Study on mechanism of refining and modifying in Al–Si–Mg casting alloys with adding rare earth cerium

Abstract

In this paper, Al-7%Si-0.6%Mg-X%Ce (X=0, 0.1 and 0.2) casting alloys were prepared by vacuum induction furnace. Using optical microscopy (OM), X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy spectrometry (EDS), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), the microstructures of the experimental alloys were studied, and the mechanism of refinement and modification of the alloy were discussed. Results show that AlCeSi2 was formed after adding cerium element in the Al alloy, besides those compounds of α-Al, silicon, eutectic of α-Al + Si and iron-rich phase. Furthermore, with the increase of cerium addition, α- Al dendrite arms decrease, the AlCeSi2 was formed, and the growth of iron-rich phase was hindered, respectively. Also, the areas of eutectic of α-Al + Si were decreased, due to the supercooling increasing of the alloys. In addition, the α-Al grains were refined, because existing of heterogeneous nucleation core supplied by AlCeSi2, and component supercooling caused by cerium adding. Moreover, the formation of AlCeSi2 consumed to some silicon elements, which leaded to size and amount reduction of eutectic silicon. The formation of high-density stacking fault can induce silicon modified, and the formed high-density stacking fault was produced by cerium as impurity element into silicon.

Enhancement of the Corrosion Properties of Al–10%Si–2%Cu Alloys with La Addition

“…The corrosion is mainly concentrated at the grain boundary between the intermetallic compound and matrix aluminum [ 5 , 9 ]. In research on the corrosion of aluminum with the addition of rare-earth elements, it is reported that the low potential difference between the new precipitate phase and aluminum shows a lower corrosion rate compared to the alloy without rare-earth elements and improves corrosion resistance properties [ 11 , 12 , 13 ]. However, most rare-earth elements have high costs and limited reserves, making their application to Al alloys challenging.…”