Consolidation of Particles by Severe Plastic Deformation: Mechanism and Applications in Processing Bulk Ultrafine and Nanostructured Alloys and Composites

Severe plastic deformation (SPD) can be used to consolidate particles into bulk ultrafine and nanostructured materials. SPD consolidation relies on plastic deformation of individual particles, rather than diffusion, to achieve bonding and thus can be carried out at much lower temperatures. Using examples of consolidation of Al particles by back pressure equal channel angular pressing (BP-ECAP), it is demonstrated that full consolidation is achieved when the particles are sheared to disrupt the surface oxide layer whereas consolidation is impossible or incomplete in the case of particles sliding over each other. The effects of particle characteristics such as size, shape, strength and surface condition, as well as processing parameters including temperature and back pressure, are discussed to shed light on the mechanism of SPD consolidation. Potential applications of SPD in powder consolidation and processing of bulk ultrafine and nanostructured materials are discussed.