This study investigated the microstructure and phase formation in a Ni-Si eutectic alloy, specifically Ni-11.5 wt.% Si, under varying solidification conditions. The primary objective was to understand the influence of high cooling rates by comparing samples processed via directional solidification at low growth rates and rapid solidification using a melt-spinning technique. The Ni-Ni3Si eutectic system is known for its inherent thermal stability, making it relevant for composite material development. Experiments involved sample preparationin an electric arc furnace, followed by processing and analysis using DSC and X-ray diffraction. Results indicated that samples processed under conditions approximating equilibrium, such as low-rate directional solidification, developed a regular, aligned, and lamellar in-situ composite microstructure. In contrast, rapid solidification through melt-spinning led to the formation of an anomalous eutectic microstructure and a metastable Si-rich phase, particularly evident at the ribbon surface and within its internal regions. An increase in growth rate also correlated with a decrease in lamellar spacing.
DUTRA et al. (Fri,) studied this question.