Influence of electric field on multiplication of dislocations in alkali halide crystals while ultrasonic vibration

There are changes in dislocation structure in alkali halide crystals while the process of ultrasonic action. The character of these changes depends on strain amplitude ε0. Under the amplitude ε0 ~ 10-5-10-4 there is multiplication of dislocations. It is controlled by the work of sources in block boundaries and by multiplication from stress concentrators mainly near edges of the specimen. Electric field influences both the processes. The field influence on multiplication of dislocations at the block boundaries is more effective than the same their near the surface of the specimen. Edge dislocations and block boundaries in alkali halide crystals are carrying electric charges. Under the influence of electric field in block boundaries redistribution of charged defects takes place. Because of it probability of appearing of optimal length sources capable generating new dislocations at given ultrasound frequency increases. Specimens of 0 and 30 degrees are researched in this paper. Presence of tangent stresses in the secondary slip plains in 30 degree orientation specimens facilitates crossed slip and multiplication of dislocations. The process of multiplication in electric field was more active. In NaCl crystals in case of absence of electric field generation process was controlled by multiplication of dislocations from stress concentrators while in electric field - by work of sources in block boundaries. Stress in specimen for the beginning of dislocation multiplication corresponds to dynamical limit of fluidity and its meaning in experiments in electric field is lower than while absence of electric field. Field influences too on the character of amplitude dependence of internal friction, connected with multiplication of dislocations. In electric field this dependence begins to appear while smaller strain amplitudes. In KBr specimens in 30 degrees orientation in electric field E=1.7-106 V/m when amplitude is ε0=5.4-10-4 we observed strong increase of internal friction. By data of repeat etching after the end of experiments labyrinth structure was displayed. Labyrinth structures appear by presence of mobile dislocations capable to move not only in easy slip plains. Labyrinth structures make specimen stronger. In LiF influence of electric field on multiplication of dislocations under the action of ultrasound appeared in higher electric fields, than in KCl and NaCl. While tenseness of electric field till to E=1-106 V/m changers of internal friction connected with multiplication of dislocations in LiF specimens did not appear. While tenseness E=1-106 V/m it became quickly increased and during some seconds came to meaning much higher internal friction for the same amplitude but without electric field. In specimen LiF in electric field there was multiplication of dislocations, controlled by the work of sources in block boundaries. From the other side without electric field the sources in block boundaries did not generate dislocations; multiplication of dislocations was made by developing of slip strips from edges of specimen.