Effect of copper electroless coatings on the interaction between a molten Al–Si–Mg alloy and coated short carbon fibres

The role of electroless copper coatings applied on short carbon fibres on the interaction between an aluminium alloy (Al–Si–Mg) and coated fibres has been studied to get useful information for the fabrication of carbon fibre reinforced aluminium matrix composites by liquid or semi-liquid processing. The conditions used for electroless were optimized to obtain a uniform and continuous layer of copper. After characterization, uncoated and Cu coated carbon fibres were mixed with AA 6061 aluminium powders, compacted and heated at temperatures from 650 to 950 °C to study the reactivity and the resulting interface. To complete this study, differential thermal analysis (DTA) were carried out on compacted mixtures of aluminium alloy powders with Cu coated and uncoated carbon fibres, applying similar thermal cycles than for the composite manufacturing. The results show an important improving of reinforcement wetting by molten matrix when copper coatings are applied, jointly with a reduction of the alloying elements microsegregation in the matrix, unlike the composites manufactured with uncoated fibres. Additional microhardness and nanoindentation tests were carried out to study the effect of the copper incorporation from the coating to the matrix on the matrix response to the ageing hardening.