中文摘要：

对热作模具钢进行了脉冲电流处理，研究了脉冲电流处理阶段、脉冲电流持续时间和脉冲电流密度对热作模具钢热疲劳裂纹形貌和裂纹扩展速率的影响，并分析了热疲劳裂纹萌生和扩展的规律，探讨了其作用机理。结果表明，对热作模具钢进行脉冲电流处理可以提高模具钢的抗热疲劳性能，且在热疲劳循环过程中而不是在初始回火态下进行脉冲电流处理可以获得最佳的抗热疲劳性能；脉冲电流持续时间的延长可以有效缩短热疲劳过程中的最大裂纹长度和减少次生裂纹数量，表面龟裂现象有所减缓，还可以降低模具钢试样的热疲劳裂纹扩展速率；脉冲电流密度的增加不仅可以延长疲劳裂纹萌生的时间，还可以降低模具钢试样的热疲劳裂纹扩展速率，从而提高模具钢热疲劳循环服役寿命；经过脉冲电流处理后的模具钢在细晶强化、位错强化和弥散强化的共同作用下，热疲劳性能得到提升。

英文摘要：

Pulse current treatment was carried out on hot work die steel. Effects of pulse current treatment period, pulse duration and pulse current density on thermal fatigue crack morphology and crack growth rate of the hot die steel were investigated, the law of thermal fatigue crack initiation and propagation was analyzed, and its mechanism was discussed. The results show that thermal fatigue resistance of the hot work die steel can be improved by pulse current treatment, the optimal thermal fatigue resistance can be obtained by pulse current treatment during the thermal fatigue cycle rather than in the initial stage ; Prolonging the duration of pulse current can effectively shorten the maximum crack length, reduce the number of secondary cracks during thermal fatigue, slow down the surface cracking phenomenon, and reduce thermal fatigue crack growth rate ; The increase of pulse current density not only can prolong the time of fatigue crack initiation, but also can reduce the thermal fatigue crack growth rate of the die steel specimens, so as to improve the service life of thermal fatigue cycle of the die steel. Under the combined action of fine grain strengthening, dislocation strengthening and dispersion strengthening, the thermal fatigue property of the die steel after pulse current treatment is improved.