Production analysis of new machining-based deformation processes for nanostructured materials.

Abstract

Nanostructured materials, composed of sub-micron sized grains (crystals), show novel attributes not commonly found in their microcrystalline counterparts. Furthermore, these attributes can be varied by changing the grain size. Nanostructured solids have high hardness, strength and ductility; and interesting electrical and magnetic properties. Superplasticity has been observed at relatively low temperatures in some of these materials [1]. Many new and exciting applications of these materials have been sought; however, the cost of creating these materials, frequently quoted in excess of three hundred euros per kilogram [2], and an inability to make these on a large-scale with reproducible properties have restricted their broad application. We describe new machining-based manufacturing processes for making nanostructured alloys that are likely to be much less expensive. These processes are structured around chip formation by large-strain machining. It has been found that chips of a variety of metals and alloys produced during normal machining operations are composed entirely of nanocrystalline and/or ultrafine grained (UFG) structures of high hardness and strength [3-5]. Furthermore, by imposing a constraint to the chip at the point of its formation, it is feasible to produce nanostructured metals and alloys directly in bulk forms (e.g., sheet, bar, foil); the constrained chip formation process is called large-strain extrusion machining [6].