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Open AccessFeature PaperArticle

Impact of Precipitate Morphology on the Dissolution and Grain-Coarsening Behavior of a Ti-Nb Microalloyed Linepipe Steel

1
Ferrous Physical Metallurgy Group, University of Pittsburgh, Pittsburgh, PA 15261, USA
2
United States Steel Corporation, Pittsburgh, PA 15120, USA
*
Author to whom correspondence should be addressed.
Metals 2020, 10(1), 89; https://doi.org/10.3390/met10010089
Received: 28 November 2019 / Revised: 31 December 2019 / Accepted: 1 January 2020 / Published: 4 January 2020
(This article belongs to the Special Issue High-Strength Low-Alloy Steels)
The relationship between precipitate morphology and dissolution on grain coarsening behavior was studied in two Ti-Nb microalloyed Linepipe (LP) Steels. The developed understanding highlights the importance of the complex relationship between precipitate constitutive make-up, dissolution mechanism and grain boundary (GB) pinning force. Equilibrium-based empirical solubility products were used to calculate precipitate volume fractions and compared to experimental measurements. Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction (EBSD) and Electron Probe Micro-Analysis (EPMA) were conducted on bulk samples. Transmission Electron Microscopy (TEM)-based techniques were used on C-replica extractions and thin-foils. A retardation in the grain-coarsening temperature compared to the predicted coarsening temperature based on equilibrium calculations was noticed. In addition, a consistent NbC epitaxial formation over pre-existing TiN was observed. The resulting reduction in total precipitate/matrix interface area and the low energy of the TiN/NbC interface are pointed to as responsible mechanisms for the retardation in the kinetics of precipitates’ dissolution. This dissolution retardation mechanism suggests that a lower Nb content might be effective in controlling the grain coarsening behavior of austenite. View Full-Text
Keywords: grain coarsening; precipitate dissolution; epitaxial precipitation; Ti-Nb microalloyed steel; linepipe grain coarsening; precipitate dissolution; epitaxial precipitation; Ti-Nb microalloyed steel; linepipe
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MDPI and ACS Style

Solis-Bravo, G.; Merwin, M.; Garcia, C.I. Impact of Precipitate Morphology on the Dissolution and Grain-Coarsening Behavior of a Ti-Nb Microalloyed Linepipe Steel. Metals 2020, 10, 89.

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