a metal alloy with special physical properties (magnetic, electric, thermal, or elastic) or a rare combination of physical, physicochemical, and mechanical properties; the degree to which these properties are present is largely determined by the exactness of the proportions of the constituent materials, by the absence of undesirable impurities, and the corresponding structure of the alloy. Most such alloys are based on Fe, Ni, Co, Cu, and Nb.
Many specialty alloys exhibit anomalous properties. Of particular importance are alloys exhibiting a very small change in physical parameters with changes in temperature, magnetic and electrical fields, and mechanical loads; these include Invar, elin-var, Manganin, constantan, and Perminvar. However, alloys characterized by substantial change in physical parameters with changes in external conditions are also of practical importance; these include Permalloy, Alumel, Chromel, Copel, magnetostrictive materials, alloys for springs, and bimetals for thermostats.
Specialty alloys also include superconductive alloys, alloys with given values of physical parameters (for example, Kovar, Platinite, and Fernico), alloys with various combinations of properties, and alloys that retain the required properties under the influence of corrosive agents, vibrations, electrical discharge, radiation, and high vacuum.
Specialty alloys are indispensable materials in the manufacture of parts for highly sensitive devices and apparatus, unique experimental and miniature equipment, various types of sensors, and power transformers. They are also used in the manufacture of televisions, radios, clocks, and household appliances. Specialty alloys are fundamental to progress in precision instrumentation, automation, and other technical fields. Such alloys are produced chiefly in the form of thin strips and wire and sometimes as forgings, sheets, rods, wire and strips made with more than one metal, and single crystals. In order to achieve the desired properties to the greatest degree, it is generally necessary to employ special smelting methods, deformation, special heat-treatment conditions, and qualitative surface finishing. Advanced technology is required in order to use specialty alloys effectively.