CONTROLLED SOLIDIFICATION OF METAL MATRIX COMPOSITES UTILISING MONOVARIANT EUTECTIC REACTIONS

The application of monovariant eutectic reactions to the preparation of metal matrix composites is discussed. As is well-known, this class of reactions leads to structures similar to those of an invariant binary eutectic reaction, since in both cases two solid phases precipitate simultaneously from a liquid. In the case of monovariant eutectics, however, one of these phases is a solid solution. The composition of this solid solution may be varied within wide limits, and a substantial influence on the properties of the matrix and the morphology of the fibres is therefore possible. As examples, the systems Ag/Au/Si and C/Cr/Ni/Si are used. The former, which has a monovariant ternary eutectic as its only constitutional feature, serves well as a simple demonstration model. In the C/Cr/Ni/Si system, strengthening of a Cr/Ni/Si matrix (82.25 wt % Ni/11.00 wt % Cr/6.35 wt % Si) by 22 vol % Cr3C2 could be achieved by directional solidification. © 1969 Chapman and Hall.