Structure and composition of ternary carbides in carbon-fibre reinforced Mg-Al alloys

The characteristics of the interlayers in metal matrix composites strongly influence the materials properties. We have investigated the formation of s uch layers in carbon-fibre reinforced Mg-Al alloys, produced via a gas-pres sure melt-infiltration process. Results of high-voltage electron microscopy , high-resolution electron microscopy, selected area diffraction and electr on energy loss spectroscopy with analysis of near-edge fine structures (ELN ES) of the relevant ionization edges (Mg-L-23, Al-L-23, C-K, Mg-K and Al-K) revealed that ternary carbides of approximate composition Al2MgC2 formed a t the fibre/matrix interfaces. Analyses of ELNES point to a close relations hip in terms of crystal chemistry between the ternary carbide Al2MgC2 and t he binary carbide Al4C3. For Al2MgC2, a structure is proposed, with metal a toms in a close-packed arrangement filled with carbon atoms in octahedral a nd trigonal-bipyramidal interstices.