Complex precipitation phenomena in strip cast steels with high sulfur and copper contents

A series of three steel alloys with increasing Cu and S concentrations has been prepared by simulated direct strip casting. It was found that the rapid solidification that occurs during direct strip casting results in the formation of a high number density of fine MnS precipitates, while Cu was retained in solid solution above equilibrium concentration. Upon ageing the MnS particles were found to coarsen and increase in volume fraction, indicating that some S was retained in solid solution in the as-cast condition. Ageing also resulted in the precipitation of Cu-rich precipitates. A new method to determine precipitate composition from small-angle neutron scattering is presented. This methodology, in conjunction with atom-probe tomography, has been used to show that the composition of the Cu-rich precipitates depends on the alloy's bulk Cu content.