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本文简要报导了15Cr-25Ni-Fe基高温合金在550～650℃长期时效过程中晶界微量σ相析出引起合金脆化效应的研究结果。铁基合金形成σ相的敏感性较大,过去的研究工作得知,晶内呈片层状大量析出的σ相会严重危害合金的强度和塑性。但对晶界微量σ相析出所造成的影响还认识不足。从大量的实验研究结果得出,在15Cr-25Ni-Fe基合金中晶界析出微量σ相(～0.02％)导致合金冲击韧性明显降低,断口从串晶转变为沿晶断裂。合金的脆化程度与反映晶界σ相密集程度的特征量有简单的线性关系。通过相控制合金成分和细化γ晶粒可以清除和降低σ相析出所引起的脆化现象。
This paper briefly reports the results of the study on the embrittlement effect of the alloy caused by the precipitation of σ phase in the grain boundary during the aging of 15Cr-25Ni-Fe superalloy at 550-650 ℃. The formation of σ-phase iron-based alloys is more sensitive. In the past, it has been reported that a large amount of lamellar precipitated σ phase in the crystal would seriously affect the strength and ductility of the alloy. However, the influence of precipitation of trace σ phase on the grain boundary is not fully understood. A large number of experimental results show that the microstructure of 15Cr-25Ni-Fe-based alloy precipitated trace σ phase (~ 0.02%), resulting in significantly lower impact toughness and fracture transition from string to intergranular fracture. There is a simple linear relationship between the degree of embrittlement of the alloy and the characteristic amount reflecting the concentration of the σ phase in the grain boundary. By controlling the alloy composition and refining the γ grains, the embrittlement caused by the precipitation of the σ phase can be removed and reduced.