Ferrite Formation Dynamics and Microstructures in Inclusion Engineered Steels with Ti2O3 and TiN Additions
(English)Manuscript (preprint) (Other academic)
The dynamics of intragranular ferrite (IGF) formation in inclusion engineered steels with Ti2O3 and TiN additions were investigated using in-situ high temperature confocal laser scanning microscopy (CLSM). Furthermore, the chemical composition of the inclusions and the final microstructures after continuous cooling was investigated using electron probe microanalysis (EPMA) and electron backscatter diffraction (EBSD), respectively. The results show that there is a significant effect of the chemical composition of the inclusions, the cooling rate and the prior austenite grain size on the phase fractions and the starting temperatures of IGF and grain boundary ferrite (GBF) formation. The fraction of IGF is larger in the steel with Ti2O3 addition compared to the steel with TiN addition after the same thermal cycle has been imposed. This is because the TiOx phase provides more potent nucleation sites for IGF than the TiN phase does. The fraction of IGF in the steels was highest after at an intermediate cooling rate of 70 ºC/min since competing phase transformations were avoided, however, the IGF was refined with increasing cooling rate. In addition, the IGF fraction increases and the starting temperature of GBF decreases with the increasing prior austenite grain size, however, the starting temperature of IGF keeps almost the value when the grain size changes.
in situ confocal laser scanning microscopy (CLSM); intragranular ferrite; Ti-oxide; TiN; inclusion engineering; steels; phase transformation.
Metallurgy and Metallic Materials
IdentifiersURN: urn:nbn:se:kth:diva-162283OAI: oai:DiVA.org:kth-162283DiVA: diva2:797688
QS 20152015-03-242015-03-242015-03-25Bibliographically approved