Microstructure and mechanical properties of in situ Mg2Si/AZ91D composites through incorporating fly ash cenospheres

5 wt.% of fly ash cenospheres with average size of 100 μm were added to the molten AZ91D magnesium alloy to prepare in situ Mg2Si/AZ91D composites by means of compo-casting. The effect of the isothermal temperature and time of the composite slurry (the melt containing fly ash cenospheres) on the microstructure and mechanical properties of the composites was investigated. The effect of the solution treatment at 420 °C on the morphology of Mg2Si particles in the composites was discussed. The results showed that compared with the matrix alloy, the tensile strength of the composites was higher at both room temperature and 150 °C. After the solution treatment, the shape of Mg2Si particle transformed from the Chinese script Mg2Si to spherical, and the tensile strength of the composites was further improved.

► In situ Mg2Si phases were formed by adding fly ash cenospheres (FAC) into AZ91D.
► The sedimentable dynamic model of the FAC in molten AZ91D was described.
► The shape of Mg2Si particle tended to spherical after the solution treatment.
► Mg2Si/AZ91D composite studied had better elevated temperature tensile strength.