THE INTERFACE IN CARBON-MAGNESIUM COMPOSITES - FIBER AND MATRIX EFFECTS

Two types of carbon fibres were incorporated into magnesium alloy matrices by squeeze casting. Mechanical testing showed that surface treatment of the fibres led to a marked increase in the interfacial shear strength and a corresponding decrease in the longitudinal tensile strength. A small amount of fine Al4C3 forms at the fibre matrix interface in simple binary Mg-Al matrices. Mg17Al12 and Mg2Si form at the interface in the Mg-Al-Si matrix: precipitation is greatly enhanced by residual stresses at the interface and many fibres are surrounded by a brittle layer leading to inferior mechanical properties.