Free Deformation of the Initial Solid Layer of some Non-ferrous Alloys

Abstract

Droplets of several non-ferrous metals and alloys were solidified on a chill plate and the shape of the bottom after cooling was measured to study the basic deformation behaviour of the initial solid skin. The shape was always parabolic. Deformation of pure metals was positive, i.e. convex towards the chill, and was found to be caused by thermo-elastic deformation after solidification. Deformation of the alloys was positive or negative, depending on the composition. Particularly-large negative deformation was observed near the eutectics of Al-Si and Bi-Sn alloys. The cause is precipitation of secondary phases of large specific volume, such as Si or Bi in supersaturated solid-solution after solidification. The findings are expected to be applicable to the understanding of surface defects in continuously-cast steel and heat transfer phenomena in the mould.