OBTAINING FRAGMENTED MICRO AND NANO LEVER STRUCTURE OF THE PURE COPPER AFTER DRAWING AND ECAP

10.25712/ASTU.1811-1416.2023.03.014

Abstract

At present, it is of interest to obtain the regulated copper submicrostructure after the equal-channel angular pressing (ECAP) method. The paper shows the change in the structure of subgrains of pure copper up to 600 nm in size after severe cold plastic deformation. The purpose of this work is to show the possibility of obtaining microfragments in a regulated copper substructure at all stages of cold severe plastic deformation. To carry out the study, a bar of commercially pure copper M1 with a diameter of 20 mm was obtained after cold (T = 20 ºС) deformation by drawing (as delivered). Severe plastic deformation of the rod was carried out by the ECAP method along the route Bc through 4 and 8 passes. Images of the submicrostructure and electron diffraction patterns of the samples were obtained by transmission electron microscopy. In the primary subgrains obtained after drawing, shear first occurs with the formation of deformation defects in the form of a package of nanotwins, each 35 nm thick. Then, the accommodative slip occurs already in the bulk of the sample, after which the nanotwin packages are destroyed and rounded fragments 100 nm in size are formed. After four passes of ECAP, the fragmented reorientation microbands with a width of 70 nm and nanofragments with a width of 20 nm were found in a subgrain 500 nm in diameter. The difference between the copper substructure obtained during severe plastic deformation is that after four passes of ECAP, the reorientation microbands are present, and after eight passes of ECAP, nanofragments with a diameter of 35 nm or more are formed at the boundaries and joints of the subgrain. The reorientation microbands were formed under the action of disclinations located at the junctions and within the subgrain boundaries of the subgrain.