The deformation of the chill in experiments to determine the interfacial heat transfer coefficient during casting solidification

Interfacial heat transfer coefficients during casting solidification are often measured in experiments in which unidirectional heat transfer is assumed. Finite element modelling of the chill in these experiments has shown that the chill surface deforms elastically into a convex shape, the extent of which generally decreases with time. Examples from several different unidirectional solidification experiments are given. The deformation of the chill surface was also calculated with the assumption of nonuniform temperature boundary conditions. The deformation of the chill could be such that only in the central region of the casting-chill interface would the two surfaces be in contact, with a localised gap between them at their periphery. The extent of this deformation could be sufficient that heat transfer through the interface may not be unidirectional as assumed in the experiment and, depending on the location of the thermocouples placed close to the interface, the accuracy of the heat transfer coefficients calculated from the data collected at these points may therefore be affected.