添加Al、Cu对40CrNi3MoV钢组织和力学性能的影响

利用OM、SEM、TEM以及力学性能测试等表征手段研究了添加Al、Cu的40CrNi3MoV钢在900 ℃油冷淬火及450~650 ℃回火后的显微组织和力学性能的变化规律。结果表明,试验钢经淬火+回火后的显微组织主要为回火索氏体,同时析出了纳米级NiAl-Cu析出相,最佳回火温度区间为500~550 ℃。由于基体中析出纳米尺度B2结构的NiAl析出相,对添加Al的试验钢中微裂纹的扩展有较强的阻碍作用, 500~550 ℃回火时抗拉强度最高增幅达200 MPa;进一步添加Cu后,富Cu相和位错的相互作用使得试验钢的屈服强度提高了150 MPa。500 ℃回火时抗拉强度为1706 MPa,屈服强度为1505 MPa,试验钢的拉伸和冲击断口呈现出典型的解理断裂特征,有明显的撕裂棱。

Effects of Al and Cu additions on microstructure and mechanical properties of 40CrNi3 MoV steel

Change of microstructure and mechanical properties of 40CrNi3MoV steel with Al and Cu additions after oil quenched at 900 ℃ and then tempering at 450-650 ℃ was studied by OM, SEM, TEM and mechanical properties test. The results show that the microstructure of the tested steel after quenching and tempering is mainly tempered sorbite with nano-scale NiAl-Cu precipitates and the range of optimal tempering temperature is 500-550 ℃. The precipitation of NiAl precipitates with nano-scale B2 structure in the matrix has a strong hindering effect on the propagation of micro-cracks in the tested steel with Al addition, and the resulted maximum increase of tensile strength of the steel is 200 MPa. While after further addition of Cu, the yield strength increment of the tested steel is 150 MPa due to the interaction of the Cu-rich phase and dislocations. In such state, the tested steel owns tensile strength and yield strength of 1706 MPa and 1505 MPa respectively, and its tensile and impact fractures show typical cleavage fracture characteristics with obvious tearing edges.