The corrosion of Zr(Fe, Cr)2 and Zr2Fe secondary phase particles in Zircaloy-4 under 350 °C pressurised water conditions
The corrosion of Zr(Fe, Cr)2 and Zr2Fe secondary phase particles in Zircaloy-4 under 350 °C pressurised water conditions
复制标题
DOI：
10.1016/j.corsci.2017.09.014
复制
发表时间：
2017-11-01
影响因子：
8.3
通讯作者：
Gass, Mhairi
中科院分区：
文献类型：
--
作者：
Annand, Kirsty;Nord, Magnus;Gass, Mhairi
用扫描电子显微镜(STEM)、双电子能量损失谱(DualEELS)和扫描衍射仪研究了Zircaloy-4材料氧化层中第二相粒子(SPPs)的腐蚀和掺杂。本研究的重点是绘制氧化过程中的Zr2Fe和Zr(Fe，Cr)(2)析出物的腐蚀图谱，并描绘其在氧化前沿穿过材料时的形态。结果表明，Zr2FeSPP保持了与预氧化阶段相同的基本形状，并转变为纳米晶均匀的混合氧化物，具有较强的晶体织构，但结构至今未知。然而，Zr(Fe，Cr)(2)Laves相SPP的氧化方式明显更为复杂。当SPP周围的α-Zr开始氧化时，SPP完全被ZrO2包裹，而SPP的大部分最初保持未被氧化。但是，在氧化时，会发生显著的元素偏析，通常会留下富Cr2O3的帽子、纳米晶的Zr、Cr混合氧化体和结晶良好的金属铁脉。这两种形式的SPP在氧化过程中的膨胀程度都不同于Zr，从而导致了ZrO2的开裂。
Using Scanning Transmission Electron Microscopy (STEM) coupled with Dual Electron Energy Loss Spectroscopy (DualEELS) and scanned diffraction, the corrosion and incorporation of Secondary Phase Particles (SPPs) in the oxide layer of Zircaloy-4 material has been investigated. This study focuses on mapping the corrosion of Zr2Fe and Zr(Fe, Cr)(2) precipitates during the oxidation process and depicting their morphology as the oxidation front advances through the material. It has been found that Zr2Fe SPPs retain the same general shape as in their pre oxidation stage, and transform to a nanocrystalline homogeneous mixed oxide, with a strong crystallographic texture, but hitherto unknown structure. The Zr(Fe, Cr)(2) Laves-phase SPPs however, oxidise in a notably more complicated manner. As the alpha-Zr around an SPP begins to oxidise, the SPP is completely encapsulated by the ZrO2 whilst much of the SPP remains initially unoxidised. But, on oxidation, significant elemental segregation takes place, usually leaving a Cr2O3-rich cap, a nanocrystalline Zr,Cr mixed oxide body and veins of well crystallised metallic iron. Both forms of SPP have a different expansion on oxidation compared to the Zr, resulting in cracking of the ZrO2.