TABLE OF CONTENTS An important metallurgical challenge associated with the development of direct strip casting is the need to reassess our understanding of the relationship between microstructure and properties. The casting processes involved are usually characterised by high solidification rates which often produce far-from-equilibrium microstructures. This chapter provides an overview of the factors affecting the microstructure, texture and properties in various commercially-significant alloys produced by DSC. The various methods of representing textures are outlined in Appendix B.
The heat flow in DSC is often highly directional with the maximum interfacial heat flux occurring perpendicular to the wall of the mould ( 4.5). In the absence of inoculation, the heat flow conditions favour the formation of columnar grains in as-cast strip. In twin belt and twin roll casting, a solidifying shell is produced at each mould surface; these shells coarsen by dendritic growth and eventually interact to produce the as-solidified strip (Figure 4.12). Under certain casting conditions, a central equiaxed zone may also develop which separates these columnar regions.
It was shown in Table 2.2 that casting results in the growth of dendrites parallel to certain crystallographic directions. In both pure and impure materials, flow of liquid metal parallel to the mould wall results in the deviation of the preferred growth direction of dendrites away from the maximum heat flux direction ( 2.3.3.2). This is significant as the movement of the mould wall/s relative to the melt pool is a characteristic...
