Development of fine grained structures using severe plastic deformation

Severe plastic deformation provides a processing tool for introducing fine grain sizes into polycrystalline materials. This paper describes the principles of equal channel angular pressing (ECAP) in which a material is pressed through a die where two channels form an L shaped configuration. The process of ECAP imposes a severe strain on the sample but there is no concomitant change in the cross-sectional dimensions so that repetitive pressings may be undertaken to achieve very high total strains. Several factors influence the nature of the microstructures attained in ECAP including the processing route by which the sample is rotated between consecutive pressings, the angle subtended by the two channels within the die, and the speed and temperature associated with the pressing. These various factors are described for a series of experiments conducted on samples of pure aluminium.