Containerless processing in the study of metallic melts and their solidification

The study of metallic melts, their physical properties, and their solidification behaviour is of relevance to understanding of fundamental principles and to metallurgical applications. Many, if not most, of these properties are extremely sensitive to contamination of the melt by impurities. Consequently, containerless processing techniques have become an important tool in the investigation of these systems. In this review, first the most frequently used containerless techniques are discussed, such as free fall facilities (drop tubes, drop towers) and levitation facilities (acoustic, electrostatic, electromagnetic) including potential applications in the microgravity environment of space. These are correlated with the research areas which make use of containerless processing. Specifically, the measurement of thermophysical properties, nucleation experiments, crystal growth, and the solidification of nonequilibrium states are discussed. In all these cases, the major emphasis is on the study of the undercooled melt which is accessible by containerless techniques because of the drastic reduction of heterogeneous surface nucleation sites.