摘要
将Zr-4和成分接近ZIRLO的3#合金样品置于高压釜中,经过360℃,18.6MPa的0.01mol/LLiOH水溶液腐蚀150d后,增重分别达到310mg/dm2和82mg/dm2,3#合金的耐腐蚀性能明显优于Zr-4。用透射电镜、扫描电镜和扫描探针显微镜研究了两种样品经过70d和150d腐蚀后,氧化膜不同深度处的显微组织和晶体结构;研究了氧化膜的断口形貌和氧化膜的表面形貌。结果表明:Zr-4氧化膜中的空位比3#合金氧化膜中的更容易通过扩散凝聚形成孔洞簇和晶界微裂纹,也容易发展成平行于氧化膜/金属界面的裂纹,导致腐蚀转折提早发生,这与Li+和OH-渗入氧化膜后降低氧化锆表面自由能的程度有关。从氧化膜表面晶粒形貌判断,Zr-4样品形成氧化锆后的表面自由能比3#合金样品形成氧化锆后的低,这是合金成分不同引起的一种差异,也可能是Zr-4样品在LiOH水溶液中的耐腐蚀性能比3#样品差的一个重要原因。
Autoclave tests were carried out in the LiOH aqueous solution of 0.01 mol/L at 360℃ and 18.6 MPa for the Zircaloy-4 and 3# zirconium alloys with the composition close to ZIRLO. The weight gains were 310 mg/dm^2 and 82 mg/dm^2, respectively, for the Zircaloy-4 and 3# zirconium alloy specimens after exposure for 150 days. The corrosion resistance of the 3# zirconium alloy is much better than that of Zircaloy-4. The fracture surface morphology and crystal structure of the oxide films were investigated by transmission electron microscopy, scanning electron microscopy and scanning probe microscopy at different oxide film depths for the two specimens after exposure for 70 and 150 days. The results show that the pores clusters and micro-cracks along grain boundaries, which are formed through the diffusion and condensation of vacancies, are easily formed in the oxide films of Zircaloy-4 than that of 3# zirconium alloy due to the reduction of surface free energy of zirconium oxide after the penetration of Li^＋ and OH^- ions into the oxide films. Therefore, the cracks parallel to the interface of oxide/metal are also easily produced in the oxide films of Zircaloy-4 specimens so that the corrosion resistance is degraded. Based on the judgment of the grain morphology on the surface of oxide films after corroded in LiOH aqueous solution, it is concluded that the surface free energy of oxide film for Zircaloy-4 is lower than that for 3# zirconium alloy. This might be one of the important factors for the difference of corrosion behavior between Zircaloy-4 and 3# zirconium alloys during corrosion tests in LiOH aqueous solution.
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2006年第7期1009-1016,共8页
Rare Metal Materials and Engineering
基金
国家自然科学基金资助项目(50171039和50371052)
上海市重点学科建设资助项目(T0101)
关键词
锆合金
腐蚀
氧化膜
显微组织
水化学
zirconium alloys
corrosion
oxide films
microstructure
water chemistry
