Zr-0.75Sn-0.35Fe-0.15Cr-xNb合金在He+辐照下的显微组织演变及其对腐蚀行为的影响

Microstructural Evolution under He+ Irradiation and its Effect on Corrosion Behavior of Zr-0.75Sn-0.35Fe-0.15Cr-xNb Alloys

摘要:

本工作采用2 MeV He_⁺在300 ℃下对Zr-0.75Sn-0.35Fe-0.15Cr-xNb (x=0、1.0,wt%)合金进行辐照,然后在360 ℃/18.6 MPa/0.01 M LiOH水溶液中进行高压釜腐蚀实验,利用扫描电子显微镜和透射电子显微镜研究辐照对合金显微组织及腐蚀行为的影响。结果表明,添加Nb改变了Zr-0.75Sn-0.35Fe-0.15Cr合金中第二相的数量、尺寸和晶体结构。He_⁺辐照1 dpa后,合金的辐照损伤峰区域分布有大量的He泡和型位错环,添加Nb对He泡和位错环的数量及第二相的元素扩散等均产生了一定的影响。腐蚀结果表明,He_⁺辐照或添加1.0 wt%的Nb均可促进Zr-0.75Sn-0.35Fe-0.15Cr合金的腐蚀,但当二者同时存在时,辐照能减弱Nb促进腐蚀的作用。

Abstract:

Zirconium alloys used as fuel claddings in water-cooled nuclear reactors generally serve in a harsh environment of high-temperature high-pressure water and strong neutron irradiation. Nb is known to play an important role in improving the corrosion resistance of zirconium alloys. Therefore, studying the microstructural changes and its effect on the corrosion behavior of zirconium alloys with different Nb contents before and after irradiation can provide a basis for the design of advanced zirconium alloys. In this work, Zr-0.75Sn-0.35Fe-0.15Cr-xNb (x=0, 1.0, wt%) alloys were prepared and irradiated with 2 MeV He_⁺ at 300 ℃. The effects of irradiation on the microstructure and corrosion behavior of the alloys were investigated by using scanning electron microscope and transmission electron microscope. The corrosion environment was 360℃/18.6 MPa/0.01 M LiOH aqueous solution. The results revealed that the number, average size and crystal structure of the second phase particles in Zr-0.75Sn-0.35Fe-0.15Cr-xNb alloys changed with the increase of Nb content prior to irradiation. After He_⁺ irradiation to 1 dpa, however, a large number of He bubbles and -type dislocation loops were induced in the radiation damage peak region in the alloys. To some extent, addition of Nb can affect the number of He bubbles and dislocation loops and elemental diffusion from the second phase particles. The corrosion results showed that He_⁺ irradiation or addition of 1.0wt% Nb could accelerate the corrosion of Zr-0.75Sn-0.35Fe-0.15Cr alloy, but the irradiation could reduce the acceleration effect of Nb on the corrosion of Zr-0.75Sn-0.35Fe-0.15Cr alloy.