Microstructure vs. casting processes in the Fe-Si-Ca-A1 system

In this study, a systematic investigation was conducted on the phase formation within the quaternary Fe-Si-Ca-Al system to explore the non-equilibrium compound named 'caalsifer', which has been previously identified in industrial ferrosilicon alloys. The objective was to ascertain the potential domain of this non-equilibrium phase and to enhance the understanding of microstructure and phase solidification during casting processes of ferrosilicon alloys. The methodology involved laboratory experiments performed with both arc and induction fusion furnaces equipped with water-cooled copper crucibles, using compositions closely related to that of caalsifer. The materials produced were characterized chemically and compositionally through scanning electron microscopy and X-ray diffraction techniques. The results revealed a tentative relationship between microstructure and phase assemblage, indicating that the cooling rate significantly influences the formation of major phases in ferrosilicon alloys. Furthermore, the critical role of the AI:Ca weight ratio on the emergence of the caalsifer phase was established, with variations in sample mass affecting the cooling regime during solidification. This work contributes valuable insights into the casting processes of ferrosilicon alloys and the conditions leading to the formation of the caalsifer phase.