Effect of electrodes and thermal insulators on grain refinement by electric current pulse

The application of electric current pulse (ECP) to a solidification process refers to the immersion of electrodes into the liquid metal and the employment of thermal insulators on the upper surface of metal. In order to ascertain the effects of these two factors on the structure refinement by the ECP technique, three groups of experiments were performed with different types of electrodes or various thermal insulators. By the comparison between solidification structures under different conditions, it is followed that the electrode and the thermal insulator have an obvious influence on the grain refinement under an applied ECP, and further analysis demonstrates that the thermal conditions of the liquid surface play a vital role in the modification of solidification structure. Also, the results support the viewpoint that most of the equiaxed grains originate from the liquid surface subjected to an ECP.