Contribution of microstructural parameters to strengthening in an ultrafine-grained Al-7% Si alloy processed by severe deformation

An Al-7% Si alloy was severely deformed by equal channel angular pressing to study the refinement of the microstructure and associated changes of mechanical properties. The initial coarse dendritic structure was broken into an elongated submicron grain/subgrain structure, with a high dislocation density and distributed fine Si particles. The Si particles in the composite are seen to induce a high dislocation density during deformation and lead to faster structural refinement than in a monolithic alloy with the same composition as the matrix. The additional strengthening of the composite relative to the monolithic alloy is due to both the finer grain size and the high retained dislocation density. Severe plastic deformation also leads to an improvement in the ductility of the strong material due to the refinement of both the matrix microstructure and the Si particles. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.