低碳微量铌钢形变强化相变的组织演变

利用热模拟压缩变形实验研究了含Nb钢过冷奥氏体形变强化相变的组织演变规律,探讨了微量Nb对形变强化相变的影响,并对转变动力学和晶体取向进行了分析.结果表明,含Nb钢在A3-Ar3之间的形变过程中主要以形变强化相变为主.与低碳钢相比,含Nb钢形变强化相变的孕育期变长,完成相变所需的应变量也相应增加,使得其转变动力学曲线向高应变方向平移.含Nb钢的转变动力学曲线可划分成两个阶段,其中第一阶段固溶Nb阻碍铁素体相变,使孕育期推迟,而第二阶段形变过程中动态析出的Nb(C,N)既为铁素体相变提供了大量的形核位置,又钉扎铁索体晶界,阻碍铁索体晶粒的长大.在这种以形核为主的过程中出现了<111>和<001>两种织构的交替变化.

Microstructure Evolution During Eformation--Enhanced Transformation in

The microstructure evolution during deformation enhanced transformation of supercooled austenite in Nb-microalloyed steel has been investigated by means of hot compression simulation experiment. The effect of Nb on the strain enhanced ferrite transformation has been studied and the transformation kinetics and orientation of Nb-microalloyed steel has also been analysed. The experimental results showed that the deformation-enhanced transformation is a dominated factor at the deformation temperature between A3 and Ar3. The transformation incubation period of Nb-microalloyed steel was prolonged and therefore the higher strain was needed to accomplish the transformation. The transformation kinetics curves moved to high strain parallelly, and can be divided into two stages: at the first stage the solute Nb dragged the ferrite transformation and led to a long incubation period; at the second stage the fine Nb(C, N) particles not only produced many favorable nucleation sites for ferrite transformation, but also inhibited the grain growth of ferrite. The microstructure evolution is a nucleation dominated process, in which the interchange between <001>nd <111>exture appeared.