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本文对40MnB、40Cr两种中碳钢低温回火马氏体的力学性能及疲劳裂纹扩展进行了对比研究。揭示了这两种钢在相近的高强度状态疲劳裂纹扩展行为及沿晶、穿晶断裂机制对裂纹扩展速度的影响。结果表明,微量合金元素硼改变了裂纹扩展途径和扩展方式,从而降低了疲劳裂纹扩展速率。40MnB钢较高的断裂韧性K_(IC)和断口显示的疲劳裂纹扩展机制,与硼所引起的组织精细结构的变化有密切关系。
In this paper, 40Mn, 40Cr two kinds of low carbon tempered martensite mechanical properties and fatigue crack growth were compared. The effects of fatigue crack propagation and crack propagation along the intergranular and transgranular fracture mechanisms on the strength of the two steels were revealed. The results show that the microalloy elemental boron changes the way of crack propagation and the mode of expansion, thus reducing the fatigue crack growth rate. The higher fracture toughness K IC and fracture fatigue crack growth mechanism of 40MnB steel are closely related to the change of the fine structure of the microstructure caused by boron.