Physical modifying effects and their influence on the crystallization of casting alloys

Abstract

Basic theoretical propositions on physical modifying effects (vibration, ultrasonic, electromagnetic agitation, and thermal-temporal processing) on the crystallization of casting alloys are generalized. Mathematical calculations and experimental investigations have revealed that the crystallization and structure formation of casting alloys could be largely determined by the treatment technology using the physical effects during melting and casting. The physical effects on a crystallizing melt cause its strong turbulization and agitation, thereby decreasing the temperature and concentration gradients in the melt, eliminating overheating the liquid phase with respect to the solidus temperature, and breaking off dendrites (which are good crystallization seeds for overall melt volume). The evaluation of the dendrite growth during crystallization showed that splitting the dendrite grains is opposed to their coarsening under physical effects. The physical effects result in bulk crystallization with equiaxed grains without the formation of the columnar structure. The physical modifying effects promote the improvement of the quality of acquired alloys and casts made of them under the conditions of their rational application.