Paper Title:
Effect of Cold Deformation on Thermal Stability of Bainite in Nb-Bearing Microalloyed Steels
  Abstract

Bainite in microalloyed steel possesses excellent synthetic mechanical properties. However, it will probably evolve towards equilibrium microstructure when it is subjected to thermal disturbance. In addition, bainite frequently undergoes more or less deformation during manufacture of steel structure. In the present investigation, cold deformation test, isothermal heat treatment, hardness measurement, optical microscopy and transmission electron microscopy were employed to detect evolution behavior of bainite isothermally held below A1 temperature. It was found that hardness of samples drops in generally during the isothermal heat treatment. Meanwhile, bainite evolves gradually into polygonal ferrite. Cold deformation enhances the initial hardness of samples while it largely accelerates softening and evolution of microstructure towards equilibrium one during heating. Almost same effects are produced by tensile strain and compressive strain. Higher solubility product of carbon and niobium results in higher thermal stability of bainite. Cold deformation cause dislocations in bainitic laths to distribute heterogeneously and most dislocations pile up along boundaries. During isothermal holding, dislocations redistribute further followed by extending of low dislocation density areas across lath boundaries. Finally, polygonal ferrite nucleates in those areas and grows gradually.

  Info
Periodical
Materials Science Forum (Volumes 638-642)
Main Theme
Edited by
T. Chandra, N. Wanderka, W. Reimers , M. Ionescu
Pages
3093-3098
DOI
10.4028/www.scientific.net/MSF.638-642.3093
Citation
S. W. Yang, H.Q. Lv, R. Zhang, Y. He, X. L. He, "Effect of Cold Deformation on Thermal Stability of Bainite in Nb-Bearing Microalloyed Steels", Materials Science Forum, Vols. 638-642, pp. 3093-3098, 2010
Online since
January 2010
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