On the processing of hetero-nanostructured metals for improved strength/ductility balance by ECAE and SPS techniques

Abstract

This paper has examined some recent findings concerning the processing of fully dense hetero-nanostructured materials (i.e. consisting of nano, ultrafine and micrometric grains) which can be produced by using the interplay between heavy deformation and recrystallization. By plastic deformation of bulk materials, an improved strength/ductility balance can be obtained directly by imparting high strain deformation (by equal channel angular extrusion) until the occurrence of recrystallization. Using a powder metallurgy route, the strong potential of electric field assisted sintering (ECAS) techniques for producing multi-scale microstructures when a conducting milled powder is used is demonstrated. In this case, in addition to modify the classic processing parameters (time/temperature of spark plasma sintering), altering the nature of the milled powder – by Y 2O 3 addition during the milling stage – is also a good way to delay the onset of recrystallization and, thereby, increase the fraction of ultrafine grains.