Walcowanie cynku w warunkach cyklicznie zmiennego stanu naprężeń ściskających

In this paper, the possibility of applying Severe Plastic Deformation (SPD) procedures in the production of flat metallic elements, such as sheet metals, tapes or flat bars, is being discussed. It focuses on methods involving dynamic changes of deformation path, particularly on a well-known KOBO method and on a recently developed process of complex, complex rolling (CR), conducted under the conditions of triple-axial, changing compressive stress. During the experiment carried out for this paper, flat bars made from a model material of zinc alloyed with 0,015wt.% aluminum were used. The addition of aluminum was aimed at reducing the activity of structural renovation of zinc, i.e., its recovery and recrystallization taken place as a result of the natural phenomenon of temperature rise accompanying severe plastic deformation processes. The flat bars were obtained via low-temperature KOBO extrusion with a side outflow. They were subjected to complex rolling, consisting of subsequent rolling, upsetting, cyclic shearing and extrusion, carried out as a single pass. It was established that flat bars obtained in this way were not breaking (cracking), unlike after conventional rolling. Moreover, it has been proved that the higher the set compression, the lower the flat bars’ hardness, although it was still higher than before complex rolling. On the other hand, the structure of flat bars obtained as a result of this procedure is highly fibrous and has sporadically occurring new, individual grains, the number of which rises with the increase of compression degree.