Open Access Conference Proceedings

This study investigates advanced composite materials consisting of a NiAl matrix reinforced with an FeSi phase, which are considered promising candidates for next-generation tool applications, with the potential to replace conventional high-speed steels alloyed with tungsten and cobalt. The alloys were synthesized via vacuum induction melting followed by centrifugal casting. To further tailor their microstructure, an experimental alloy with a 1:1 mass ratio of matrix to reinforcing phase was subjected to directional solidification using the Bridgman method. The process was carried out at a temperature of 1450 °C with a holding time of 30 minutes, followed by controlled crystallization at a rate of 100 mm/h. Microstructural characterization was performed using the light optical microscopy (LOM) and scanning electron microscopy (SEM). The chemical composition was determined by energy-dispersive X-ray spectroscopy (EDX), and the microhardness was measured using the Vickers indentation method. In the as-cast state, the alloy exhibited a typical in-situ composite microstructure consisting of primary NiAl-based dendrites and interdendritic regions containing lamellar eutectic structures and discrete reinforcing phases. The eutectic structures were composed of alternating FeSi- and NiAl-based phases, while certain interdendritic areas were occupied by an FeSi-based phase with only minor Ni and Al content. Directional solidification via the Bridgman method, which enables controlled solidification through precise regulation of the temperature gradient and solidification front velocity, significantly influenced the morphology and distribution of these phases. As a result, the alloy featured a more refined, oriented, and homogeneous microstructure, which is beneficial for improving mechanical performance and structural integrity in advanced composite applications.

Keywords: Iron silicide, nickel aluminide, tool material, induction melting, directional solidification

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