Journal of Crystal Growth 198/199 (1999) 844—849 Microstructure of Ni—Ni  Si eutectic alloy produced by directional solidification Rubens Caram*, Srdjan Milenkovic State University of Campinas, C.P. 6122, 13083-970, Campinas-SP Brazil Abstract The microstructures and solidification behaviour of Ni—Ni  Si eutectic composite have been studied systematically. Samples were processed in a Bridgman type solidification furnace using induction heating with growth rates ranging from 6.5 to 20.0 mm/h. During directional solidification, Ni—Ni  Si eutectic is characterised by cell and dendrite—free and well-aligned lamellar structure on a micron scale. The scaling laws of the variation in lamellar spacing () with growth rate (») are quantitatively developed. Despite the presence of an intermetallic phase, highly regular structure was obtained and no lamellar spacing selection problem was observed.  1999 Elsevier Science B.V. All rights reserved. Keywords: Directional solidification; Eutectic growth; Lamellar microstructure 1. Introduction The galloping industrial and technological devel- opment has induced an extensive search for the advanced materials for high-temperature applica- tions. Among a wide variety of materials, com- posite materials seem to have the greatest potential to meet ever increasing requirements [1]. A subset of this class of materials is natural or in situ composites. They can be produced, besides the con- ventional methods, by directional solidification of eutectic alloys. The advantages of this technique * Corresponding author. Tel.: #55 19 788 79 66; fax: #55 19 2893722; e-mail: caram@fem.unicamp.br. over the conventional one are manifest: it involves the extension of a well established technology, allows components to be produced from the melt in a single stage process, and leads to a composite of phases that are thermodynamically stable, chemic- ally compatible, well aligned and finely dispersed. Thus, directional solidification has received con- siderable attention in the past few decades. In the 1960s, directional solidification was developed to process eutectic alloys [2—5]. Research was initially focused on materials for high temperature struc- tural applications, but it was soon broadened to non-structural materials for electronic, magnetic, and optical applications [6]. The vast majority of technically important eutec- tic alloys are composed of two phases. Directional solidification of binary or pseudo-binary eutectics, 0022-0248/99/$ — see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 0 2 4 8 ( 9 8 ) 0 1 1 4 3 - 9