The Growth of Quaternary Divorced Eutectic in Al–Ce–Si–Mg Alloys

Abstract The quaternary eutectic reaction in the Al5Ce3Si0.5Mg (wt pct) alloy, not anticipated based on existing phase diagrams and FactSage computational thermodynamic calculations, was revealed and its growth mechanism assessed, emphasizing the key role of minor additions of magnesium. The invariant transformation at 539 °C, L → α(Al) + Si + Al 2 MgSi/Al 2 Mg 2 Si + Al 78.9 Ce 5.9 Si 12.7 Mg 2.6 , generated an ultrafine morphology of near-spheroidal phases with 50–500 nm in diameter, located individually without the ordered arrangement, being characteristic for the non-coupled growth of divorced nature.