Flux-assisted spreading of an Al-7 wt%Si alloy on TiC

The effect of a K-Al-F-based flux was investigated on the wettability of TiC by an Al-7 wt%Si alloy in the interval of temperatures between 660 and 900 A degrees C in Ar and in atmospheric air. Null spreading was observed without flux whereas perfect wetting was enabled by the flux in both atmospheres. The liquid flux, which provides a locally protective atmosphere by spreading on the surfaces of the substrate and eventually on the Al alloy, dissolves the aluminium oxide covering the molten alloy enabling thus direct contact between the liquid alloy and the TiC substrate. The low tensions for the solid/flux and liquid metal/flux interfaces facilitate spontaneous spreading and instantaneous wetting. Meanwhile, the flux is displaced to the lateral periphery of the substrate and to the surface of the liquid. Under the resolution of the scanning electron microscope, microstructural examination of the interfaces did not reveal reaction products. Rapid infiltration of the alloy into TiC/flux compacts, at low temperatures, correlated well with the flux-assisted spreading kinetics observed.