Microstructural evolution and mechanical properties of Cu-Al alloys subjected to equal channel angular pressing

Ultrafine-grained (UFG) or nanocrystalline (NC) Cu-Al alloys were prepared using equal-channel angular pressing (ECAP) to investigate the influence of stacking fault energy (SFE) oil the microstructural evolution during deformation and the corresponding mechanical properties. The gain refinement mechanism Was gradually transformed from dislocation Subdivision to twin fragmentation by tailoring the SFE of alloys. Meanwhile, homogeneous microstructures and nanoscale grains were readily achieved in the low-SFE Cu-Al alloys and the equilibrium grain size was decreased by lowering the SFE. Moreover, in the Cu-Al alloy with extremely low SFE, shear fracture occurred during ECAP at strain levels higher than two due to the formation of macroscopic shear bands. In addition, the normalized deformation conditions at large strain were qualitatively discussed. More significantly, the strength and uniform elongation were simultaneously improved by lowering the SFE. This Simultaneity results from the formation of profuse deformation twins and microscale shear bands, and their extensive intersections. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.