7 - Severe plastic deformation and the production of nanostructured alloys by machining

Abstract

This chapter describes the production of nanostructured materials using severe plastic deformation (SPD) inherent to machining. The SPD can be controlled, in situ, to access a range of strains, strain rates and temperatures, enabling deformation-microstructure maps to be created. By tuning the SPD parameters, various nanoscale microstructures (e.g. nanocrystalline, nano-twinned, bimodal) can be engineered; and by constraining the chip formation, bulk forms (e.g. foil, sheet and rod) with nanocrystalline and ultrafine-grained microstructures are produced. Chip formation in the presence of a superimposed modulation enables the production of nanostructured particulate with controlled shapes including fiber, equiaxed and platelet types. SPD conditions also determine the deformation history of the machined surface, enabling microstructural engineering of surfaces. These diverse nanostructuring characteristics of machining are united by their common origins in the SPD phenomena prevailing in the deformation zone. Implications for large-scale manufacturing of nanostructured alloys, optimization of SPD microstructures, and consolidation–recycling of industrial machining chips are also briefly discussed.