Interlayer structure of carbon fibre reinforced aluminium wires

As the extent of the interfacial reactions controls the properties of metal matrix composites, the microstructural features and the chemical compositi on of the interlayers in aluminium wires reinforced with unidirectional car bon fibres (volume fraction app. 55%) have been investigated. High voltage and high resolution transmission electron microscopy of fibres, matrix, and interlayers, combined with analytical methods (electron energy loss spectr oscopy and energy filtered microscopy) revealed a nanometre-sized C/Al inte rdiffusion layer and aluminium carbide needles or platelets of 10-50 nm thi ckness and 50-500 nm length in the matrix material, starting from the inter layer, the extension of which strongly correlates with the duration of melt contact. The observed interlayer phenomena impose restrictions to the proc ess parameters, as by massive interface reactions the fibre strength is deg raded, and the formation of brittle reaction products such as Al4C3 provide s sites for initiation of fibre cracking and can cause composite failure. W ith a newly developed continuous process, which is capable of infiltrating endless products, the fibre/melt contact duration could be reduced to less than one second resulting in carbide formation lower than 0.2 wt% as confir med by chemical analyses. So it was possible to achieve strength values of the composite wires that are as high as the theoretical prediction. (C) 200 0 Kluwer Academic Publishers.