Recrystallization

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recrystallization

[rē‚krist·əl·ə′zā·shən]
(chemistry)
Repeated crystallization of a material from fresh solvent to obtain an increasingly pure product.
(crystallography)
A change in the structure of a crystal without a chemical alteration.
(metallurgy)
A process which takes place in metals and alloys following distortion and fragmentation of constituent crystals by severe mechanical deformation, in which some fragments grow at the expense of others, so that larger, strain-free grains are formed; it progresses slowly at room temperature, but is greatly speeded by annealing.
(petrology)
The formation of new mineral grains in crystalline form in a rock under the influence of metamorphic processes.

Recrystallization

 

(1) Recrystallization in the solid state is the change in the crystal structure of a substance that takes place upon heating or cooling, without a change in the state of aggregation. It is determined by the polymorphic (allotropic) transformations of the components forming the solid.

(2) Recrystallization from solutions is a process involving the dissolution of a crystalline substance with the subsequent precipitation of its crystals from the solution. It is used to remove impurities from crystalline substances.


Recrystallization

 

the process of the formation and growth, or only the growth, of single crystalline grains (crystallites) of a polycrystal at the expense of other grains of the same phase. The rate of recrystallization increases exponentially with temperature. Recrystallization is especially rapid in plastically deformed materials.

Three stages of recrystallization are distinguished: the primary stage, in which new, nondeformed crystallites are formed in the deformed material and grow by absorbing the deformed grains; the accumulative stage, in which the nondeformed grains grow at each other’s expense, as a result of which the average size of the grain increases; and secondary recrystallization, which differs from the accumulative stage in that only a few of the nondeformed grains have the capacity to grow. In the course of secondary recrystallization the structure is characterized by grains of different sizes.

Recrystallization eliminates structural defects, alters the size of the grains, and may alter the crystallographic orientation of the grains (texture). Recrystallization changes the state of a substance to one of greater thermodynamic stability. In the primary stage this change is due to a reduction in the distortions produced by the deformation, and in accumulative and secondary recrystallization it is due to a reduction in the total surface area of the boundaries between the grains. Recrystallization alters all the structurally sensitive properties of the deformed material and often restores the predeformation structure, texture, and properties. Sometimes the structure and texture after recrystallization differ from the original structure and texture and thus there is also a difference in properties.

Recrystallization is widely used in industry in metal and alloy technology to regulate the shape and size of the grains and the texture and properties of the metals and alloys.

REFERENCE

Gorelik, S. S. Rekristallizatsiia metallov i splavov. Moscow, 1967.

S. S. GORELIK

References in periodicals archive ?
Furthermore, past fires may have resulted in the recrystallisation of Fe and Al (Mataix-Solera et al.
Being subjected to the formation process (casting, rolling, recrystallisation, and heat treatment), Al and Al alloys, typical FCC ploycrystalline materials, would produce corresponding texture.
The reduction in the values of N after annealing shows that the observed crystallite size growth on annealing, for most of the samples, must be as a result of recrystallisation and coalescence of small crystallites into large ones.
The inner parts of the oncoids show a recrystallisation by xenomorphic sparitic calcite, and only occasionally an oncoid preserving remains of the original oncolitic lamination is recorded (micritized oncoids).
Almaktoum explained that the temperature of such chiller trucks must be maintained constantly as variations in temperature may result in recrystallisation, and hence growth of ice crystals.
The diagenetic processes that have affected the Arab-D reservoir include dolomitisation, leaching and recrystallisation, cementation, compaction and fracturing.Interparticle porosity is abundant in the Arab-D reservoir in the Ghawar Field and moldic porosity is common as well.
Although the quartz underwent clear recrystallisation, under the influences of temperature and stress during the orogeny (according to [91]), these changes could only account for fabric changes.
Refluxing Solvent for the Solvents used for Yield, % duration, min initiation of recrystallisation precipitation I 10-15 -- Ethanol 77 II 20 -- Ethanol 73 III 20 -- Ethanol 72 IV 30 -- Concentrated 66 acetic acid V 20 -- Isopropanol 70 VI 20 Isopropanol Isopropanol- 64 acetonitrile (4: 1 v/v) VII 20 Isopropanol Acetonitrile 57 TABLE 2: Physicochemical parameters of the CBP salts.
This may indicate an overall decrease of the organic component of the tooth, which is evidence of diagenesis, a complex set of processes that may involve the processes of dissolution, precipitation, mineral replacement, recrystallisation, and ionic substitution [35-37].
At a given temperature, development of the surface (from [S.sub.A] to [S.sub.A(B)]) may occur as a result of an increase in the number of crystallites due to a reduction in their size ([d.sub.A(B)] < [d.sub.A]) during the process of recrystallisation. All the calculations were carried out on the basis of (7a), (7b), and (9), and the results obtained are shown in Figure 2.