Xe离子辐照对Zr-1Nb合金表面形貌及电化学腐蚀特性的影响

Influence of Xe Ion Irradiation on Surface Morphology and Electrochemical Corrosion Behavior of Zr-1Nb Alloy

锆合金包壳在反应堆环境下受到辐照与腐蚀的协同作用。本工作使用6.37 MeV Xe离子辐照Zr-1Nb合金,评估了常温0.5mol/LLiOH水环境中辐照前后Zr-1Nb合金的电化学腐蚀特性,并测量了辐照前后Zr-1Nb合金的显微硬度和表面形貌、物相组成。经过Xe离子辐照后,Zr-1Nb合金表面出现了离子剥蚀形成的凹凸起伏,硬度和表面粗糙度随辐照剂量增加而增加。0.5dpa剂量辐照后样品的腐蚀电流密度相比于未辐照样品增加约18倍,2.7dpa剂量样品则增加约82倍。同时,辐照后样品的腐蚀电位降低,极化电阻显著减小。此外,辐照后Zr-1Nb合金样品低频阻抗降低,容抗弧半径也随辐照剂量增加而减小。极化曲线和电化学阻抗测量结果表明,离子辐照增强了Zr-1Nb合金的腐蚀倾向,其耐腐蚀性能随辐照剂量增加而降低。电化学腐蚀测试后,Zr-1Nb合金表面出现了板条形组织,且离子辐照后样品该板条形组织更加细小。Zr-1Nb合金辐照样品耐腐蚀性能下降主要是合金基体的辐照损伤导致的结果。

Zirconium alloy cladding suffers from the synergetic effect of irradiation and corrosion degradations in reactor environment.In order to evaluate the effect of irradiation on the electrochemical corrosion behavior of the Zr-1Nb alloy before and after irradiation in 0.5 mol/L LiOH solution at room temperature,the alloy was irradiated with 6.37 MeV Xe ions.The microhardness,surface morphology and phase composition of Zr-1Nb alloy before and after irradiation were measured.After the Xe ion irradiation,the surface of Zr-1Nb alloy has a bump formed by ion denudation.The microhardness and surface roughness are increased with the increase in irradiation dose.The polarization current density of the 0.5 dpa dose irradiated sample is increased by 18 times than that of the unirradiated sample,while it is about 82 times higher of the 2.7 dpa irradiated sample,compared with the unirradiated sample.After the ion irradiation tests,the polarization potential and polarization resistance of the samples decrease significantly.In addition,the lower-frequency impedance is decreased,and the curvature radius of the capacitance curve is also decreased with the increase in irradiation dose.The polarization curves and EIS results show that the ion irradiation increases the corrosion tendency of the Zr-1Nb alloy,and its corrosion resistance is decreased with the increase in irradiation dose.After electrochemical corrosion test,the surface of Zr-1Nb alloy has a strip structure,and the strip is finer after ion irradiation.The reduced corrosion resistance after the ion irradiation tests is considered to be mainly caused by the irradiation induced damage on the alloy matrix.