The effect of coarse second-phase particles on the rate of grain refinement during severe deformation processing

The effect of second-phase particles on the rate of grain refinement during severe deformation processing has been investigated, by comparing the microstructure evolution in an AA8079 aluminium alloy, containing 2.5 vol.% of similar to2 gm particles, with that in a high purity, single-phase, Al-0.13% Mg alloy, deformed identically by ECAE to an effective strain of ten. The materials were analysed by high-resolution EBSD orientation mapping, which revealed that grain refinement occurred at a dramatically higher rate in the particle-containing alloy. A submicron grain structure could be achieved by an effective strain of only five in the particle-containing alloy, compared to ten in the single-phase material. The mechanisms that contribute to this acceleration of the grain refinement process are discussed. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.