ABSTRACT
This chapter describes two related novel methods for grain refinement and the cheap fabrication of intermetallic compounds, named ‘duplex casting’ and ‘synthesis casting’, respectively, with the term ‘step casting’ encompassing both techniques. It presents a number of examples illustrating the benefits of step casting, including the refinement of primary aluminium in hypoeutectic Al–Fe alloys, the refinement of primary silicon in hypereutectic Al–Si alloys, and the simultaneous use of duplex casting and inoculants to grain refine a hypereutectic Al–Si alloy. The joining of NiAl to structural materials such as carbon steels, stainless steels and superalloys has been tried using synthesis casting. In step casting, one liquid is poured into a mould and a second liquid is subsequently poured into the mould during solidification of the first liquid. In duplex casting, refinement of the primary phase is enhanced by controlling the combination of liquidus temperatures of the two liquids and by increasing the cooling rate.
