EBSD investigation of the grain boundary distributions in ultrafine-grained Cu and Cu–Zr polycrystals prepared by equal-channel angular pressing

Abstract

Ultrafine-grained copper and cooper–zirconium polycrystals prepared by equal-channel angular pressing following the route Bc to various strain (1, 2, 4 and 8 passes) were investigated using electron back-scatter diffraction. Equal-channel angular pressing resulted in significant grain-size reduction. The original course-grained structure evolved from prolate bands of cells/subgrains enclosed by lamellar nonequilibrium grain boundaries (after the first two passes) towards an equiaxed homogeneous microstructure with equilibrium grain boundaries (after 8 passes). Significant changes in the volume fraction and the character of grain boundaries were observed both in Cu and in Cu – Zr alloy. Pronounced evolution of twin-related boundaries (3ⁿ grain boundaries) with strain (number of ECAP passes) was found in Cu while only a weak increase of 3 and 9 grain boundaries was observed in Cu – Zr alloys.