Zr-4合金在300 ℃去离子水中腐蚀初期氧化膜的研究

Investigation of Oxide Layers Formed Earlier on Zircaloy-4 Specimens Corroded at 300 ℃ in Deionized Water

摘要:

将Zr-4板材制成Φ3 mm透射电镜薄试样，放入高压釜在300 ℃/8 MPa去离子水中短时腐蚀，用光学显微镜、扫描探针显微镜和电子显微镜研究了氧化膜形成初期的晶体结构、与基体晶粒取向间的关系、氧化锆晶体中的缺陷和应变分布。结果表明：光学显微镜下不同取向的金属晶粒表面上氧化膜的厚度不同，呈现出不同的颜色；氧化膜主要由单斜结构的柱状晶组成，还有少量的四方和立方氧化锆，同时还观察到一种a=0.88 nm的BCC结构氧化锆；不同晶体结构的初生氧化锆与α-Zr基体之间存在一种半共格的取向关系：(10-11)α-Zr//(020)m-ZrO2//(002)t-ZrO2//(020)c-ZrO2，某些晶体方向受到了3%-7%压缩；氧化锆晶体中存在大量位错，并存在不均匀的拉压应变，大小在-4.8%至3.5%之间。

Abstract:

Thin specimens in Φ3 mm for transmission electron microscopy observation were prepared using Zircaloy-4 plate. Corrosion tests of these thin specimens were conducted in the autoclave at 300 ℃/8 MPa in deionized water for short time exposure. The oxide layers formed earlier on Zircaloy-4 specimens have been investigated using optical microscopy, scanning probe microscopy and electron microscopy. The results show that the different thickness of oxide layers formed on metal grains with different orietations was in different colours. The oxide layers were mainly composed of columnar grains with m-ZrO2, but a small amount of t-ZrO2 and c-ZrO2 could be also detected. In addition, a kind of zirconia having BCC structure with a=0.88 nm was observed. Semi-coherent relationships between α-Zr matrix and the different crystal structure of zirconia with certain orietation relationship were observed：(10-11)α-Zr//(020)m-ZrO2//(002)t-ZrO2//(020)c-ZrO2. Therefore compressive deformation of 3%-7% in different directions for different crystal structure of zirconia was produced. A lot of dislocations were observed in oxide crystals and the strain in the area around the dislocations was about -4.8% to 3.5% obtained by geometric phase analysis.