Journal of Materials Science, Vol.29, No.2, 356-365, 1994
Filamentary Preforms of Al-13 Wt-Percent Si Alloy Reinforced with TiC-Coated and Pretreated Carbon-Fibers
Filamentary preforms of aluminium-13 wt % Si alloy reinforced with TiC-coated carbon fibres were obtained by liquid metal infiltration using K2ZrF6 as wetting agent. The interfacial structure was investigated using analytical electron microscopy (TEM, SEM) and the fibre strength measured following each step of processing. The reaction between the K2ZrF6 deposit and the molten alloy is discussed on the basis of the reaction products formed at the fibre-matrix interface, which mainly consisted of fluoride compounds (K3AlF6), different zirconium-rich silicides (Si2Zr, SiZr (Al), (Al, Si)(2)Zr) and crystalline gamma-alumina. Large amounts and/or inhomogeneous distributions of the K2ZrF6 deposit should be avoided, because the massive precipitation of colonies of intermetallics around fibres is conducive for the formation of harmful aluminium carbides and favours brittle fracture of the composite. The utilization of TiC-coatings formed by the reactive chemical vapour deposition process gave satisfactory results, both in terms of composite elaboration and fibre protection during liquid infiltration.
Keywords:METAL MATRIX COMPOSITES;ALUMINUM COMPOSITE;SURFACE-TREATMENT;FIBER;CARBIDE;WETTABILITY;INTERFACE