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研究了00Cr25Ni7Mo4N超级双相不锈钢在600～1 000℃不同温度时效以及920℃和830℃等温时效过程中的χ相析出规律,利用扫描电镜的背散射电子探测器观察了χ相的析出数量和分布,采用透射电镜和X射线能谱仪分析了χ相的结构和成分。结果表明,χ相的析出温度范围在750～920℃之间,其峰值温度约为830℃。相比σ相,χ相析出数量较少,主要分布在α/γ相界和α/α晶界。从等温时效过程看,00Cr25Ni7Mo4N钢中χ相的析出经历了孕育、快速析出、达到饱和以及逐渐转变为σ相的系列过程,表明χ相是一种亚稳相,随着时效时间的延长,χ相会转变为σ相。

Precipitation behavior of chi（χ） phase in the super duplex stainless steel 00Cr25Ni7Mo4N was investigated during an aging process at different temperature from 600 ℃ to 1 000 ℃ and during an isothermal aging process at 920 ℃ and 830 ℃.The backscatter electron detector of SEM was used to examine the amount and distribution of Chi（χ） precipitate.TEM and EDS were used to examine the structure and chemical composition of χ-phase.The results show that the precipitation temperature region of χ-phase is from 750 ℃ to 920 ℃,and the peak temperature is about 830 ℃.Comparing with σ-phase precipitation,the amount of χ-phase precipitates is few.The α/γ interfaces and the α/α grain boundaries are the main sites of χ-phase precipitates.During an isothermal aging process,it is found that the precipitation of χ-phase in the 00Cr25Ni7Mo4N steel includes four stages of initiation,rapid precipitation,saturation and transformation into σ-phase.Therefore,the χ-phase is a meta-stable phase,which will gradually transform into the σ-phase after a prolonged aging.