Cooling slope casting to obtain thixotropic feedstock II: observations with A356 alloy

New Rheocasting (NRC) is a recently developed semisolid processing route. There are two versions of this route. In one, molten alloy is poured directly into a mould and through careful temperature control during cooling a spheroidal semisolid microstructure is achieved, before the material in the mould is upended into a shot sleeve and hence forced into a die. Alternatively, the molten alloy is poured onto a cooling slope and thence into a mould before processing. The aim of the work described in this paper, and its companion, was to develop the understanding of the microstructural development during the initial stages of this process, i.e. in the mould before processing and with the cooling slope/mould combination. In the previous paper, an analogue system based on aqueous ammonium chloride has been used to visualise what happens when an alloy is poured into a tilted mould with a chill wall, which acts to mimic the mould and the cooling slope in the NRC process. In this companion paper, the results for pouring A356 aluminium alloy directly into a mould, and also via a cooling slope into a mould, are presented.