渗碳体粒子尺寸对低碳钢铁素体动态再结晶的影响

EFFECT OF CEMENTITE PARTICLE SIZE ON DYNAMIC RECRYSTALLIZATION OF FERRITE IN A LOW CARBON STEEL

利用单向热压缩实验和OM、SEM、EBSD及TEM技术,研究了低碳钢铁素体晶粒尺寸相似、渗碳体粒子尺寸不同的两种原始组织在700℃、0.01 s^(-1)条件下的组织演变过程,分析了渗碳体粒子尺寸对铁素体动态再结晶的影响.实验结果表明:变形过程中,在尺寸较大的渗碳体粒子附近容易产生大的应变梯度,通过粒子激发形核导致动态再结晶核心的形成.在变形初期,动态再结晶核心主要在尺寸大于1.0μm的渗碳体粒子附近形成;随着应变量的增加,动态再结晶核心也可以在0.5—1.0μm的渗碳体粒子附近形成;而小于0.3μm的渗碳体粒子附近无法形成大的应变梯度,只能钉扎位错和亚晶界,阻碍动态回复和动态再结晶的发展.

The microstructure evolution of ferrite in a low carbon steel during hot uniaxial compression tests at 700 ℃ and 0.01s^-1 was investigated by means of OM, SEM, EBSD and TEM. In order to investigate the effect of cementite particles size on dynamic recrystallization （DRX） of ferrite, two different microstructures consisting of ferrite with similar size and cementite particles with different sizes were adopted by quenching and tempering of a low carbon steel. The results showed that large cementite particles acted as nucleation sites for DRX of ferrite by particle-stimulated nucleation （PSN） mechanism, due to the formation of large orientation gradient near them during hot deformation. In the earlier stage, DRX nuclei were mainly formed near cementite particles with size larger than 1 μm. With increasing strain, the nuclei would also be formed near particles with size between 0.5 to 1 μm. On the contrary, because of much smaller orientation gradient and pinning effect on the dislocation and sub-boundary, the cementite particles with size smaller than 0.3 μm retarded dynamic recovery （DRV） and DRX of ferrite.