EFFECT OF HOT DEFORMATION ON KINETICS OF γ→α TRANSFORMATION IN A Fe-0.2C-2Mn ALLOY AND RELATED THEORETICAL ANALYSES
XIA Yuan, YANG Zhigang, LI Zhaodong, ZHANG Yuduo, ZHANG Chi
Key Laboratory of Advanced Materials of Ministry of Education, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084
Cite this article:
XIA Yuan YANG Zhigang LI Zhaodong ZHANG Yuduo ZHANG Chi. EFFECT OF HOT DEFORMATION ON KINETICS OF γ→α TRANSFORMATION IN A Fe-0.2C-2Mn ALLOY AND RELATED THEORETICAL ANALYSES. Acta Metall Sin, 2012, 48(3): 271-276.
Abstractγ→α transformation is one of the most common and important reactions in steels. Lots of previous experimental researches have already evidenced that hot deformation could refine ferrite grains and remarkably improve strength and toughness of low carbon alloy steels, but relevant theoretical researches, especially quantitative descriptions still need deepening. This work, taking a Fe-0.2C-2Mn alloy as research object, investigated the effect of hot deformation on austenite→pro-eutectoid ferrite transformation by means of both thermo-mechanical experiments and theoretical analyses, in an attempt to provide theoretical basis for further grain refinement in low carbon alloy steels. OM observations showed that finer ferrite grains formed with the increase of strain and decrease of deformation temperature, and hot deformation altered the morphology of pro-eutectoid ferrite; Based on Pillbox model and parabolic growth model, grain boundary nucleation rate and parabolic growth constant were calculated respectively under hot deformation condition, both of which were demonstrated to be accelerated by deformation. Under NPLE mode, ferrite nucleation was enhanced by deformation mainly due to the increase of diffusivity and number of nucleation sites, whereas contribution of stored deformation energy to driving force played a key role under PLE mode. A comparison was made between the strengthening effect of deformation on ferrite nucleation and growth, showing that nucleation was accelerated more significantly at most temperature ranges. Thus the grain refinement mechanism of hot deformation was quantitatively explained.
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