High Strength Si‐O‐C Ceramic Foams for the Reinforcement of Mg‐Alloys

Magnesium alloys are gaining interest as light weight construction elements in automotive applications. In the temperature range exceeding 100 °C Mg alloys feature low strength and stiffness. The reinforcement of cast Mg alloys using rigid ceramic foams results in a significant improvement of the strength and creep resistance at elevated temperatures. Open cell polymer derived Si‐O‐C ceramic foams were fabricated using filler loaded poly (siloxane) by an in situ foaming process at 270 °C and subsequent pyrolysis at 1000 °C in nitrogen atmosphere. A 65 wt.‐% Si/SiC blend was used as inert filler. The ceramic foams are characterised by a high interconnectivity of the foam cells and the pore diameter ranges from 0.5 mm to 2.0 mm. The compression strength exceeds 4 MPa at a fractional density of 27%. Interpenetrating Mg‐ceramic‐composites were manufactured by squeeze casting that offer improved compression strength and reduced creep rate in the temperature range above 100 °C.