5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

Traditional aluminium casting alloys are based on binary eutectic systems with additions of minor alloying elements for improved castability and mechanical properties. The increasing demand for high strength aluminium casting alloys has led to several studies of ternary eutectic aluminium alloy systems, such as Al-Si-X (X = Sn, Ge, Cu) for the formation of bulk nano/ultrafine composite microstructures. Recent research at BCAST has led to the development of a hypoeutectic quaternary Al-xCu-2.2Si-1.1Mg (x = 5, 6.6, 10.6) (wt%) alloy for high pressure die casting (HPDC), with a good combination of strength (e.g. yield strength between 219 and 276 MPa) and ductility (e.g. elongation between 3 and 7%). The resultant as-cast microstructure of these multicomponent HPDC aluminium alloys, characterised by optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), consisted of a hierarchical composite of ductile, micron-sized, dendritic -Al phase and a hard nanocrystalline eutectic mixture. This contribution presents a detailed study of the solidification behaviour of Al-Cu-Si-Mg multicomponent hypoeutectic HPDC alloys, with an emphasis on the size/morphology/volume fraction/chemical composition of each phase as a function of Cu content.