Abstract: Using conventional heat treatment combined with electrical pulse treatment （abbreviated EPT） ，the M2 high-speed steel was processed and the microstructure was observed using microscope， SEM and EBSD， the bending resistance of the specimen was tested. The results showed that the prior austenite grains （abbreviated PAGs） size of sample pretreated at 1 200 ℃ was about 24 μm， the austenite grain size was significantly refined after EPT， the grain size was refined to 4.8 μm while quenching at 1 140 ℃.The maximum bending strength of the refined M2 high-speed steel reached to 3 799 MPa， which was 39% higher than quenching at 1 180 ℃ of conventional heat treatment（abbreviated CHT）.Compared with the size change of austenite grain of M2 high-speed steel during the CHT ， it can be found that the grain refinement effect produced by EPT was not due to cyclic quenching， but it should be due to the high overheat generated by rapid heating and the influence of non-thermal effect on the nucleation rate.

Key words: M2 High-speed Steel, Grain Refinement, Electropulsing Treatment, Bending Strength.

摘要： 采用传统热处理结合电脉冲处理的方法，对M2高速钢进行了处理，利用金相显微镜、SEM和EBSD观察了显微组织，测试了试样的抗弯性能。结果表明，1 200 ℃预处理试样的奥氏体晶粒尺寸约为24 μm，经过电脉冲处理后，奥氏体晶粒尺寸显著细化，在1 140 ℃淬火时的晶粒尺寸细化到4.8 μm。细化后的M2高速钢抗弯强度最高达到3 799 MPa，比常用热处理1 180 ℃淬火时的抗弯强度提高了39%。与单纯热处理时M2高速钢的奥氏体晶粒尺寸变化相比，可以发现，电脉冲处理产生的晶粒细化效果不是由于循环淬火，而应当是源于快速加热产生的高过热度，以及非热效应对形核率的影响。

关键词: M2高速钢, 晶粒细化, 电脉冲, 抗弯强度