Effects of intensive forced melt convection on the mechanical properties of Fe containing Al–Si based alloys

The pickup of impurity Fe is an inherent engineering problem for the recycling of aluminium alloys, due to the detrimental effects of Fe containing intermetallic compounds on the mechanical properties. This work aims to understand the effects of intensive forced melt convection and alloying on the mechanical properties of Fe containing Al–Si based cast alloys. Varied Fe levels were introduced into widely used commercial Al–Si based cast alloys with different Mn contents. The role of intensive forced melt convection was investigated through comparative study of the microstructure properties relationship of alloys that are processed via rheo-diecasting (RDC) and conventional high-pressure diecasting (HPDC), with the former involving intensively shearing the melt in a slurry maker before diecasting. CALPHAD modelling of the thermodynamic properties of the multi-component alloys was carried out to clarify the role of alloying elements on the formation of different primary Fe containing intermetallic compounds. The experimental results show that intensive forced melt convection during solidification promotes the formation of α-AlFeMnSi compound with a compact morphology. It was also found that Mn as an alloying element assists the conversion of needle-shaped β-AlFeSi compound into more compact α-AlFeMnSi compound.