The microstructure of as thixoformed alloy A356 has been investigated by means of optical metallography and transmission electron microscopy. Inhomogeneous deformation of the Al phase during thixoforming was observed and a local cooling rate of 160 K s-1 was estimated. The high cooling rate resulted in the formation of a wide variety of intermetallic phases. Four Fe rich phases, two Mg-Si phases and one phase containing Sr were identified by selected area electron diffraction and energy dispersive X-ray analysis. Fine needle-like precipitates were observed in the Al matrix after a T6 heat treatment.
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