fact that there is no longer a need for repeated surgery to remove the fixative, if suddenly the body began to reject the implant.
Zirconium in nuclear energy
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. a material was obtained for the first time that was completely free of impurities such as hafnium. After purification, it turned out that pure zirconium has a very small absorption cross section for thermal neutrons. It was this quality that became the main one and made it possible to use zirconium alloys in nuclear energy.
It is worth adding that it was not possible to use simply purified zirconium because the corrosion resistance was too low in hot water. After that, it was decided to use precisely zirconium-based alloys. They have proven themselves in applications in reactors with a steam-water coolant, as well as in other similar aggressive environments.
General use of alloys
Zirconium is very 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 materials in their characteristics.
Ferrozirconium is quite widely used. This is an alloy of zirconium with 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 a 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. Apply it to steel degassing. The 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 poorly distributed element. The content of this substance in the earth's crust does not exceed 0.025% by weight. In the prevalence table of metals, zirconium occupies the twelfth line. This raw material is rather dispersed, and therefore it is very difficult to find it at least some large deposits. Most often, it is found as a chemical compound located in the lithosphere, since zirconium itself is a lithophilic element.