Al–9.00 Si–0.25 Mg alloys modified by ytterbium

摘要

The effects of ytterbium(Yb) on microstructure and solidification behavior of Al-9.00%Si-0.25%Mg alloys were investigated.By optical microscope(OM) and scanning electron microscopy(SEM),it is found that the morphology of eutectic silicon changes from coarse plates to fine fibers by the addition of 0.7%wt Yb.In addition,the grains of α-Al matrix are refined by Yb addition.Phase constitution of the alloy was analyzed by X-ray diffractometer(XRD) and energy dispersive spectroscopy(EDS)attached with SEM and mechanical properties were measured by hardness test.It is concluded that the Yb atoms are incorporated into the silicon by the adsorption at the solid-liquid growth front to cause the modification of eutectic silicon.Furthermore,the results of XRD and EDS analysis reveal that the Yb-containing phase forming in the alloys is Al_3Yb.