Alloying


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alloying

[ə′lȯi·iŋ]
(metallurgy)
The addition of a metal or alloy to another metal or alloy.

Alloying

 

the addition of alloying elements to metal melts to impart specific physical, chemical, or mechanical properties to the alloys.

Alloying was used even in antiquity (this fact is attested to by the study of silent weapons discovered in archaeological digs). The first industrial alloying experiments in Russia were conducted in the 1830’s at the Zlatoust Plant by P. P. Anosov, who developed the bases for the theory and technology of the smelting of alloy steel. Alloying acquired great industrial significance during World War I (1914–18), when large quantities of chrome-nickel, molybdenum, and other alloy steels were used in producing artillery pieces and ship armor.

Metal alloys with various properties that differ significantly from the properties of the pure metals are produced by alloying. The crystal structure and certain properties of the phases formed (such as electrical, magnetic, and thermal properties) depend on the nature of the interaction of atoms of dissimilar elements. Alloying leads to changes in the conditions of phase equilibrium as described by the structure diagram. The alloying elements together with the base element (solvent) form new phases, such as solid solutions, intermediate phases, and chemical compounds, depending on the ratio of their atomic diameters and on their electrochemical properties.

In the presence of alloying elements there is a change in the temperature of transition from one modification to another. Alloying changes the kinetics of phase transformations. Alloying elements may significantly decrease the rate of decomposition of solid solutions and, in steels, the rate of decomposition of aus-tenite and of martensite during tempering, as well as the rate of coagulation of carbides (because of a decrease in the rate of diffusion of atoms). These circumstances are widely used in the heat treatment of metals. The change in the properties of alloyed metals also results from a change in the shape, dimensions, and distribution of structural components and in the composition and state of the grain boundaries. Alloying may retard recrystal-lization processes.

Alloying is usually performed by fusion of the alloying elements with the metal to be alloyed.

The term “alloying” is also used for the introduction of foreign atoms into a solid by bombarding the surface of the solid with ions.

REFERENCES

Hume-Rothery, W. Atomnaia teoriia dlia metallurgov. Moscow, 1955. (Translated from English.)
Bochvar, A. A. Metallovedenie, 5th ed. Moscow, 1956.

R. I. ENTIN

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