Sn和Nb对锆合金在低真空环境下初期氧化行为的影响

Effect of Sn and Nb Elements on Initial Oxidation Behavior of Zirconium Alloys in Low Vacuum Environment

锆合金是核反应堆中用作核燃料包壳的重要结构材料,研究其在低真空环境下的初期氧化行为有助于认识锆合金的氧化机制。本工作将Zr-0.75Sn-0.35Fe-0.15Cr、Zr-0.75Sn-0.35Fe-0.15Cr-0.15Nb和Zr-1.5Sn-0.35Fe-0.15Cr(质量分数,%,下同)3种合金制成大晶粒样品,再用电解双喷制成透射电子显微镜(TEM)薄样品,并通过大晶粒TEM薄样品在真空度为3 Pa的真空管式炉中进行280和290℃的氧化实验来研究Sn和Nb对锆合金初期氧化行为的影响。结果表明:添加Nb或提高Sn含量均促进Zr-0.75Sn-0.35Fe-0.15Cr合金在低真空条件下280和290℃氧化初期ZrO2晶粒的形核和长大。低真空条件下280℃/30 min氧化时,添加Nb会促进ZrO2晶粒增大,而提高Sn含量使ZrO2晶粒由球状变为短棒状。随着氧化温度升高(290℃/30 min),Zr-0.75Sn-0.35Fe-0.15Cr和Zr-1.5Sn-0.35Fe-0.15Cr合金表面ZrO2晶粒出现长大现象,而Zr-0.75Sn-0.35Fe-0.15Cr-0.15Nb合金表面ZrO2晶粒形核速率较快。

Zirconium alloys are important structural materials used as nuclear fuel cladding in nuclear reactors.Investigation on the initial oxidation behavior of zirconium alloys in low vacuum environment is helpful to understand the oxidation mechanism of zirconium alloys.Zr-0.75Sn-0.35Fe-0.15Cr,Zr-0.75Sn-0.35Fe-0.15Cr-0.15Nb and Zr-1.5Sn-0.35Fe-0.15Cr(wt%)alloys were made into large-grained samples,and then TEM thin samples were prepared by electrolytic double-spraying.By studying the oxidation of TEM large-grained samples in a vacuum tube furnace with a vacuum of 3 Pa at 280°C and 290°C,the effect of Sn and Nb on the initial oxidation behavior of zirconium alloys were investigated,and the nucleation and growth of ZrO2 grains on the surface of the alloys was also observed.The results show that the addition of Nb or the increase of Sn content promotes the nucleation and growth of ZrO2 grains formed on Zr-0.75Sn-0.35Fe-0.15Cr alloy oxidized at 280°C and 290°C in low vacuum environment.When oxidizing at 280°C/30 min under low vacuum conditions,the addition of Nb promotes the increase of ZrO2 grain size,while the increase of Sn content makes the ZrO2 grain change from spherical to short rod.With the increase of oxidation temperature(290°C/30 min),the ZrO2 grains on the surface of the Zr-0.75Sn-0.35Fe-0.15Cr and Zr-1.5Sn-0.35Fe-0.15Cr alloy grow up,while the ZrO2 grains on the Zr-0.75Sn-0.35Fe-0.15Cr-0.15Nb alloy has a faster nucleation rate.