Intensification of the process of equal channel angular pressing using ultrasonic vibrations

The work presents a new method of equal channel angular pressing (ECAP) using powerful ultrasonic vibrations (UV). The authors have developed an original device of ultrasonic ECAP, in which the waveguide with the matrix are made as a single unit, and the waveguide fastening elements are located in the nodal plane of mechanical displacements of the standing wave, the excitation of which occurs directly in the matrix and the blank during pressing. For the first time, it has been proposed to transmit ultrasonic vibrations to the zone of intersection of the matrix channels through which the blank moves, not through the punch, but by exciting vibrations in the matrix itself, i. e. the matrix is simultaneously a waveguide for longitudinal ultrasonic vibrations. This allowed increasing repeatedly the efficiency of ultrasonic action by reducing the friction forces between the surface of the blank and the surface of the matrix channels, as well as by reducing the deformation forces in the zone of intersection of the matrix channels, where a simple shift of the deformed metal occurs. As a result, in comparison with the known methods of ultrasonic ECAP, when the reduction in pressing force is less than 15 %, the excitation of ultrasonic vibrations directly in the waveguide – matrix allowed reducing the pressing force by 1.5–4 times. At the same time, the structure of the pressed materials also changes significantly: the grain size and their crystallographic orientations decrease, the microhardness increases. Changes in the phase composition for all samples produced by ECAP with ultrasonic vibrations, and by conventional technology are not observed.