Abstract
Submicrocrystalline and/or nanocrystalline materials prepared by severe plastic deformation possess improved properties as compared to their coarse grained (CG) counterparts. Ultrafine-grained (UFG) copper polycrystals prepared by equal channel angular pressing (ECAP) to various strain (1, 2, 4 and 8 passes) were investigated. ECAP processing resulted in grain size reduction by a factor of about 100. TEM analysis showed that the original CG microstructure evolves from prolate bands of cells/subgrains enclosed by lamellar nonequilibrium grain boundaries towards a more equiaxed homogeneous microstructure with equilibrium grain boundaries. The influence of the microstructure on the corrosion properties in three different aggressive media, viz. 3% NaCl, 1M HCl and the standard Livingston solution was investigated by conventional potentiodynamic polarization measurements. While the general corrosion characteristics are almost unaffected by grain refinement, the corrosion damage is more homogeneous in the UFG material, which contrasts clearly localized intergranular corrosion in CG material. This is a promising property of UFG material for engineering applications.

Key words
UFG copper, ECAP, microstructure evolution, corrosion behaviour

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