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Zr-4合金大晶粒样品在360℃和18.6 MPa的0.01 mol/L Li OH水溶液中经过70和160 d腐蚀后,采用EBSD,SEM和HRTEM等方法,研究了氧化膜的显微组织和晶体结构,以及氧化膜的厚度与金属晶粒表面取向的关系.结果表明,样品经过160 d腐蚀后,金属晶粒表面取向在靠近(0001)附近时氧化膜相对较厚,氧化膜的生长显示出明显的各向异性特征,但是在腐蚀70 d后这种特征还不明显.从腐蚀70 d后的样品中选取了表面取向接近(0001),(1010)和(1120)的金属晶粒,研究了它们表面上氧化膜/金属界面处的显微组织,不同取向金属晶粒表面上形成氧化膜的显微组织存在一定差别,在取向接近(0001)的晶粒表面生成的氧化膜中的m-Zr O2柱状晶晶粒之间的取向差比较大,氧化膜显微组织和晶体结构非常复杂,除主要的m-Zr O2外,还存在c-Zr O2,t-Zr O2以及亚氧化物Zr3O.氧化膜显微组织在腐蚀过程中不断发生演化,这会影响氧离子的扩散,进而影响氧化膜的生长,这种显微组织的演化过程还会受到氧化膜在不同取向晶粒表面上形成初期显微组织差别以及腐蚀时水化学条件的影响,这是Zr-4在Li OH水溶液中腐蚀时会出现氧化膜生长各向异性特征的主要原因.
Large grain samples of Zr-4 alloy were eroded for 70 and 160 d in 0.01 mol / L LiOH aqueous solution at 360 ℃ and 18.6 MPa. The microstructure and the crystal structure of the oxide film were studied by EBSD, SEM and HRTEM. Structure and the relationship between the thickness of the oxide film and the surface orientation of the metal grain were investigated.The results show that the oxide film is relatively thick when the surface of the metal grain is oriented near (0001) after the sample is etched for 160 days and the growth of the oxide film shows Obvious anisotropy, but this characteristic is not obvious after 70 days of corrosion.The metal grains with the surface orientation close to (0001), (1010) and (1120) were selected from the samples after 70 days of corrosion, The microstructures at the oxide film / metal interface on the surface of the oxide films are different from each other. The difference between the microstructures of the oxide films formed on the surfaces of the different orientation metal grains is that the m -Zr O2 columnar crystal grain orientation difference is relatively large, the oxide film microstructure and crystal structure is very complex, in addition to the main m-ZrO2, there are c-ZrO2, t-ZrO2 and sub-oxide Zr3O. The oxide film microstructure evolves continuously during the etching process, which affects oxygen The diffusion of the daughter and then the growth of the oxide film. The evolution of this kind of microstructure is also influenced by the initial microstructure difference of the oxide film formed on the surface of the different orientation grains and the chemical conditions of water during corrosion. This is the result of Zr- 4 in the aqueous solution of LiOH corrosion occurs when the oxide film growth anisotropy characteristics of the main reasons.