锆-4合金氧化膜中的晶粒形貌观察

The Grains Morphology of Oxide Films for Zircaloy-4

用扫描探针显微镜(SPM)研究了Zr-4合金在高压釜中经360℃高温水腐蚀后氧化膜中的显微组织和晶粒形貌。从氧化膜表面上观察到的晶粒在100nm～400nm之间,比从截面上观察到的大,说明氧化膜的晶粒在腐蚀过程中仍在不断长大。从离子轰击蚀刻后的氧化膜截面上,可以区分出由大角度晶界构成的柱状晶,以及在柱状晶中由小角度晶界构成的等轴晶。在三晶交界处,常常有明显的“凹陷”,这应是空位扩散凝聚后形成的空洞,尺度在几纳米至几十纳米间。在氧化膜的截面上,除了可观察到裂纹和空洞等缺陷外,在氧化膜/金属交界处,有时还可观察到片层状的氢化锆和显示不出晶界的非晶ZrO2。

The microstructure and morphology of oxide film for Zircaloy-4 alloy in autoclave at 360degreesC and 18.6MPa have been investigated by means of scanning probe microscopy (SPM). The diameter of grains observed on the surface of oxide films is 100mn similar to 400nm, which is larger than that observed on the section of oxide films. This means that the grain still grow during the process of corrosion testing. Some column grain with large angle grain boundaries can; be observed on the section surface etched by ion-bombardment, and some small equal-axis grains with small angle grain boundaries exist in the column grains. Some depressed areas in the size of nanometer to decadal nanometer can be found at the junctures of three or more grains, which should be the pores caused by the diffusion and condensation of vacancies. Besides, some flaky zirconium hydrides and amorphous ZrO2 without grain boundaries can be occasionally observed at the metal/oxide interface.