The effect of coarse second-phase particles and fine precipitates on microstructure refinement and mechanical properties of severely deformed Al alloy

The sub-micrometer microstructure developed during severe plastic deformation by equal channel angular pressing in an Al alloy containing a small amount of dispersed intermetallic particles has been examined in material in a variety of solutionised and precipitated states. Microstructural refinement, and corresponding strengthening, occurs faster in these particle-containing materials than in particle-free equivalents. Coarse precipitate and dispersoid particles remain mostly unaffected by the severe deformation, and appear to help stabilise a finer deformation microstructure, while fine precipitates are sheared and apparently dissolved. The extent of microstructural refinement and strengthening depends more on solute content than on particle distributions. The limited effect of dispersoid and precipitate particles may be due, in part, to their presence in only small volume fractions, less than 1% by volume each. Strengthening depends more on dislocation arrangements and densities than on the number of boundaries present.