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Title: Influence of cooling rate on the precipitation behavior in Ti–Nb–Mo microalloyed steels during continuous cooling and relationship to strength

In this study we elucidate carbide precipitation at varied cooling rates in Ti–Nb–Mo microalloyed steels during continuous cooling. The study suggests that increasing the cooling rate prevents precipitate formation in the ferrite phase during continuous cooling after finish rolling at 850 °C. At a lower cooling rate of 0.5 °C/s, the microhardness of ferrite grains exhibited maxima because of high volume fraction of fine carbides. A high density of nanoscale carbides with similar precipitation characteristics, including interphase precipitates, was observed at cooling rates of 0.5 and 1 °C/s, but the carbides were marginally larger and the spacing between them was increased with cooling rate. Additionally, carbide precipitation at a high cooling rate was associated with strain-induced precipitation. Through the analysis of selection area electron diffraction patterns and high-resolution transmission electron microscopy, lattice imaging, the fine spherical-shaped carbides of size ~ 6–10 nm were identified as MC-type carbides of the type (Ti,Nb,Mo)C and NbC. - Highlights: • We model three cooling rates which have indicated different precipitation behaviors. • We find two types of precipitates including NbC and (Ti,Nb,Mo)C based on HRTEM study. • Increasing cooling rate will decrease volume fraction and size of the precipitates. • There is no absencemore » of interphase precipitation when the cooling rate increases to 5 °C/s.« less
Authors:
 [1] ;  [1] ; ; ;  [1] ;  [2]
  1. School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)
  2. Center for Structural and Functional Materials Research and Innovation, Department of Metallurgical and Materials Engineering, University of Texas at E1 Paso, 500 W. University Avenue, TX 79968 (United States)
Publication Date:
OSTI Identifier:
22476077
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 102; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CARBIDES; COOLING; DENSITY; ELECTRON DIFFRACTION; LOW ALLOY STEELS; MICROHARDNESS; MOLYBDENUM COMPOUNDS; NANOSTRUCTURES; NIOBIUM COMPOUNDS; PRECIPITATION; RESOLUTION; ROLLING; STRAINS; TITANIUM COMPOUNDS; TRANSMISSION ELECTRON MICROSCOPY