为了揭示高速切削过程中切屑形成以及刀具-切屑界面摩擦机理,对剪切区内剪切带及白层进行了微观观察和分析.利用光学显微镜,SEM,电子探针,TEM和X射线衍射等方法对高速切削淬硬钢锯齿状切屑剪切变形区内变质层的微细组织进行了观察,对变质层的微结构本质及其形成机理进行了分析.研究表明：在锯齿状切屑锯齿之间的第一变形区存在绝热剪切带,由切屑基体到剪切带中心依次出现马氏体板条、沿剪切方向拉长并被位错分割的板条和等轴晶粒等不同的微结构特征;在切屑底部的第二变形区存在白层,其微结构显示了非晶组织特征.剪切带形成过程中没有相变发生,其形成是基于一种旋转式动态再结晶机制,白层的形成过程中发生了非晶转变和马氏体相变,形成机理属于相变机制.
To reveal the mechanism of chip formation and tool-chip interface friction during high speed machi- ning, the microstrueture observation by optical microscope, SEM, electron probe and TEM, and the analysis of shear band and white layer in shear deformation were carried out. The investigation shows that there are adia- batic shear bands in primary shear zones between the saw teeth. The different microstructures, such as martens- ite lath, elongated martensite laths divided by dislocations and equiaxed grains, appear in turn from the chip matrix to the center of shear band. There are white layers, which have amorphous microstructure, in second shear zones on the bottom of chips. No phase change occurs during the formation of shear band, but its forma- tion mechanism is based on a rotary dynamic recrystallization, while the amorphous and martensite transforma- tion occur during the formation of white layer, its formation is based on phase transition mechanism.
参考文献
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