Bulk Ultrasonic Treatment of Crystalline Materials

Ultrasound is widely used in the treatment of materials. Its applications in melt processing, surface hardening or finishing, metal forming, welding, etc., are well known and have been reviewed in numerous review articles and books. Among ultrasound-assisted processes, the direct action of ultrasonic waves on the structure and properties of bulk materials is of special interest. Ultrasonic waves induce oscillating shear stresses in materials which exert mechanical forces on crystal lattice defects, primarily on dislocations, which can yield a number of interesting effects on the structure and properties of crystals. The present paper aims to review studies on the effects of ultrasonic treatment (UST) on crystalline materials. First, the methods for the excitation of standing ultrasonic waves in bulk samples of materials are analyzed. Then, early studies on the effect of UST on the dislocation structure and phase composition, hardness and strength of materials with different initial structures are analyzed. An emphasis is then made on the influence of UST on the structure and mechanical properties of advanced ultrafine-grained (UFG) metals and alloys processed by severe plastic deformation (SPD). The results of simulations of ultrasound's effect on the dislocation and atomic structures of materials by dislocation and molecular dynamics methods are also reviewed.