Effect of microstructure and alloying elements distribution on welding quality of Zircaloy-4

17th IUMRS International Conference in Asia

Ji, Pengbo^1 ; Du, Yanhua^1 ; Chi, Chunxia^1 ; Wang, Hongbo^1

China North Nuclear Fuel Co. Ltd., Inner Mongolia Baotou

014035, China^1

关键词: Elements distribution;    Hexagonal close-packed (hcp) structures;    Second phase particles;    Trace amounts;    Welding line;    Welding process;    Welding quality;    X ray diffractometers;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/182/1/012020/pdf
DOI  :  10.1088/1757-899X/182/1/012020

来源: IOP

【 摘 要 】

In order to understanding the appearance of the abnormal welding line during the CANDU fuel element end plug welding process, the analysis on the microstructure and the alloying elements distribution of three different batches of Zircaloy-4 rods, named as A753, B592 and C744, was carried out in the present study. The microstructure and localized composition of the alloys were studied by optical microscopy, X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM) and energy disperse spectroscopy (EDS). The results showed that there was no obvious difference among the three specimens. However, it was found that there appeared etch pits in the middle area of A753 batch samples. And the grain size of welding qualified C744 batch sample was greater than the un-qualified samples of A753 and B592. According to HRTEM and EDS results, the second phase particles in the Zircaloy-4 were Zr(Fe, Cr)2phase with the Hexagonal Close-Packed (HCP) structure. The matrix belonged to α-Zr phase with the Hexagonal Close-Packed (HCP) structure. The second phase particles distributed inside the grains and at the grain boundaries of the three batches of the alloys. The size of the second phase particles in qualified sample C744 was around 200nm with the elements of Zr, Fe and Cr. However the size of the second phase particles in the un-qualified samples B592 and A753 was about 100nm, in which the elements of Fe and Cr could not be detected or only trace amount of Fe could be detected for part of the second phase particles. Therefore it may be concluded that the grain size, the second phase size and composition are the main factors to affect the welding quality of the alloy.