A Critical Evaluation of the Processing and Properties of Ultrafine-Grained Materials Produced by Intense Plastic Straining

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9625969 Langdon This research investigates processing parameters and microstructural characteristics that are associated with ultrafine grained materials, including the influence of microstructure and concurrent microstructural evolution on the mechanical properties of materials at elevated temperatures. The research employs a new processing method equal channel angular pressing (ECA) to create nanocrystalline metal alloys. Past experiments have established that metallic alloys with ultrafine grain sizes in the nanometer range have the potential for high ductilities and superplastic-like flow at relatively low temperatures. The alloy grain boundaries are generally in a nonequilibrium condition and contain a large number of extrinsic dislocations. ECA provides a capability for producing intense plastic straining that can refine the metal alloy grain size into the nanometer range. Aluminum and aluminum-based alloys and copper alloys are selected for the study because this selection allows an evaluation of the role of stacking fault energy and its effects on dislocation networks and grain boundary structure. %%% The research could lead to a new processing technique for deformation processing of nanocrystalline materials and could impact future metal alloy processing in the metal forming industries. ***