4 - Nanostructured Materials and Composites Prepared by Solid State Processing

Abstract

This chapter discusses the nanostructured materials and composites that are prepared by solid state processing. The solid state processing methods of mechanical attrition (MA) and mechanical alloying have been developed as a versatile alternative to other processing routes in preparing nanoscaled materials with a broad range of chemical composition and atomic structure. In this process, the lattice defects are produced within the initially single-crystalline powder particles. The internal refining process with a reduction of the average grain size by a factor of 103–104 results from the creation and self-organization of dislocation cell networks and the subsequent formation of small-angle and high-angle grain boundaries within the powder particles during the mechanical deformation process. As a consequence, changes of the thermodynamic, mechanical, and chemical properties of these materials have been observed, with the properties of nanophase materials becoming controlled by the grain size distribution and the specific atomic structure and cohesive energy of the grain or interphase boundaries. Such a transition from dislocation-controlled properties to grain boundary-controlled properties is expected for nanocrystalline materials synthesized by other methods as well.