摘要
在不同水化学条件下的高压釜中研究了Zr-4合金在LiOH水溶液中的耐腐蚀性能.结果表明,不同的腐蚀介质对氧化膜内的压应力和t-ZrO2的含量的影响有很大不同;Zr-4合金在LiOH或KOH水溶液中腐蚀时,Li+比K+进入氧化膜深而且浓度高;在LiOH水溶液中腐蚀时,氧化膜中OH-的浓度比在KOH水溶液中高.锆合金在LiOH水溶液中腐蚀时,氧化膜的生长主要是通过OH-从合金的表面向内扩散,与锆反应生成氧化锆和原子氢.Li+半径较小,容易进入氧化膜,因此较多的OH-进入氧化膜的深处,并与t-ZrO2中的氧空位反应,使t-ZrO2向m-ZrO2转变.这导致氧化膜出现裂纹,使氧化膜中的压应力松弛,降低氧化膜的保护能力,提高了锆合金的腐蚀速率.
Autoclave experiments in different water chemistry were conducted to clarify the degradation behavior of zircaloy-4 corroded in LiOH aqueous solution. It was found that the compressive stress and the tetragonal zirconia (t-ZrO2) contents in oxide films formed in different media were different; when specimens were exposed in LiOH and KOH solutions with same concentration, the penetration depth was shallower and the intensity of K+ was weaker than that of Li+, and the penetration depth of OH- corroded in KOH solution was also shallower than that corroded in LiOH solution. Based on the results, it is suggested that the growth of oxide films is a process of OH- diffusing from outside of oxide into metal/oxide interface and reacting with zirconium to form ZrO2 and hydrogen. It is easy for Li+ to diffuse into oxide film because of small radius when specimen is exposed in LiOH aqueous solution, so more OH- would diffuse into oxide film deeply. The reaction between adequate OH- and oxygen vacancies in the t-ZrO2 would promote the transformation from t-ZrO2 to monoclinic zirconia (m-ZrO2). The transformation would bring some cracks in the oxide, which relaxed the compressive stress in the oxide, degraded the protective ability of oxide films and caused an enhancement of corrosion rate of zircaloy-4 alloy.
出处
《材料研究学报》
EI
CAS
CSCD
北大核心
2004年第3期225-231,共7页
Chinese Journal of Materials Research
基金
国家自然科学基金50171039和50301009资助项目
