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Ferrite Formation Dynamics and Microstructure Due to Inclusion Engineering in Low-Alloy Steels by Ti2O3 and TiN Addition
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0003-0533-6729
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. (Enheten strukturer)
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. (Enheten Processer)
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2016 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, 1-15 p.Article in journal (Refereed) Epub ahead of printText
Abstract [en]

The dynamics of intragranular ferrite (IGF) formation in inclusion engineered steels with either Ti2O3 or TiN addition were investigated using in situ high temperature confocal laser scanning microscopy. Furthermore, the chemical composition of the inclusions and the final microstructure after continuous cooling transformation was investigated using electron probe microanalysis and electron backscatter diffraction, respectively. It was found 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). 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. The reason for this difference is the higher potency of the TiOx phase as nucleation sites for IGF formation compared to the TiN phase, which was supported by calculations using classical nucleation theory. The IGF fraction increases with increasing prior austenite grain size, while the fraction of IGF in both steels was the highest for the intermediate cooling rate of 70 °C/min, since competing phase transformations were avoided, the structure of the IGF was though refined with increasing cooling rate. Finally, regarding the starting temperatures of IGF and GBF, they decrease with increasing cooling rate and the starting temperature of GBF decreases with increasing grain size, while the starting temperature of IGF remains constant irrespective of grain size.

Place, publisher, year, edition, pages
Springer, 2016. 1-15 p.
Keyword [en]
Austenite, Cooling, Electron probe microanalysis, Ferrite, Grain boundaries, Grain size and shape, High strength steel, Inclusions, Microstructure, Nucleation, Titanium alloys, Titanium compounds, Titanium nitride, Classical nucleation theory, Confocal laser scanning microscopy, Continuous cooling transformation, Electron back scatter diffraction, Final microstructures, Inclusion engineering, Intra-granular ferrites, Prior austenite grain size
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-187285DOI: 10.1007/s11663-016-0630-0ISI: 000379510000008ScopusID: 2-s2.0-84959523083OAI: oai:DiVA.org:kth-187285DiVA: diva2:929532
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QC 20160519

Available from: 2016-05-19 Created: 2016-05-19 Last updated: 2016-08-15Bibliographically approved

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Mu, WangzhongHedström, PeterJönsson, Pär GöranNakajima, Keiji
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Metallurgical and materials transactions. B, process metallurgy and materials processing science
Metallurgy and Metallic Materials

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