MICROSTRUCTURAL EFFECTS OF ULTRASONIC VIBRATIONS APPLIED DURING PLANAR FLOW CASTING OF STEELS

It is well known experimentally that the application of sound waves to undercooled melts results in grain refinement. The present state of u nderstanding of the underlying phenomena attributes the grain refineme nt to pressure waves generated by the collapse of cavities produced by the sound waves. It is also well known that rapid quenching can resul t in grain refinement down to the micrometer scale. The aim of the pre sent work was to test the feasibility of combining these two technique s to achieve greater grain refinement. We applied sound waves in the f requency range of tens of kilohertz to the melt crucible during planar flow casting of FeCr steels. The usual strips 10 mm wide were obtaine d with and without the ultrasounds, thus proving that their applicatio n does not destabilize the melt puddle. Depending on the alloy composi tion, some modifications of texture and microstructure were observed.