Mg alloy infiltrated Si–O–C ceramic foams

Magnesium alloys reinforced with an open cell ceramic foam form interpenetrating phase composites that offer improved strength and creep resistance at elevated temperatures. Open cell polymer derived Si/SiC/Si–O–C ceramic foams were fabricated from Si/SiC loaded poly(silsesquioxane) by an in situ foaming process at 270 °C followed by pyrolysis at 1000 °C in inert atmosphere. The ceramic foams are characterized by a high interconnectivity of the foam cells and a pore diameter ranging from 0.5 to 2.0 mm. The compression strength exceeds 4 MPa at a fractional density of 27%. Interpenetrating AZ91 Mg alloy/ceramic foam composites were manufactured by squeeze casting. Interface bonding between the metal phase and the ceramic skeleton was triggered by controlled pre-oxidation annealing of the ceramic foam and gave rise for significant improvement of the crushing strength.