钢中贝氏体预相变过程的研究

用扫描俄歇显微探针（ＡＥＳ）分析了６５Ｓｉ２Ｍｎ钢中温转变孕育期内碳原子的成分变化。结果表明，在中温转变孕育期等温时，奥氏体晶界附近及晶内均形成可稳定存在的贫碳区。贝氏体预相变的实质是碳原子向晶界及其他晶体缺陷扩散偏聚而形成贫碳区的过程。中温转变孕育期内形成贫碳区具有热力学及动力学可能性。

STUDY ON DIFPUSION OF CARBONIN PRE-BAINITIC TRASFORMATION

Diffusion and rboibution of carbon in pre-bainitic trandormation beve animportant influence on the forination mechanism of bainitic ferrite in steeis. Up to now,direct compcaition variation of carben has not been studied in detail in this process. So, thepurpose of the thesis is to investigate the diffusion of carbon duruig isothermal holdingduring the incubation peried of bainitic transformation for 65Si2Mn by Scanning AuserMicrcscopo (SAM). The results show that outstanding change of carbon occurs inaustemporing specimens during incubetion poriod when holding at the middle temperaturerather than the dirMiy quenched slwcimens. The pre-bainitic transformation is, in fact , theformation of carbon-depletal region, which exists near the area of grain boundanes andwtthin austenite grains vecause of diffusion and ddering of carben. The carbon depleteddegree increases as the holding time and temperature. The carbon content in carbon-depletedresion is between the mean cartson content of the alloy and the equllibrium carbon contentof ferrite. Therefore, the exfxrimental results support the opinion on the formation ofbainitic ferrite with partial suporsaturation of carbon in carbon-depleted region by inarensitic-tw displacive mechanism. The existence of carbon-depleted region possesses thethermedynamic and kinetic feasibility.