Microstructure Evolution of Aluminum Deformed by Combination of KoBo Extrusion and Differential Speed Rolling (DSR)

Abstract:

In the present paper results of a microstructure examination of aluminum deformed by a two step process composed of a combination of two continuous straining methods – the KoBo extrusion and a cold rolling have been shown. The cold rolling was conducted in two variants – with an equal speed of both rolls (ESR) and with a differentiation of the upper ad the lower roll speed (a differential speed rolling – DSR). Results of a transmission electron microscopy (TEM) analysis revealed that applied processing strongly affects a microstructure of the examined material. It is shown that selected parameters of the KoBo extrusion allow obtaining a fine grained material with a grain size in the range of 1÷3 μm. Since a subsequent deformation of as KoBo extruded aluminum bars through the conventional rolling (ESR) leads to a formation of normally observed structural features (e.g. deformation bands), an application of the DSR methods results with a further grain refinement effect. It is found that, the KoBo extrusion combined with the DSR deformation allows obtaining aluminum plates that are characterized by a homogeneous structure with the grain size in the submicron range.

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