Influence of Intermediate Annealing on the Nanostructure and Mechanical Properties of Pure Copper Processed by Equal Channel Angular Pressing and Cold Rolling

Abstract

The effects of intermediate heat treatment on the nanostructure and the mechanical properties of pure copper samples processed by four passes of equal channel angular pressing (ECAP) and cold rolling (CR) with a total reduction of 55 pct were investigated. The annealing treatments were done at 423 K, 463 K, and 523 K (150 °C, 190  °C and 250 °C) for 15 minutes. Microstructural examinations revealed no trace of a recrystallization after annealing at 423 K (150 °C). X-ray diffraction analysis illustrated that employing annealing treatment at 463 K (190 °C) decreased the coherent domain size and, consequently, increased the microstrain value. Moreover, nucleation of the newly formed grains resulted from discontinuous static recrystallization decreased the mean grain size. The yield and the tensile strength were also enhanced due to the reduction of the coherent domain size, the internal stress augmentation, and the presence of the new fine grains. Annealing at 523 K (250 °C) increased the fraction of the recrystallized structure and, consequently, decreased the fraction of the grains created by ECAP. As a result, the typical rolling texture intensified.