Abstract
Recent experiments resolved nucleation and growth of graphite during solidification of ductile cast iron in 4D using synchrotron X-ray tomography. A numerical model for microstructure formation during solidification is compared with the experiments. Despite very good overall agreement between observations of spheroidal graphite growth and model results, significant deviations exist towards the end of solidification. We use the experimental observations to analyse the relation between graphite growth rate and the state of the particle neighbourhood to pinpoint possible links between growth rate of individual graphite spheres and the overall solidification state. With this insight we revisit existing models for growth of spheroidal graphite and discuss possible modifications in order to correctly describe the critical final stage of solidification.
Highlights
Cast iron is a family of materials that has been in use for engineering purposes for thousands of years, and today cast iron is essential to modern society
To gain insight into the relations between process conditions and microstructural evolution during solidification of ductile cast iron (DCI) an experiment was conducted on the I12 beam line at the Diamond Light Source synchrotron facility: A cylindrical sample of 2 mm in diameter and 8 mm in length was machined from a DCI casting with 3.6 wt% C, 1.9 wt% Si and 0.07 wt% Mg
Observations on spheroidal graphite growth from in situ observations obtained by synchrotron X-ray tomography have been presented
Summary
Cast iron is a family of materials that has been in use for engineering purposes for thousands of years, and today cast iron is essential to modern society. Compared with experimentally measured temperatures and nodule size distributions it has been shown that such a solidification model underestimates the nodule number density after solidification is complete It has been speculated this is related to an inaccurate description of the nucleation and growth conditions at the end of solidification [5,6]. It is the aim of the present paper to use results from recent experimental investigations into graphite growth and the resulting microstructure with the purpose of increasing the understanding of the factors influencing growth.
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