Effects of cerium on as-cast microstructure of AZ91 magnesium alloy under different solidification rates

In order to research the different effects of Ce on as-cast microstructure of AZ91 magnesium alloy under different solidification rates, the die-cast samples with different diameters and different Ce contents were prepared, and some characteristics of as-cast microstructure were analyzed. The results showed that Ce could refine grain size, decrease the fraction of eutectic β-Mg17Al12 phase, form Al4Ce phase and decrease solid solution of Al in the α-Mg matrix, but the above behaviors of Ce would be weakened under higher solidification rate. The essential reason for Ce to affect as-cast microstructure was that the Ce and Al concentrated in the liquid phase in front of solid/liquid interface during solidification because Ce itself is difficult to solid solute in α-Mg matrix and inhibits solid solution of Al in α-Mg matrix. However, the dynamic condition of concentration of Ce, Al would be changed when solidification rate varied, resulting in different influence extents of Ce on as-cast microstructure under different solidification rates.

Graphical AbstractThe proportion and morphology of Al4Ce phase with the same Ce content are different under different solidification rates. Thus the factor of solidification rate should be considered when scientific researchers study rare earth magnesium alloyFigure optionsDownload full-size imageDownload as PowerPoint slide