Complex heterogeneous precipitation in titanium–niobium microalloyed Al-killed HSLA steels—I. (Ti,Nb)(C,N) particles

Precipitation in Ti–Nb Al-killed microalloyed HSLA steels (Ti/N weight ratio from 4.4 to 1) was investigated in both the as-rolled and the normalised conditions using analytical electron microscopy including parallel electron energy loss spectroscopy (PEELS). An extensive formation of heterogeneousl...

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Bibliographic Details
Published in:Acta materialia 2000-09, Vol.48 (15), p.3857-3868
Main Authors: Craven, A.J, He, K, Garvie, L.A.J, Baker, T.N
Format: Article
Language:English
Subjects:
Applied sciences
Carbides/nitrides
Cross-disciplinary physics: materials science
rheology
Electron energy loss spectroscopy (EELS)
Energy dispersive X-ray analysis(EDX)
Exact sciences and technology
Materials science
Metals. Metallurgy
Microalloyed steels
Microstructure
Phase diagrams and microstructures developed by solidification and solid-solid phase transformations
Physics
Precipitation
Solid-phase precipitation
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Summary:Precipitation in Ti–Nb Al-killed microalloyed HSLA steels (Ti/N weight ratio from 4.4 to 1) was investigated in both the as-rolled and the normalised conditions using analytical electron microscopy including parallel electron energy loss spectroscopy (PEELS). An extensive formation of heterogeneously nucleated complex (Ti,Nb)(C,N) particles down to 10 nm in size was observed. The core of such a complex particle is based on TiN and has a spherical, cubic or cruciform shape. The N/(Ti+Nb) atomic ratio in the core is similar to the average value in the steel whereas the Nb/Ti ratio is much smaller than the average value and not proportional to it. Many of the cores have caps in the form of epitaxial overgrowths based on NbC. Their composition changes from Nb(C,N) to (Nb,Ti)C as the N/Ti ratio decreases. The formation of these complex particles and their detailed morphology are controlled by the processing conditions as well as the overall composition.
ISSN:1359-6454
1873-2453
DOI:10.1016/S1359-6454(00)00194-4