Processing of Ultrafine-Grained Cu-Fe-Cr Composite by Equal Channel Angular Pressing

In this study, equal channel angular pressing was carried out on Cu-Fe-Cr composites at room temperature. The microstructure and hardness of Cu-Fe-Cr pressed using different ECAP routes were investigated. All Cu-Fe-Cr specimens showed ultrafine-grained microstructures with the shape and distribution of Fe-Cr phase dependent on the processing routes. As the number of pressing increased by route A, the initial denfrite of Fe-Cr phase were elongated along the shear direction and developed into filaments. On the other hand, as the number of pressing increased by route Bc, the initial dendrite became finer by fragmentation with no pronounced change of the shape. In route C, the shearing of the second phase in the first pass can be reversed by the shearing in the reverse direction in the second pass and the morphological change of Fe-cr particles is minimal. The hardness increased more rapidly in route Bc and route C than in route A. In ECAPed Cu-Fe-Cr, the spacing between Fe-Cr filaments did not decrease appreciably with strain unlike the cold-drawn Cu-Fe-Cr in which the spacing between Fe-Cr filaments decreases rapidly with strain. The higher strength in route C can be associated with the sub-divided microstructure resulting from the activation of various slip systems enhanced by the presence of larger strong particles. This result suggests that the microstructural development in Cu matrix is more important in strengthening than the morphological development of Fe-Cr phase in ECAPed Cu-Fe-Cr.