超低碳钢等温时效过程中析出物的电镜观察

An SEM study of the precipitates formed during isothermal-aging of an ultra-low carbon steel

采用扫描电子显微镜研究了超低碳钢在650℃经100 s、1 000 s、100 h、300 h等温时效过程的组织变化及铜的析出颗粒,探讨了时效时间与铜原子扩散对富铜析出颗粒的影响.研究结果表明,等温时效后的组织为多边形铁素体晶粒,富铜析出颗粒优先在铁素体晶界处析出,随着时效时间的延长,在铁素体晶粒内部也出现了富铜析出颗粒.计算表明在晶粒内部的铜原子完全可以借助位错和晶界的高扩散率通道,逐渐富集、长大并粗化.

The microstructure and Cu precipitate formed in an uhra-low carbon steel isothermally aged at 650℃ for 100 s, 1 000 s, 100 h, and 300 h were characterized by means of scanning electron microeope. The influence of aging time and copper diffusion on the precipitation of copper-rich precipitates was discussed. The results showed that the microstruetures of the aged steel were composed of polygonal ferrite grains with Cu-rich particle precipitated first at the ferrite grain boundaries, and then, with increasing the aging time, within the feirite grains themselves. Calculations showed that with the copper atoms diffusing along the high diffusivity paths of dislocation and grain boundary, the copper-rich precipitates were able to gradually segregate, grow and coarsen.