Behavior of block boundaries during ultrasonic vibration in alkali halide crystals at temperatures 20–300°C

The behavior of block boundaries was investigated in alkali halide crystals of various orientations deformed by ultrasound at frequencies 40–73 kHz in the temperature interval 20–300°C. The specimen orientation was defined by the angle between the fourfold axis and the propagation direction of the ultrasonic wave. The initial stage of plastic deformation at room temperature is due to the generation of sources at the block boundaries in KCl and KBr, and by the heterogeneous nucleation of dislocation in NaCl and LiF. In the temperature interval 200–300°C, in NaCl and LiF dislocation multiplication begins already with the generation of sources at the block boundaries. In 30° orientation specimens the beginning of multiplication is preceded by the motion initiated by the ultrasound of sections of the block boundaries in the {1 0 0} <110> secondary glide system.Translated from Izvestiya Vysshika Uchebnykh Zavedenii, Fizika, No. 1, pp. 49–53, January, 1986.