Solid solutions are phases in which one of the components (the solvent) retains its crystal lattice, and the atoms of the other (soluble) components are located in its lattice, distorting it.
Throughout the history of the metallurgical industry, the study of solid solutions has been one of the key aspects of understanding and improving the properties of metal alloys. Solid solutions are the basis for creating a variety of materials, ranging from bronze, brass, stainless and structural steels, to high-strength alloys, including magnesium and aluminum. These materials play a key role in creating strong and lightweight structures, being used in various fields, including aviation and the automotive industry.
The properties of solid solutions are actively regulated by their composition and production technology, especially by thermal or thermomechanical treatment processes. This allows engineers and metallurgists to create materials with specific mechanical and chemical properties.
When moving from one solid solution to another, steels and alloys can acquire new, sometimes unique, properties. For example, how does this happen when hardening steels. At the beginning of the material heating process, the crystal lattice expands, and the atoms of the alloy elements dissolve in the basic metal matrix, forming a solid solution. When steel is cooled, the crystal lattice is compressed. The result is martensite, which has a different crystal structure than the original austenite. This change in the crystal lattice of the material affects its mechanical properties, in particular, increases its hardness and strength.
Dispersive hardening (aging) is also accompanied by changes in the crystalline structure of the material: the supersaturated solid solution decomposes and new phases are released that strengthen the material. This process is typical, for example, for alloys aluminum.
The materials distinguish three main types of solid solutions: substitution, introduction and subtraction. These varieties have certain features of the crystal structure, which determines the properties of the material.
Solid replacement solutions are formed by replacing part of the solvent atoms in its crystal lattice with atoms of the dissolved component. As a rule, this is a disordered placement, since the atoms of the dissolved element do not occupy special places in the crystal lattice, but only replace solvent atoms in random nodes.
It may also be the other way around, when the atoms of the solvent and solute elements are located in different crystallographic planes. Such solid solutions are called ordered and are characterized by higher hardness and brittleness.
The possibility of ordering the crystal lattice of solid solutions was discovered by Nikolai Semenovich Kurnakov in 1914. A Russian chemist discovered the phenomenon of ordering when studying the electrical resistance of alloys copper and gold. X-ray analysis confirmed that the change in the properties of the material is due to the redistribution of atoms within the crystal lattice. Under certain conditions, the atoms of a dissolved element can change from a chaotic distribution to an ordered one. In industry, the regulation of processes for ordering solid solutions plays a key role in production of precision alloys based gland et cobalt.
Solid embedding solutions occur when atoms of the dissolved component are embedded in the voids of the crystal lattice.
Solid subtraction solutions are formed due to the appearance of vacant nodes in the crystal lattice when one of the components of the chemical compound is dissolved.
The study of solid solutions and how to influence their structure is of fundamental importance for modern metallurgy. This knowledge makes it possible to create materials with certain physical, mechanical and chemical characteristics that will best meet the requirements of modern technologies and innovative solutions.
