材料期刊网

选用了具有相同织构的Zr-4, N18和ZIRLO锆合金片状样品, 利用高压釜在360℃,  18.6 MPa的0.01 mol/L LiOH水溶液中进行了280 d腐蚀实验, 采用EBSD和SEM研究了织构及合金成分对锆合金耐腐蚀性能的影响. 结果表明, 腐蚀280 d后, Zr-4样品表现出明显的腐蚀各向异性特征, 在织构因子较大的轧面(S_N面)上氧化膜较厚, 耐腐蚀性能差, 而在织构因子较小的垂直于轧向的截面(S_R面)和垂直于横向的截面(S_T面)上氧化膜较薄, 耐腐蚀性能好. 添加合金元素Nb的N18和ZIRLO样品氧化膜生长的各向异性受到抑制, 在S_N, S_R和S_T 3个不同面上氧化膜的厚度相同, 耐腐蚀性能比Zr-4样品的S_N面优良. 但是, 如果只以样品的S_R和S_T面进行比较, 氧化膜的生长速率会随Nb含量的增加而增大, 耐腐蚀性能变差. 从改善合金的耐腐蚀性能考虑, Nb的添加量不应该高于0.3%(质量分数).

Zirconium alloys of a hexagonal close--packed crystal structure have prominent anisotropic characteristic in comparison with metals of a cubic crystal structure and a strong texture is produced in sheet or tubular materials during the fabrication process. The anisotropic characteristic is bound to be reflected on the corrosion behavior of zirconium alloys. In order to investigate the effect of texture and compositions on the anisotropic growth of oxide layer formed on zirconium alloys and clarify the mechanism of improving corrosion resistance by adding Nb in zirconium alloys, Zr-4, N18 and ZIRLO zirconium alloys with different contents of Nb were adopted as the experimental materials. All the plate specimens of zirconium alloys 2 mm in thickness have a similar texture. Corrosion tests were carried out in a static autoclave at 360 ℃, 18.6 MPa in lithiated water with 0.01 mol/L LiOH. The results show that the anisotropic growth of oxide layer on different surfaces of the specimens was only observed for Zr-4 specimen but not for N18 and ZIRLO specimens. The thickness of oxide layer develops much faster on the rolling surface (S_N surface) than that on the surface perpendicular to the rolling direction (S_R surface) and the surface perpendicular to the transversal direction (S_T surface) for Zr-4 specimen after 90-100 d exposure, and the corrosion resistance on the S_R and S_T surfaces was much better than that on the S_N surface. However, for N18 and ZIRLO specimens the anisotropic growth of oxide layer was restrained by the addition of Nb, and the oxide thickness on these three different surfaces was the same after 280 d exposure. Therefore the corrosion resistance of N18 and ZIRLO sheet or tubular specimens was superior to Zr-4 corroded in lithiated water, because the oxide layers grew mainly on the S_N surface of the specimens. If making a comparison among Zr-4, N18 and ZIRLO specimens about the growth rate of oxide layers only on the S_R and S_T surfaces, it is shown that the growth rate of oxide layers increased with the increase of Nb content in these alloys. From a point of view for the improving corrosion resistance, the addition of Nb no more than 0.3\% (mass fraction) is recommended.