Relaxation processes during high-frequency mechanical loading of metals deformed at low temperatures

Abstract

Experimental data on the influence of high-frequency (∼20 kHz) mechanical loading (exposure to ultrasound) on hcp and bcc metals that have been pre-deformed under cryogenic conditions are generalized and analyzed. It is shown that under exposure to ultrasound, the energy of the mechanical oscillations is predominantly dissipated at the boundaries of twins and that this determines the processes for redistribution of dislocations in accommodation zones of twinning layers and in the matrix, while ensuring relaxation of internal stresses at these sites. The efficiency of twin boundaries as stress concentrators is balanced and this reduces the cold brittleness of metals and enhances the contribution of polygonization processes during subsequent annealing, thereby delaying recrystallization. These results substantiate ultrasonic irradiation as an analog of local thermal activation and as a method for regulating the degree of conjugation of phase-matrix interfaces.