Direct visualization of phenomena related to steel casting and solidification

Significant advances have been made the field of modeling solidification of metals and alloys but there has been a paucity of experimental methods to verify the model predictions. The reason for this has been the difficulties posed by high temperatures, containment of reactive molten metals and problems with radiation from the metal surfaces. Techniques have therefore focused upon discerning the final structure at higher and higher resolutions by electron microscopy, which often only allows a posteri observations. It is however difficult to extract information on the kinetics of process at high temperatures through these methods. Recently, thanks to technological advancements, there exists a growing array of experimental tools that allow the study high temperature solidification and crystallization processes of metal alloys and oxides in situ. This paper highlights some of the recent advances in techniques for visualizing the microstructural evolution during liquid to solid transformation in alloys and oxides. The techniques include the in situ observation methods of confocal scanning laser microscopy and the double hot thermocouple technique. Examples will be given from the solidification behavior of ferrous alloys and undercooled liquid oxides.