热变形对Fe-0.2C-2Mn合金γ→α转变动力学的影响及理论探讨  

EFFECT OF HOT DEFORMATION ON KINETICS OF γ→α TRANSFORMATION IN A Fe-0.2C-2Mn ALLOY AND RELATED THEORETICAL ANALYSES

作　　者：夏苑[1] 杨志刚[1] 李昭东[1] 张玉朵[1] 张弛[1] 

机构地区：[1]清华大学材料科学与工程系先进材料教育部重点实验室,北京100084

出　　处：《金属学报》2012年第3期271-276,共6页Acta Metallurgica Sinica

基　　金：国家自然科学基金资助项目51071089~~

摘　　要：通过热处理实验和理论计算研究了热变形条件下Fe-0.2C-2Mn合金先共析铁素体转变动力学.金相观察表明,热变形细化铁索体组织,并使铁素体形貌趋于等轴状.在PLE/NPLE理论基础上,运用Pillbox模型和抛物线长大模型计算了变形前后铁素体的晶界形核率和长大系数,结果表明,过冷奥氏体变形促进NPLE模式下铁素体形核的主要原因是奥氏体晶界面积增加和元素扩散加快,而PLE模式下则是相变驱动力增大占主导.最后对比分析了热变形对形核和长大的影响程度,阐明了热变形细化不同温度区间转变的铁素体组织的机制.γ→αtransformation 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.

关 键 词：热变形 晶粒细化 先共析铁素体 动力学 

分 类 号：TG111.3[金属学及工艺—物理冶金]