Title

Mechanical Alloying And Severe Plastic Deformation

Abstract

Recently developed methods for materials processing, such as mechanical alloying, cryomilling, friction stir processing, equal-channel angular pressing, and high-pressure torsion, are reviewed in the present chapter. Over the last two decades, there has been increasing interest on the synthesis of advanced materials using mechanical alloying, and currently this represents a vital area of research in the area of materials processing. Typically, mechanical alloying introduces repeated plastic deformation of powders via collisions with a grinding medium. Because the heavy plastic deformation introduces a high density of crystalline defects, alloy formation and microstructural evolution, especially grain size reduction, are readily attained during milling. Hot or cold isostatic pressing followed by extrusion and forging are examples of routes that are commonly used to consolidate the milled powders.Mechanically alloyed materials usually exhibit higher strength and higher creep resistance, as compared to those of equilibrium materials. As a variant of mechanical alloying, cryomilling is carried out with a slurry formed by the powder, milling balls, and a cryogenic liquid. Cryomilling results in the formation of a highly thermally stable microstructure due to the presence of nanoscale dispersions. In addition to mechanical alloying and cryomilling, this chapter covers three techniques that also belong to the family of severe plastic deformation methods: friction stir processing, equal-channel angular pressing, and highpressure torsion. Friction stir processing is a rapidly maturing, solid-state thermo-mechanical technique for modifying the near-surface microstructure. In the section on friction stir processing, microstructural evolution and two major applications are discussed; these being the defect repair of cast alloys, and its use to make a precursor for superplastic forming. During equal-channel angular pressing, the material is pressed through a die that has two channels, with an identical cross-section. Equal-channel angular pressing refines the microstructure via deformation under high-strain conditions, resulting in enhanced strength, but usually low ductility. Finally, as one of most effective methods for processing nanostructured materials, the characteristics of high-pressure torsion are briefly outlined.

Publication Date

1-1-2007

Publication Title

Materials Processing Handbook

Number of Pages

273-300

Document Type

Article; Book Chapter

Personal Identifier

scopus

Socpus ID

85056032493 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85056032493

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