Liquid Infiltration Technique Research Articles

Control of interfaces in Al-C fibre composites

The interface of Al-C fibre composite was modified by coating a silver layer on the surface of carbon fibres prior to making composites, in an attempt to improve the wettability between molten aluminium and carbon fibres during infiltration. An electroless plating technique was adopted and perfected to provide a homogeneous silver coating on the carbon fibre surface. Al-C fibre composites were prepared using a liquid infiltration technique in a vacuum. It was found that silver coating promoted the wetting between aluminium and carbon fibres, particularly with polyacrylonitrile-base carbon fibres. However, due to rapid dissolution of silver in molten aluminium, it was believed that the improved infiltration was not due to the wetting behaviour between molten aluminium and silver. The cleaning of the fibre surface and the preservation of the cleaned carbon surface with silver coating was considered to be the prime reason for the improved wettability. Interfacial reactions between aluminium and carbon fibres were observed. Amorphous carbon was found to react more with aluminium than graphitic carbon. This is believed to be because of the inertness of the graphitic basal planes.

Characterisation of interfaces in Al–Zn–Mg alloy reinforced with Sicabo fibres

The microstructure of a metal matrix composite consisting of an Al–Zn–Mg alloy reinforced with SiC coated boron fibres has been examined by electron microscopy, electron probe microanalysis, and by optical microscopy. Considerable amounts of Mg2Si phase were found to be segregated at the fibre/matrix interface. This intermetallic was not formed by a reaction between the fibre and matrix during the fabrication process, a liquid infiltration technique, but as a result of silicon impurities present as contaminants in the melt. It was concluded that the interface phase was precipitated from the metal matrix in the later stages of solidification without any nucleation role being played by the fibre. The Mg2Si phase appears to be brittle and was present in amounts likely to have a deleterious effect on the strength of the composite.MST/871

Characterisation of interfaces in Al–Zn–Mg alloy reinforced with Sicabo fibres

The microstructure of a metal matrix composite consisting of an Al–Zn–Mg alloy reinforced with SiC coated boron fibres has been examined by electron microscopy, electron probe microanalysis, and by optical microscopy. Considerable amounts of Mg2Si phase were found to be segregated at the fibre/matrix interface. This intermetallic was not formed by a reaction between the fibre and matrix during the fabrication process, a liquid infiltration technique, but as a result of silicon impurities present as contaminants in the melt. It was concluded that the interface phase was precipitated from the metal matrix in the later stages of solidification without any nucleation role being played by the fibre. The Mg2Si phase appears to be brittle and was present in amounts likely to have a deleterious effect on the strength of the composite.MST/871