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Effect of Heterogeneous Microstructure on Refining Austenite Grain Size in Low Alloy Heavy-Gage Plate

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School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
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Colarborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China
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State Key Laboratory of Steel for Marina Equipment and Application, Anshan Steel, Anshan 114021, China
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Laboratory for Excellence in Advanced Steel Research, Department of Metallurgical and Materials Engineering, University of Texas at El Paso, El Paso, TX 79912, USA
*
Author to whom correspondence should be addressed.
Metals 2020, 10(1), 132; https://doi.org/10.3390/met10010132
Received: 18 November 2019 / Revised: 9 January 2020 / Accepted: 13 January 2020 / Published: 16 January 2020
The present work introduces the role of heterogeneous microstructure in enhancing the nucleation density of reversed austenite. It was found that the novel pre-annealing produced a heterogeneous microstructure consisting of alloying elements-enriched martensite and alloying-depleted intercritical ferrite. The shape of the martensite at the prior austenite grain boundary was equiaxed and acicular at inter-laths. The equiaxed reversed austenite had a K-S orientation with adjacent prior austenite grain, and effectively refined the prior austenite grain that it grew into. The alloying elements-enriched martensite provided additional nucleation sites to form equiaxed reversed austenite at both prior austenite grain boundaries and intragranular inter-lath boundaries during re-austenitization. It was revealed that prior austenite grain size was refined to ~12 μm by pre-annealing and quenching, while it was ~30 μm by conventional quenching. This is a practical way of refining transformation products by refining prior austenite grain size to improve the strength, ductility and low temperature toughness of heavy-gage plate steel. View Full-Text
Keywords: alloying element enrichment; heterogeneous microstructure; nucleation site; grain refinement alloying element enrichment; heterogeneous microstructure; nucleation site; grain refinement
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Yuan, S.; Xie, Z.; Wang, J.; Zhu, L.; Yan, L.; Shang, C.; Misra, R.D.K. Effect of Heterogeneous Microstructure on Refining Austenite Grain Size in Low Alloy Heavy-Gage Plate. Metals 2020, 10, 132.

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