高速切削锯齿形切屑内绝热剪切带微观特征研究

使用光学显微镜、显微硬度计、X射线衍射、SEM、TEM等方法对高速切削30CrNi3MoV高强度钢锯齿形切屑中第一和第二变形区内形成绝热剪切带和白层进行了观察和研究。结果表明，形成了两种形式的绝热剪切带，即低速下形成的形变带和高速下形成的转变带。转变带内的硬度高于形变带和切屑基体。X射线衍射表明白层内发生了马氏体相变。TEM观察发现，形变带内为经历了大塑性变形的回火马氏体组织。转变带是由尺寸为50～100 nm的等轴晶组成，绝热剪切带形成过程中发生了动态再结晶。

Study on microscopic characteristics of adiabatic shear bands in the serrated chips formed during high speed machining

Adiabatic shear bands and white layers in primary and secondary deformation zones within the serrated chips formed during high speed cutting of 30CrNi3MoV steel were investigated by optical microscope, microhardness tester, XRD, SEM and TEM. Results show that two types of adiabatic shear bands, i.e. deformed shear bands and transformed shear bands, were formed during lower and higher cutting speed respectively. The microhardness in the transformed shear bands is higher than that in deformed bands and matrix of chips. XRD investigation shows that martensitic phase transfor- mation takes place in the white layers. TEM observation reveals the equiaxed grains with diameter of 50- 100 nm in center of transformed shear bands, this means that dynamic recrystallization occur during formation of shear bands.