铁硅钇合金的高温氧化行为

High-temperature Oxidation Behavior of Fe-Si-Y Alloys

通过光学显微镜、X射线衍射、扫描电镜和热重分析等研究了添加钇对Fe-Si合金在900℃和1000℃、0.1 MPa纯氧气中高温氧化行为的影响。结果表明,随着元素钇含量的增加,Fe-3Si-0.5Y和Fe-3Si-5.0Y合金的晶粒尺寸较Fe-3Si-0Y合金降低约80%和94%,同时,根据X射线分析结果,合金表面氧化膜的晶粒尺寸随着合金晶粒尺寸的降低明显减小。晶粒细化使合金及其氧化膜中的晶界数量增加,并进一步地促进了合金元素和氧在其中的扩散以及SiO2和Y2O3的形成。然而,含钇合金在900℃和1000℃氧化时均未生成单一连续的SiO2或Y2O3氧化层,但晶粒细化后硅和钇氧化物的快速形成及部分地横向连接对元素的扩散仍起到了比较有效的抑制作用,含钇合金的氧化抗力因此得到了提高。讨论了添加元素钇导致的合金晶粒细化对Fe-Si合金氧化行为的影响机制。

By means of optical microscope（ OM）,X-ray Diffraction（ XRD）,scan electron microscope（ SEM） and thermogravimetric analysis（ TGA）,influence of yttrium on oxidation behavior of Fe-Si alloys has been investigated at 900 ℃and 1000 ℃ in 0. 1 MPa flowing pure O2. Results show that as yttrium content in the alloy increases,the grain size of Fe-3Si-0. 5Y and Fe-3Si-5. 0Y alloys is respectively decreased by 80% and 94% compared to that of Fe-3Si-0Y alloy. Additionally,according to the XRD analysis,the grain size of the oxide scales formed on alloys with finer grain size is also decreased. The grain refinement increases the grain boundaries in the alloys and oxide scales,and further enhances the diffusion rate of the alloying elements and oxygen through them. Consequently,the formation of SiO2and Y2O3on Fe-Si-Y alloys has been promoted.However,a single continuous SiO2or Y2O3scale still does not form on yttrium-containing alloys when being oxidized at 900℃ and 1000 ℃,but the rapid formation and partial lateral connection of SiO2and Y2O3due to the grain refinement can restrain the element diffusion in the alloys to some extents,and thus the oxidation resistance of the yttrium-containing alloys is improved. The influencing mechanism of the grain refinement resulting from the addition of yttrium on high-temperature oxidation behavior of Fe-Si alloys is also discussed.