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Nanostructuring Metallic Materials by Severe Plastic Deformation Methods

 Nanostructuring Metallic Materials by Severe Plastic Deformation Methods
J. M. Cabrera
Universidad Politécnica de Cataluña, Dept Ciencia de Materiales e Ing. Metalúrgica,
EEBE- c/Eduard Maristany 10-14, 08017 - Barcelona, Spain.

8 June 2018, meeting room B-607 at 2:30 p.m.

Keywords: nanostructured metals, severe plastic deformation, steel, copper, titanium

Severe plastic deformation techniques have become a mature metal processing method able to produce nanostructured metals in massive amounts. It is well known that heavy deformation can result in significant refinement of microstructure at low temperatures. However, the amount of material or the structures formed shows diverse disadvantages. Particularly final structures are usually substructures of a cellular type having boundaries with low angle misorientation, and the thickness of final products may limit their applicability. Nevertheless, the nanostructures formed from SPD are ultra fine-grained structures of a granular type containing mainly high angle grain boundaries, and certain SPD methods, such as Equal Channel Angular Pressing (ECAP) can produce large amount of materials, i.e. bulk materials without heavy limitation in dimensions.

Methods of severe plastic deformation should follow some requirements: First, it is important to obtain ultra fine-grained structures with prevailing high-angle grain boundaries. Second, the formation of nanostructures uniform within the whole volume of a sample is necessary for providing stable properties of the processed materials. And third, samples should not have any mechanical damage or cracks. Traditional methods of severe plastic deformation, such as rolling, drawing or extrusion cannot meet these requirements.

It has been pointed out the mechanical benefits obtained in materials undergoing SPD: significant increments in strength keeping acceptable ductility. From that point of view, a very interesting way to increase mechanical properties is offered. No heat treatments of alloying elements must be introduced into the original material. However, the industrials application where the nanostructured bulk metals are called to play a major role are those related with bi- or multi-functionality of a given material, that is, to increase mechanical properties without penalty on other characteristics (such us physical properties, biocompatibility, forming capacity or weldability).

Present work is devoted to summarize some possibilities that the ECAP technique offers to researchers and engineers, and to show three examples of industrial application of the latter SPD technique, namely, an electrolytic copper for power cables with high mechanical properties and high electrical conductivity, pure titanium as a high strength biomaterial, and very low carbon steel of high strength and high weldability

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