Al/Al2O3 metal matrix composites produced using magnetic field-assisted freeze-casting of porous ceramic structures

Al/Al2O3 metal matrix composites (MMCs) were produced by metal infiltration of porous ceramic preforms. The porous ceramic preforms were fabricated using the magnetic field-assisted freeze-casting method, resulting in vertically aligned porous channels. Preforms were prepared by freezing an Al2O3/Fe3O4-containing slurry within an applied magnetic field. Vertical alignment of the channels was facilitated by the magnetic response of the Fe3O4 in the slurry during the freezing process. After freezing and sublimation, the ceramic preforms were sintered and then infiltrated with molten A356 Al-based alloy. The mechanical properties of the resulting Al2O3/A356 MMCs were compared to those of bulk Al2O3, bulk Al-based alloy (A356), and porous Al2O3 preforms using micro-indentation testing. The indentation hardness and elastic moduli values of Al2O3/A356 MMCs showed good agreement with the predicted theoretical calculations. This study provides a new approach for the design of MMCs with controlled composition and improved mechanical characteristics.