The preparation of aligned composite materials by unidirectional solid-state decomposition

Abstract

Analogous to the alignment of lamellar eutectic structures by means of unidirectional solidification, the discontinuous decomposition of eutectoids and supersaturated solid solutions appears to yield aligned lamellar specimens under unidirectional cooling conditions. Experiments are described'concerning the eutectoids in the systems Co-Si, Cu-Al, Cu-In and Ni-In and the supersaturated solid solution of Sn in Pb. The lamellae occurring upon decomposition are parallel to the temperature gradient throughout the samples and parallel to each other over lengths of mm (Co-Si, Ni-In, Cu-Al, Pb-Sn) or cm (Cu-In). For the eutectoid decomposition of Co 3Si the experimental relationship between the interlamellar spacing λ (varying between 0.1 and 1 μm) and the decomposition rate R appears to be λ 4 R = constant. At relatively high rates (depending on the system) the parallelism of the lamellae is lost.