Microstructural defects in thin sheet twin roll cast aluminium alloys.

Twin roll casting is a well established industrial casting process for the production of aluminium sheet and large volumes of material are processed in this manner every year, however, most sheet is currently cast at only 6mm thick. Thin sheet (1-4 mm thick) has been cast in a number of aluminium alloys at Oxford and a detailed examination of the microstructures of these alloys has been carried out. The microstructural defects present as a result of casting at thinner gauge have been investigated these defects include surface bleeds, channel segregates, deformation segregates and inhomogeneity of grain structure. Recently downstream processing trials of some of the alloys cast at Oxford have been commenced This presentation will discuss the various defects and propose mechanisms for their formation. The effects of these various defects upon the processing of these alloys will be discussed in the light of the initial results from the processing trials.