中文摘要：

使用光学显微镜、扫描电子显微镜（SEM）和透射电子显微镜（TEM）对高速切削淬硬30CrNi3MoV高强度钢形成的锯齿状切屑主剪切区内材料微观特征进行了观察,并对绝热剪切失稳的微观机理进行了分析.微观观察和分析结果表明,绝热剪切带中心由平均直径0.4～0.6μm的细小等轴晶粒组成,过渡区内为碎化并沿剪切方向拉长的马氏体板条组织.锯齿状切屑的形成应归因于主剪切区材料绝热剪切失稳的发生,在此过程中,动态回复和再结晶成为微结构演化的主要冶金过程,绝热温升起到了关键作用.等轴晶组织的形成机制为旋转式动态再结晶.

英文摘要：

The metallurgical characters of the primary shear zones in the serrated chips produced during high-speed machining 30CrNi3MoV quenched high strength steel were observed using optical microscope,scanning electron microscopy （SEM） and transmission electron microscopy （TEM）,and the microcosmic mechanism of adiabatic shear instability was analyzed. The observations and analyses show that the fine equiaxed grains appear with size of about 0.4-0.6 μm in the center of adiabatic shear bands,and the transitional region is characterized by the broken and elongated martensite laths in shear direction. The formation of serrated chip should be due to adiabatic shear instability occurring in the primary shear zones,during which the microstructure development of dynamic recovery and recrystallization is the dominant metallurgical process and adiabatic temperature rise plays a critical role. The fine equiaxed grains are created by rotational dynamic recrystallization.