本文就铁素体—奥氏体型双相不锈钢00Cr18Ni5Mo3Si2组织稳定性及其对脆性的影响进行了探讨。980℃固溶处理及在450—900℃温度区间时效后产生α→γ′+X(σ)及α→α′+脱溶产物两种类型的组织转变。在450—750℃时效沿晶界发现有一种片状的Fe_3Cr_3Mo_2Si_2金属间相,在铁素体晶内有一种Fe_(2.4)Cr_(1.3)=MoSi拓扑密排相(R相),而在750—900℃时效发现x相只是一个能转变为σ相的亚稳相。本文就α-铁素体等温转变动力学曲线进行了研究。前人研究结果认为本钢脆性是由σ相造成的,本文研究结果发现在550—650℃及800—900℃不同温度区间脆性断裂特征不同,在550—650℃区间沿晶脆性断裂主要是由于沿晶规则排列的片状Fe_3Cr_3Mo_2Si_2金属间相的析出造成的,而在800—900℃区间的准解理断裂则与α相分解为块状的σ相、x相有关。
The influence of the microstructural stability on the embrittlement in ferriticaustenitic stainless steel, 00Crl8Ni5Mo3Si2, was investigated. After solution treated at 980℃ and subsequently aged between 450—900℃, the steel has undergone two types of transformations, namely α→γ'+χ(σ) and α→α'+precipitates of intermetallic phases. During aging in temperature range of 450—750℃, the lamellar intermetallic phases Fe_3Cr_3Mo_2Si_2 precipitates preferentially along grain boundaries and a topological close packed phase Fe_(2.4)Cr_(1.3)MoSi (R phase) appears in the ferrite grains, while in 750—900℃ the χ phase is merely a metastable one which changes easily to σ phase. A study was also made of the kinetic curve of isothermal decompcsition of α-ferrite. The results indicated that the fracture feature of the steel between 550—650℃ is quite different from that between 800—900℃. In the range of 550—650℃, the intergranular brittle fracture is caused substantially by the precipitation of the lamellari ntermetallic phase Fe_3Cr_3Mo_2Si_2 arranged regularly along grain boundaries, but in 800—900℃, thequasicleavage fracture is connected with the lumpy precipitates of σ and χ phases.
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