Severe plastic deformation

PLASTIC DEFORMATION. When a metal or other solid is plastically deformed it suffers a permanent change of shape. The theory of plastic deformation in crystalline solids such as metals is complicated but well advanced. Metals are unique among solids in their ability to undergo severe plastic deformation. The observed yield stresses of single crystals are often 10 4 times smaller than the theoretical strengths of perfect crystals. The fact that actual metal crystals are so easily deformed has been attributed to the presence of lattice defects inside the crystals. The most important type of defect is the dislocation. See also Creep (Metals) Crystal and Hot Working. 

Morris, D. G. Munoz-Morris, M. A. Relationships between mechanical properties, grain size, and grain boundary parameters in nanomaterials prepared by severe plastic deformation, by electrodeposition and by powder metallurgy methods. J. Metastable Nanocrystal. Mater. 15-16, 585-590 (2003). 

The top-down approach starts with a bulk material and attempts to break it down into nanoscaled materials through physical methods. Hence, most of these techniques are really forms of fabrication rather than synthesis. For nanostructured bulk phases, including powders, the common methods are milling, devitrification of metallic glass, and severe plastic deformation. For nanocrystalline thin films (films with nanosized crystallites), methods include thermal vaporization (under high vacuum), laser ablation, and sputtering (thermal plasma), all of which were... 

Other top-down methods are used for the production of ultrafine-grained (UFG) metals and alloys. These include the devitrification of metallic glass and severe plastic deformation, in which a coarse-grained poly crystalline metal or alloy is subjected to large shear strains under pressure, forcing the grains to subdivide into nanosized... 

For practical applications, the synthesis process is a crucial step since large quantities will have to be produced reliably and at low cost. Therefore, more research is needed into new methods of synthesis, particularly for nanomaterials. In this respect, severe plastic deformation techniques could be an option but more thought has to be given to scaling up ball milling. 

Allan, B.S., ed. (2006) Severe plastic deformation toward bulk production of nanostructured materials. Nova Science, New York, p. 612. 

From the foregoing is clear that the material directly under the indenter consists of a zone of severe plastic deformation. It is known that macroscopic yielding of a crystalline polymer involves a local irreversible mechanism of fracture of original lamellae into smaller units (Grubb Keller, 1980). The heat generated during... 

D.Lesuer, C.K.Syn, O.D.Sherby. In Investigations and Applications of Severe Plastic deformation. NATO Science Series. Series 3, High Technology, V.80, Kluwer Academic Publishers, Netherlands, 2000, pp. 357-366... 

NANOSTRUCTURED MATERIALS PRODUCED BY SEVERE PLASTIC DEFORMATION... 

Abstract Severe plastic deformation of metals leads to an extremely fine... 

Key words Severe plastic deformation, strain path, fragmentation, geometric recovery, strain efficiency, equivalent strain... 

Nanostructured materials produced by severe plastic deformation... 

Key words severe plastic deformation, bulk nanostructured materials, strength and ductility... 

High pressure torsion (HPT) (Fig. la) and equal-channel angular (ECA) pressing (Fig. lb) refer to the techniques which were used in pioneer works devoted to UFG structures formation in metals and alloys [11,12] by severe plastic deformation. These methods have been further developed lately. 

Figure 1. Principles of severe plastic deformation techniques a - high pressure torsion, b - ECA pressing.

Investigations and Applications of Severe Plastic Deformation (Eds. T.C. Lowe and R.Z. Valiev), NATO Science Series 3. High technology, Vol. 80, Kluwer, Dordrecht, Netherlands, 2000. 

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