In Situ Observation of Semisolid Fe-2.5C-1.5Si Gray Cast Iron

Fe-2.5C-1.5Si gray cast iron evaluated in previous works exhibited promising potential as semisolid raw material presenting low levels of maximum stress and viscosity, similar to Al-Si alloys. This work is intended to investigate phase transformations and liquid phase formation for the Fe-2.5C-1.5Si gray cast iron in order to understand the performance of the alloy during the semisolid processing. Thus in situ heating experiments via high temperature laser scanning confocal microscopy were performed to analyze the solid-to-liquid transition. At room temperature alloy presented a matrix of pearlite and ferrite with type D flake graphite. During the heating process the main transformations observed were graphite precipitation on the austenite grain boundaries, graphite precipitates and flakes graphite growing and coarsening with the increasing of temperature and the beginning of melt around 1140°C. Coarsened flakes at high temperatures resulted in a liquid continuous network after melting, thereby the liquid phase was formed surrounding and wetting homogeneously the solid phase. This favors the detachment of grains from each other and leads to the intended solid globules immersed in liquid.