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.