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

Abstract

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.

QUOKKA, the pinhole small-angle neutron scattering instrument at the OPAL Research Reactor, Australia: design, performance, operation and scientific highlights

“…QUOKKA has successfully been used to study the bulk composition of steels, for example by Dorin, Taylor et al (2016) and Dorin, Wood et al (2016a,b). By using an electromagnet at the sample position, an anisotropic scattering pattern is obtained, as shown in Fig.…”

“…By using an electromagnet at the sample position, an anisotropic scattering pattern is obtained, as shown in Fig. 12 [reproduced with minor modification from Dorin, Taylor et al (2016)], from which the magnetic signal can be calculated. The scattering between non-magnetic inclusions and the magnetic iron matrix enables the volume fraction and the size of the inclusions to be extracted.…”

“…The scattering between non-magnetic inclusions and the magnetic iron matrix enables the volume fraction and the size of the inclusions to be extracted. Dorin, Taylor et al (2016) were particularly successful in showing the complementarity of atom probe experiments with SANS.…”

“…Small-angle neutron scattering (SANS) is a well established and powerful technique used to study the structure of materials in the size range from one to several thousand nanometres. The value of the technique across this range of dimensions results in its broad application across a plethora of scientific fields; from QUOKKA's domestic user base alone this encompasses structural biology (Wood et al, 2015), soft condensed matter (FitzgGerald et al, 2014), food science , chemistry (Wang et al, 2011) and engineering (Dorin, Taylor et al, 2016).…”

Investigating nano-precipitation in a V-containing HSLA steel using small angle neutron scattering

“…Small angle neutron scattering (SANS) is generally preferred and over the past twenty years, there has been a growing interest in its use to measure the size, size distribution and volume fraction of nanoscale precipitates in various types of steel. This has included studies at room temperature on strip cast low carbon steels [37,50,51], maraging and martensitic steels [52,53], Ti and Nb-containing microalloyed steels [54][55][56][57], Nb-containing pipeline steels [58] and NbC precipitation in the austenite phase [59]. Although Oba et al [60] investigated IPP in a vanadium microalloyed steel, this was a medium-carbon grade and quantitative data on IPP in low-carbon, V-microalloyed steels have not apparently been reported.…”