论文部分内容阅读
为精确控制热轧780 MPa级Nb-Ti微合金化C-Mn钢中的纳米析出物(Nb,Ti)C,利用热力模拟实验技水,通过透射电镜观察及统计分析,研究形变及冷却速率对纳米析出的影响规律.结果表明,形变可显著地提高析出物形核率,并细化析出物平均直径;析出物数量随冷却速率的增大逐渐减小;既定的实验条件下,冷却速率达到15℃/s可完全抑制析出物在冷却过程中形核;随着冷却速率的增大,析出物的形核区间由奥氏体区形核向铁素体或贝氏区转变,析出物平均直径明显细化;在低冷却速率条件下的变形实验钢中,形变提高组织中的空位浓度,促进析出物空位形核的发生;晶界或亚晶界是过饱和空位的主要陷阱,但空位的扩散活性很高致使低冷却速率条件下晶界或亚晶界附近的空位浓度低于析出物形核的临界形核浓度,从而无法形核,形成晶界附近无析出带;无析出带宽度随冷却速率的增大而减小,这归因于空位扩散活力随冷却速率的增大而降低.
In order to precisely control the nano-precipitates (Nb, Ti) C in hot rolled 780 MPa Nb-Ti microalloyed C-Mn steel, the effects of deformation and cooling rate The results show that deformation can significantly improve the rate of precipitate nucleation and refine the average diameter of precipitates. The amount of precipitates decreases with the increase of cooling rate. Under the given experimental conditions, the cooling rate With the cooling rate increasing, the nucleation interval of the precipitates changed from the nucleation of austenite region to the ferrite or Beyer’s zone, and the precipitates The average diameter is obviously refined. In the deformed steel under the condition of low cooling rate, the deformation increases the vacancy concentration in the structure and promotes the occurrence of vacancy nucleation. The grain boundary or subgrain boundary is the main trap of supersaturated vacancy. The diffusion activity of vacancies is so high that the vacancy concentration near the grain boundaries or the subgrain boundaries at a low cooling rate is lower than the critical nucleation concentration of precipitates nucleation to form nuclei with no precipitation around the grain boundaries. Width increases with cooling rate Reduced due to the diffusion of vacancies with dynamic cooling rate increases.