Metallurgical and Materials Transactions A

, Volume 29, Issue 5, pp 1383–1394 | Cite as

Transformation during the isothermal deformation of low-carbon Nb-B steels

  • D. Q. Bai
  • S. Yue
  • J. J. Jonas
  • T. M. Maccagno
Article
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Abstract

The transformation behavior during isothermal deformation of four steels containing different microalloying additions was investigated by means of the “strain-rate change” technique. The flow curves obtained at temperatures ranging from 620 °C to 850 °C, and the associated microstructures, indicate that the transformation in the Mo-Nb-B and Mo-B steels is of the austenite-to-bainite type. Here, dramatic increases in flow stress are observed at lower temperatures. By contrast, the transformation in the Nb-15B and Nb-64B steels is basically of the austenite-to-ferrite type; in these two grades, the flow stress increases observed are attributable to strengthening by NbC precipitation. Large intergranular and intragranular Fe23(C,B)6 particles were found in the Nb-64B steel samples deformed to ɛ=0.1 after holding for 60 seconds at 800°C. These large precipitates are considered to be responsible for accelerating the transformation in the Nb-64B steel by reducing the concentration of boron atoms available for boundary segregation and by acting as nucleation sites for the formation of polygonal ferrite. The flow curves of the Mo-Nb-B steel exhibit distinct serrations, indicating that a displacive mechanism is involved in the γ-to-B transformation.

Keywords

Ferrite Austenite Material Transaction Bainite Deformation Temperature 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 1998

Authors and Affiliations

  • D. Q. Bai
    • 1
  • S. Yue
    • 1
  • J. J. Jonas
    • 1
  • T. M. Maccagno
    • 2
  1. 1.the Department of Metallurgical EngineeringMcGill UniversityCanada
  2. 2.the Department of Chemical and Materials EngineeringUniversity of AlbertaEdmontonCanada

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