采用XRD物相分析、金相组织观察及TEM精细组织分析研究了奥氏体组织结构状态对Fe-0.88C-1.35Si-1.03Cr-0.43Mn钢中温等温相变鼻温和孕育期的影响，以及不同温度奥氏体化后240℃等温20 min试样的组织结构特征。试验发现，随着奥氏体化温度的升高，中温等温开始转变的鼻温移向更低温度并且相变孕育期缩短；不同温度奥氏体化后同为240℃等温20 min处理，虽然均形成由贝氏体铁素体亚条平行排列构成的束状贝氏体组织，但贝氏体组织的精细结构状态不同，突出的差别在于对应低温奥氏体化贝氏体亚条端部边界具有凸起结构，而对应高温奥氏体化贝氏体亚条端部边界较为平齐且呈现楔形结构。不能简单地以马氏体切变机制认识试验钢中贝氏体组织的形成。
The influence of austenitization temperature on the incubation period and the bainitic phase transformation be-haviour in high-carbon silicon steel has been investigated using X-ray diffraction (XRD), optical microscopy and transmis-sion electron microscopy (TEM). The microstructure characteristics of the isothermal transformation (240 ℃, 20 min) products were also studied. It was found that the nose temperature of bainite transformation and incubation period de-creased with the increasing austenitizing temperature. After isothermal heat treatment at 240 ℃ for 20 min, all samples were austenitized at different temperatures produced a bainitic structure, which consisted of packets of parallel ferrite laths. However, notable differences in sub-structure were found among these samples. When it was austenitized at lower temperature, the major difference lied in the edge boundary morphology. Bainitic laths formed in low-temperature austen-itizing conditions had sharp saw-tooth edge boundaries, whereas bainite transformed from high-temperature austenitizing conditions had smooth wedge boundaries. The observed bainite packets did not possess the twin substructure of quenched martensite and its corresponding strain accommodation microstructure. The formation of packet bainitic structures investi-gated in this study cannot be simply explained by martensitic displacive transformation mechanism. Further research is re-quired to clarify the baintic transformation mechanism.
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