Microstructural and mechanical behavior of Mg/Mg2Si composite fabricated by a directional solidification system

In the present work, the effect of cooling rates on the morphology and distribution of precipitated Mg2Si reinforcement particles from a Mg-5 wt.%Si matrix fabricated through directional solidification was studied. Using directional solidification system, different cooling rates were applied to one single cast sample. In higher cooling rates, the Mg2Si precipitated in polygonal while in lower ones, it was solidified in morphology dendritically. It was shown that by decreasing cooling rate, the primary Mg2Si particles nodule counts decreased. This was attributed to chilling effect and high solidification rates imposed by the directional solidification system as well as gravity macrosegregation of particles. In terms of mechanical properties, the structures containing polygonal morphologies and finer Mg2Si particles improved tensile properties.