In sections 1.5 and 1.6 we showed the principal possibility of improving the structure and properties of cast and deformed metal as a result of various external actions on the microheterogeneous melt. Of special significance among such actions is the treatment of a liquid metal by powerful ultrasound accompanied by the development of acoustic cavitation and acoustic flows in the metal volume. In some cases the effect of cavitation treatment of liquid aluminium alloys is much more advantageous (more rapid and more effective) than the similar effect produced by heat-time treatment (HTT) of melt.