AbstractA mathematical model has been devised for the calculation of the heat flux from a cast cylindrical body to a metal chill during solidification. The model is based on the temperature measured in the chill close to the casting/chill interface. The heat flux as a function of time was determined for Al–Si alloys having different contents of alloying element and for chills with different initial temperatures. It was found that an increased silicon content as well as rising initial chill temperature cause a reduction in the heat flux. A further mathematical model is presented, for the calculation of the temperature field during solidification as a function of the heat flux and the thermophysical properties of the cast material, which in turn are functions of the temperature. This model yields the temperature in the casting as a function of the distance from the chill, in good approximation to the temperature actually measured in the casting. In addition, the local solidification time is obtained as a function of the distance from the chill. From metallographic specimens taken along the axis of the cylinder at specified distances from the chill, the mean dendritic arm spacingλwas calculated. It was found that the relationship betweenλand the local solidification time is given by the equationλ= ASitf0·43, where ASiis a constant which varies inversely with the solute content.MST/313