镍对奥贝球铁中上贝氏体第一阶段转变动力学的影响

Influence of Nickel on Kinetics of Upper Bainitic Transformation of the First Stage of Austempered Ductile Iron (ADI)

本文定量地讨论了镍含量与奥贝球铁中上贝氏体第一阶段转变时间的关系,研究了镍对上贝体转变孕育期、奥氏体化开始温度和残余奥氏体中含碳量的影响;揭示了镍及其偏析在上贝氏体第一阶段转变中的作用。结果表明:随着镍含量的增加,上贝氏体第一阶段转变速度、奥氏体化开始温度和残余奥氏体中的含碳量降低。当镍含量超过2％时,第一阶段转变速度显著减慢。镍的偏析使得奥贝球铁基体中上贝氏体转变速度不一致,造成组织不均匀;镍与锰的综合加入可以改善由于单独加镍对奥贝组织的不利影响。

In this paper, we have quantitatively discussed the relation between the nickel content and upper bainitic transformation time of the first stage of ADI. studied the influence of nickel on the inoculation time of upper bainitic transformation, start austenizing temperature of ductile iron. retained austenite content and it's carbon content, revealed the function of nickel and it's segregation in the upper bainitic transformation of the first stage. The results show that. with the increase of nickel content. the transformation rate of uppper bainite of the first stage, the start austenizing temperature of ductile iron and the carbon content of retained austenite decrease. When the nickel content is above 2%. the upper bainitic transformation rate decrease abviously. The segregation of nickel lead to the difference of upper bainitic transformation rates in the matrix of ADI. The combined addition of nickel and manganese can improve the inhomogeneity of the microstructure of ADI. which was caused by the single addition of nickel.