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 ?
The following further discusses the selection of laser power parameters in the laser recrystallization process.
Deformation at very low strain rates features varied and complex recrystallization mechanisms [12, 13] and cracking behaviors [14].
Wang, "Nano cyclotetramethylene tetranitramine particles prepared by a green recrystallization process," Propellants Explosives Pyrotechnics, vol.
It should be noted that apart from the compacting of Si powders, the common issue in the above-mentioned Si powder-based approaches (SSP and hot pressing) is a need for the recrystallization of such substrates.
From a structural and performance viewpoint, Hf is similar to Zr and it can increase the recrystallization temperature and heat resistance of copper.
It's generally assumed that once the temperature reaches the baseline to the left of the recrystallization exotherm, the material has solidified and can be ejected.
[30] that a heat-setting process (between [T.sub.g] and [T.sub.m]) can be regarded as a very short annealing treatment during which some melting and recrystallization will occur for the least stable crystals as well as some crystallization of the amorphous regions.
When the ECAPed sample was rolled and annealed at higher temperature, 150[degrees]C and 300[degrees]C respectively, recrystallization took place and developed quickly.
When steel is above the recrystallization temperature, it can be shaped and formed.
Below this input, a slight decrease in the ratio was observed, indicating that the cooling rate was faster than the recrystallization rate.
Despite recrystallization, tubule walls are differentiable from the surrounding matrix and from the sparitic cement filling the inside of the tubules (Fig.
Almaktoum explained that the travel temperature must be maintained constantly as variations in temperature may result in recrystallization, and hence growth of ice crystals.